them is not so obvious. When it is applied to the skin, some one of its
principles is probably absorbed. Pitch, as a remedy for Lepra, is
comparatively of recent introduction, but its efficacy has already been
very widely acknowledged.

Tincture of Cantharides and Acetate of Potash, both diuretics, have been
employed in Lepra to eliminate the _materies morbi_ from the blood into
the urine, and have sometimes appeared to succeed in so doing. But in
this, as in many other cases, counteraction is both easier and more
certain than elimination. The system itself naturally attempts this
elimination, and when it finds it impossible, we often gain nothing by
urging it.

I need scarcely say that these remedies are applicable only in simple
Lepra and Psoriasis, and not in the syphilitic forms of those eruptions,
which are treated best by Mercury, or by other medicines of the second
order of Catalytics. These Syphilitic eruptions are distinguished by a
coppery or a livid-grayish colour, and by the absence of itching.

Sulphur has been used with benefit in Eczema, Impetigo, and Lepra. It
may be administered externally in the form of fumigation or ointment, or
internally in combination with an alkali or with Iodine. In the case of
Eczema and Impetigo, the fumigation and internal administration are
preferable, as the ointment is apt to increase the existing irritation.
In the cure of Lepra the mineral waters of Harrowgate and other places,
containing Sulphuretted Hydrogen gas, have been much recommended. Thus
we have in Sulphur a third Antisquamic medicine. It is more or less
useful in all non-syphilitic cutaneous disorders. Dr. Burgess has found
sulphur ointment and fumigations to be very useful in Psoriasis
palmaris. (_On Eruptions of the Face, etc., p._ 229.)

Though Sulphur seems to act specifically in the treatment of these
disorders, there is another disease of a similar kind which it has been
supposed to cure by a mere external agency. This is Scabies. Some have
fancied that even here it acted specifically, and that this also was a
blood-disease. But Scabies has long been attributed to an external
cause, an insect, or, more correctly, an arachnid, which, by burrowing
in the skin, is thought to produce the vesicular eruption. The Acarus
Scabiei, or Itch insect, was discovered in 1179 by Abenzoar, the
Arabian. In 1687 Dr. Giovanni Bonomo wrote a full account of it in a
letter to Redi of Florence. It is supposed that Sulphur ointments and
Sulphur fumigations have a direct external action in causing the death
of this Acarus, by the bodily transmission of which from one person to
another the contagious nature of the disease is accounted for.

Dr. Billing considers that the confirmation of this discovery has given
the death-blow to an idea which will probably last as long as medicine;
viz., that certain remedies exert a special influence in the cure of
particular diseases. (_Principles of Medicine_, p. 75.) But we must not
deny the existence of special agents, simply because we cannot
understand their operation; for it is apparent in too many instances.
And from the circumstance that Sulphur has proved beneficial when given
internally in Scabies, as well as the fact that this disease has often
an idiopathic origin, I am still disposed to doubt the value of the
inference which is drawn from the discovery of the Acarus, and inclined
to believe that Sulphur may exert an action of a specific kind in this
disease as well as in the others.

Some other internal remedies, and many other external applications, have
been used in Skin diseases; but these that I have mentioned are the only
ones that appear to exert something of a special action in all cases.
Arsenic is perhaps the most universal in its application. It often
happens that when this remedy entirely fails, the eruption is connected
with a constitutional taint of Syphilis. When there is a suspicion of
this, such a remedy as Donovan's solution, containing both Arsenic and
Mercury, is peculiarly applicable, because capable of acting in a double
way. This medicine also contains Iodine; and either this preparation, or
the Iodide of Potassium, should be prescribed when the skin disease
appears to be connected with a strumous diathesis.

As soon as the course of Arsenic is found to produce swelling of the
face, or irritation of the conjunctivæ, symptoms which denote the
saturation of the system with the remedy, its administration should be
suspended for a while.

We have now concluded the subject of Hæmatic medicines. I have said that
this class has been very generally neglected and overlooked by writers
on the subject. For this reason, and because there are some ideas
respecting their action which I have thought it worth while to work out
and to investigate at some length, I have devoted more space to its
elaboration than I shall be able to spare for either of the remaining
classes, in the consideration of which we are not likely to encounter so
many interesting and debateable points.

PROP. VIII.--_That a second class of medicines, called_ NEUROTICS, _act
by passing from the blood to the nerves or nerve-centres, which they
influence._

1. _That of these, some, called_ STIMULANTS, _act so as to exalt nervous
force in general or in particular._

2. _That others, called_ NARCOTICS, _act so as first to exalt nervous
force, and then to depress it; and have also a special influence on the
intellectual part of the brain._

3. _That others again, called_ SEDATIVES, _act so as to depress nervous
force, in general or in particular._

Having investigated at some length the action of Blood-medicines, we now
commence the consideration of another class of remedies, which differ
very widely from the last in their mode of operation.

The action of Hæmatics is slow, but more or less durable, because it is
evidenced in the blood; and a change in the blood produced by this
action continues for a longer or a shorter time.

The action of Neurotics, or Nerve-medicines, is rapid; but it is
transient, and is soon over. A Neurotic medicine does not cause any
change in the blood; and it cannot remain in it, but soon passes out. It
acts by contact with nerve, apparently producing no lasting change even
in nerve-fibre; and as the cause of the action cannot remain, the effect
also soon passes away. Whereas Hæmatics, durable agents in the blood,
are used to counteract the causes of inveterate and chronic disorders;
these Neurotics, which produce a transitory, but more or less forcible
impression on the nervous system, are employed to rouse it when torpid,
or to depress it when over-excited. Rarely of use in chronic
blood-disorders, they are given mostly in the temporary emergencies of
acute diseases. But it is obvious that even a temporary agent may prove
of permanent efficacy by remedying a temporary emergency.

It was feasible to attempt some explanation of the actions of medicines
in the blood, occasionally more or less analogous to known chemical
influences. But the agency of nerve-medicines is of a far more
incomprehensible kind. When we consider that little or nothing is known,
or can be known, about the ultimate causes of sensation, or motion, or
nervous excitement, there is no need for wonder that we find ourselves
at a loss to explain the operation of medicines that influence these
conditions.

Thus I must chiefly limit my remarks on Neurotics to defining _what_
their action is, finding it impossible to state with certainty _how_
they act. And the field of inquiry being so limited, it follows that
there is much less to be said about them than had to be said of
Hæmatics.

Nearly all the powerful poisons that act after passage into the blood,
belong to this class. Their action in most points of view is such as
completely to exceed our means of comprehension.

Sudden death may be produced by it. But there is no apparent cause for
this. We find no erosion or perforation of the coats of the stomach or
intestines; no mechanical disorganization of the tissues, or chemical
change in them; no hæmorrhage, or vascular disease; no rupture of
nerve-fibres. Whence, then, could death have arisen? How could the mere
presence of a few atoms in the blood,--half a grain, one-twentieth, or
even one-fiftieth of a grain--how could this apparently contemptible
influence have produced so essential a derangement of the vital
functions as to stop them altogether? It is impossible to answer.

The action of such remedies in the sudden causation or alleviation of
nervous symptoms, when applied in the cure of disease, is equally
wonderful. How are we to account for their different actions on
different nerves? How is it that Opium contracts the pupil, and
Belladonna dilates it?--that Digitalis affects the heart, and Stramonium
the respiration?--that Prussic acid will cause convulsions, and
Hyoscyamus delirium? In what way are these various operations brought to
pass? It is impossible to answer.

Though it is, I say, quite impossible to frame for any one of these
questions a certain or satisfactory reply, on account of the manifest
insufficiency of our acquaintance with the details of such actions as
these, yet I must now venture to repeat an idea which I have already
referred to at the commencement of this Essay (p. 46,) and state my
belief in the bare possibility of the operations of Neurotic agents
being explicable upon mechanical grounds. It is generally believed among
scientific men that each particle of a compound body is made up of a
number of indivisible atoms, each of which is inconceivably minute in
size. And as these compound bodies have each a peculiar chemical
constitution, so must each of their ultimate parts be composed of a
peculiar arrangement of simpler atoms, and thus have a certain shape of
its own more or less different from the shape of every other compound
atom. Both the substance of a nerve, and the active part of a
nerve-medicine, consist of a number of definite compound atoms. And it
is possible that the atom of a stimulant medicine may be of such a shape
as that it shall be unable to coincide with, or to fit into, the series
of atoms forming the sensitive surface of the nerve, and thus irritate
this when brought into contact with it; and that the compound atoms of a
sedative may so arrange with these nerve particles as to fit among and
extinguish their salient points, and annihilate their natural
sensibility. We learn from the phenomena of the senses that the nerves
are very much under the influence of mechanical impulses of all kinds,
and particularly minute and inappreciable impulses of this description.
Another fact which gives additional credibility to such an idea is, that
those Neurotic substances which are chemically alike are in general
alike also in their influence on nerve.

The particular way in which nerve-medicines affect different parts of
the nervous system might perhaps be explained by supposing minute
chemical differences in the composition of the atoms of which those
parts are constructed, sufficient to alter their relations to the atoms
of certain remedies. If we adopt the Atomic theory, we must perceive
that no two chemical bodies can be precisely alike in the shapes of
their particles. This various dissimilarity might throw some light upon
the many shades of distinction between the operations of Neurotic
medicines on different parts. Thus, as a general rule, both Morphia and
Atropia are paralyzers of motor nerves. But they do not act alike on the
Ciliary nerves by which the motions of the Iris are controlled. We may
suppose that there is a certain chemical peculiarity in the particles of
these nerves, by which they are enabled to coincide with the atoms of
Atropia, and are thus blunted and paralyzed by them; but are, on the
contrary, stimulated and excited by the atoms of Morphia, which have the
contrary action, because unable, on account of their relative shape, to
dove-tail with these atoms.

This idea is, as I have said, purely conjectural and fictitious, and is
indeed likely to remain so; for the thing is not by its nature
susceptible of proof, nor is it even possible to inquire into it. And I
have only thought it worth while to explain it at length because it is
desirable that every statement which is made, however improbable and
unworthy of credence it may seem, should at least be placed in as clear
a light as possible.

The action of a Neurotic is readily distinguished from that of Hæmatic
medicines by the fact of its exerting a rapid and well marked influence
of some kind on the nervous system. As it is impossible that the
medicines contained in this class should remain in the blood, they
therefore pass out of the blood through the glands, and in so doing
generally act as Eliminatives. This, their secondary action, will be
subsequently considered. It is generally of less importance than their
action on nerve; with the exception of some which, as volatile oils and
resins, exert a very feeble Neurotic action, but are comparatively
powerful as Eliminatives. In this case the secondary action becomes the
more important of the two.

The most dangerous symptoms of disease are evidenced in the nervous
system. Neurotics are employed to control these symptoms as they arise,
but Hæmatics are used to combat the cause of the disorder. As to their
relative efficacy, there is an advantage and a disadvantage on each
side. On the one hand, nerve-medicines are more numerous and more
powerful than blood-medicines, and thus in the control of symptoms they
are wielded with more immediate certainty than the others in the
counteraction of diseases. On the other hand, the symptom that is
dreaded is only relieved for a time by the Neurotic remedy, while the
morbid condition that caused it continues, and will perhaps cause it
again; but when a disorder is remedied by the employment of Hæmatic
medicines, it is more or less permanently cured and put an end to.

In the above Proposition I have endeavoured to state as much as we know
with certainty of the action of Neurotics. To this certainty I have
already ventured to add a surmise, on which no certain reliance can be
placed. But even if the theory of the action by atomic shapes should be
rejected as improbable, because affording too easy an explanation of a
naturally inscrutable operation, it would still seem likely that these
medicines may take effect by exerting some minute and imperceptible
influence on nerve-fibre, or producing in it some inappreciable
disorganization or change, which has the effect of altering the natural
performance of its functions. The effect of mechanical concussion or
shock, which may produce death by minutely disarranging the particles of
the nervous centres, presents an obvious analogy to the sudden and
remarkable action of some nerve-poisons.

Having offered these vague suggestions as to the ultimate _modus
operandi_ of Neurotics, I will now proceed to divide the Proposition in
which their more obvious action has been stated into a number of minor
propositions. These apply to the whole class. The three divisions will
be afterwards shortly considered separately.

    _m. p. 1._--That Neurotics are medicines which pass into the
                      blood.

    _m. p. 2._--That their action is evidenced by a change in one
                      or more of those functions which are attributed
                      to the nervous system.

    _m. p. 3._--That it is necessary that they should pass from the
                      blood to that part of the nervous system which
                      is influenced by them.

    _m. p. 4._--That they are of use in an over-excited or depressed
                      state of the nervous system.

    _m. p. 5._--That they are transitory in action, and cannot remain
                      in the blood.

Some space and labour was required in the proof of the minor
propositions relating to Hæmatics, for among them were included some
things that are not universally acknowledged; but the above account of
the action of Neurotics concerns matters that are very generally
admitted, and will not occupy us nearly so long in its discussion.

In the first place it is affirmed that Neurotic medicines pass into the
blood. In the consideration of Prop. II., it was shown that all of
them,--whether vegetable alkaloids, volatile oils, resins, or mineral
substances,--were more or less capable of being absorbed. That they do
pass into the blood is proved by the fact that many of them have been
detected there, as well as found in the secretions into which they must
have entered from the blood. Ammonia, Hydrocyanic acid, Antimony,
Assaf[oe]tida, Turpentine, Alcohol, and Camphor,--all of which are
Neurotic agents,--have been chemically detected in the blood by
Tiedemann and Gmelin. A still larger number have been discovered in the
urine by Wöhler, particularly of volatile oils and odorous principles.
The active principles of Opium, Belladonna, Stramonium, and Henbane,
have been detected in the same secretion by others.

Thus Neurotics pass into the blood. That they act after this absorption,
and not by contact with the mucous surface, was proved in the
consideration of Prop. I.

The second minor proposition is borne out even by the names by which the
recognised action of these medicines is distinguished. Considered as a
class, they have no action on the blood, but their influence is quickly
and obviously exerted on the nervous system, or on the vital functions
which are universally attributed to that part of the animal frame.
Stimulants are so called because they are found by experience to exalt
nervous force; Sedatives, because they depress it. Thus Ammonia is given
to prevent Syncope, caused by a weakness or failure in power of the
nerves of the heart; and Aconite is prescribed to relieve pain caused by
an over-excitement of the sensory nerves. Though in these examples
Ammonia acts on the centre, and Aconite on the peripheral nerves, yet
they are both capable of exalting or of depressing nervous force in
general. But neither Stimulants nor Sedatives, as defined by me, exert
any marked influence on the intellectual part of the brain. They do not
affect the phenomena of mind, or of the four special senses which are
immediately associated with it. This influence is confined to the
intermediate division of Nerve-medicines, called Narcotics. Their
general action is evidenced by a short or long primary stimulation,--and
a subsequent depression of nervous force, which is also of variable
intensity. At the same time they affect the mind in various ways;
exciting it, confusing it or lulling it. Opium and Alcohol are examples
of Narcotics. These distinctions are in most cases obvious and well
defined.[42]

The third minor proposition repeats the rule of local access, which has
already been enforced in treating of the fifth proposition. It was not
necessary to maintain this in the case of medicines acting on the blood;
but Neurotic agents must be shown to operate locally on the various
nervous organs. I have only to repeat the arguments which were urged
before. It is proved that the action of nerve-medicines cannot be
propagated by nervous connexion, but that passage in the circulation is
necessary; that the course of the latter is sufficiently rapid to
account even for the action of Hydrocyanic acid; and that, however near
a medicine be introduced to a nervous organ, it does not affect it
unless it be allowed to reach it. The nerves are not naturally
constituted for the conduction of medicinal impressions, but only for
the passage of impulses of volition, sensation, or emotion. And this
evidently forms a powerful safeguard to the system against the effects
of a poison. The assertion is further maintained by the fact that the
action of a Neurotic, when applied topically to the part which it tends
to influence, is the same as that which is exerted by it on the same
part after absorption. And lastly, some nerve-medicines have actually
been found after death in the substance of those nerves and centres
which had been affected by them during life.

The use of these medicines in the treatment of disease is defined in the
fourth minor proposition. They have no influence in the blood. They are
not employed in slow or long continuing diseases. Their applications
depend on their known physiological tendencies, already stated. Abnormal
deviations from the proper functions of the nervous system are rectified
by means of the influence which they exert over the nervous organs.

When the powers of life are sinking, the nervous force on which life
depends may perhaps be roused by a strong Stimulant, and maintained by
its repetition. Sometimes the emergency may be thus postponed, and the
danger escaped.

In violent inflammations and fevers, when the action of the heart is so
violent, and the nerves that control it so excited, as to place life in
peril, we may do good by the administration of a Sedative, such as
Antimony or Digitalis, by which the nervous force may be reduced to its
proper level.

Narcotics are used in various cases, to cause sleep, or to quiet mental
irritability. Both these and Sedatives are employed to alleviate the
different kinds of pain.

Neurotics are thus applied to various symptoms, and to many disorders.
Their different modes of action will be detailed more at length
presently. It must be remembered that all these actions, powerful though
they may be, are transitory. The effect produced on the nerve is not a
lasting one, and no essential change in the blood is effected by true
Neurotics. They are not natural elements of this fluid, but must quickly
pass out of it; and they having thus left it, their action also is over.
Thus the truth of the fifth minor proposition is plain.

I will now attempt to give a brief but distinct account of the three
divisions into which I have divided this class of medicines.

STIMULANTS.

Stimulants are medicines which pass from the blood to the nerves or
nerve-centres, and act on them so as to exalt nervous force, in general
or in particular. That is, they may extend their operation more or less
to the whole nervous system, having a general tendency to communicate
nervous energy; or they may confine their action to particular
departments of this system, having no manifest influence on other parts.
On referring to the arrangement at the commencement of the Essay, it
will be seen that Stimulants are subdivided, according to whether their
action is thus extended or confined.

    STIMULANTIA.

    Ord. 1. Stimulantia generalia.
    Ord. 2. Stimulantia specifica.

The first order includes all the medicines that are commonly understood
to be Stimulants. But as the remedies of the second order obviously
exalt nervous force, the term applied to the others on that ground could
not consistently be withheld from them, although their action is more
limited and local in its nature, being confined to a certain part of the
body, and to certain nerves. The same remark may be made of the order of
Special Sedatives, which will soon have to be considered.

ORD. I. GENERAL STIMULANTS.

(_Mineral substances._--Ammonia and its Carbonates. Phosphorus.

_Animal substances._--Musk, and Castor.

_Vegetables containing volatile oils._--The aromatic Labiatæ, Compositæ,
and Umbelliferæ. Cloves and Nutmeg. Cinnamon, Cassia, Sassafras. Rue,
Barosma. The Aurantiaceæ. Canella. Valerian. Mustard. Cajeput and
Pimenta. Hops. Juniper, Turpentine. Cardamom. Onion.

_Vegetables containing acrid principles._--Senega. Horseradish.
Serpentary. Cascarilla. Pepper. Contrajerva. Ginger. Capsicum. Mezereon.

_Resinous substances._--Guaiacum. Mastich, Olibanum, Myrrh, Elemi.
Copaiba. Peru, Tolu. Assaf[oe]tida, Ammoniacum, Galbanum. Benzoin,
Storax. Pine resin.)

This list of General Stimulants is long, but it might even be further
extended. The majority are produced by the vegetable kingdom. The acrid
principles to which some owe their power are intermediate in nature
between volatile oils and resins. Some of them are volatile, like the
former; others fixed, like the latter. Some of the resinous products
contain also a volatile oil. The principles of Capsicum and Mezereon are
very similar in their chemical nature to the true resins. (_Vide_ page
85.)

These remedies differ very much in power, but their influence is the
same in character. They exalt nervous force in general. They seem to act
on the whole nervous system; but their most obvious action is to
increase the force and frequency of the pulse, and to invigorate the
circulation. They are not, for the most part, very powerful medicines;
and their action is seldom so violent as to be succeeded by much
reaction. They improve digestion for a time, by a stimulation of the
sympathetic nerves of the stomach and other viscera. In large doses they
are irritants, and may impair the digestive powers, and cause headache.
Though possessing no marked stimulant power over the function of mind,
like that of the Inebriant Narcotics, yet they certainly exalt the
activity of the brain, along with the other nervous forces.

Dr. Pereira classes the majority of Stimulants among _Ganglionics_,
considering that they only act on parts supplied by the sympathetic
system of nerves. But this view of their operation appears to me to be
too limited; for all of them seem to have a certain action on the brain.

Thus Ammonia is used in Syncope, a state which no doubt depends upon a
shock received by the brain. And there are several things which show
that it relieves this state more by stimulating the brain than by merely
rousing the heart and vascular system. It is found to be most effectual
when inhaled through the nose; by which means it could easily pass at
once into the cerebral circulation. Dr. Pereira thinks that when
administered in the liquid form it can only pass into the blood as a
salt, being neutralized by the stomach-acid. In this case it could only
act before absorption. But it is probable that it is too diffusible and
too rapidly absorbed to be entirely so neutralized; and besides, its
operation when inhaled is the same as when ingested, which seems to
point to an agency after absorption in the latter case. For when
inhaled, it must be absorbed in the free state. And to suppose that it
acts by stimulating the nerves of the stomach only, is to receive a
thing for which we find no parallel in the action of medicines. (_Vide
Prop. I._)

Ammonia has been used with advantage in the prevention of Epileptic
fits, being given just before their expected occurrence. It could hardly
be of use in this disorder unless it affected the brain.

Other General Stimulants manifest this action on the brain to a greater
or less degree.

Phosphorus is a Stimulant. In small doses it quickens the pulse. It
somewhat heightens the mental activity. It is said also to have an
aphrodisiac operation, due to its powers as a cerebral excitor. Volatile
oils possess a certain influence over the functions of the brain, as
well as those of the organic nerves. Cajeput oil has been used in
Hysteria; employed to control various spasmodic movements; and
administered in Typhoid fevers and Asiatic Cholera, to communicate
nervous power. The fetid gum resins are well known as Antispasmodics.
The spasms which these medicines relieve are due to a fault in the
nervous polarity, commencing generally in the brain or
nerve-centres,--and are more or less subdued by general stimulators of
the nervous functions. Copaiba, an oleo-resin, may cause a general
febrile condition, accompanied with headache,--when given in large
doses.

So obvious is the cerebral power of some volatile oils, that Turpentine,
in large doses, has been known to produce inebriation. It is not
generally used for its Neurotic powers, but as a Purgative or a
Diuretic; or else it might have been classed among Inebriant Narcotics.
I have enumerated it above among volatile oils. It may be regarded as
transitional between true Stimulants and Narcotics.

Ergot of Rye is another medicine which has a double action. It is used
as a Special Stimulant to the Uterus; but it is also a Narcotic to the
brain.

Most General Stimulants are without any marked influence on the mind;
but stimulate the organic and merely animal function of the brain, and
of the Sympathetic nerve throughout the system.

Concluding that General Stimulants have all more or less the power of
exalting nervous force in general, we have still to consider some other
questions relating to their action.

It is maintained by some that Stimulants have simply the power of
calling forth the nervous force which already exists in the system, and
that they cannot create any more in addition to this. But if this were
the case, then the reaction, or subsequent failure of nervous power,
ought to be exactly equivalent to the first temporary increase of that
power; assuming this increase to have been simply abstracted from the
natural resources. But we do not find it to be so. The reaction from the
effect of a Stimulant is always very slight, and often quite
imperceptible.

And there seems to be no _à priori_ reason why we should not actually
cause nervous force to be generated. We know that a galvanic current, or
even a mechanical cause, may induce it to be suddenly and powerfully
manifested. I believe that a Stimulant is able actually to produce
nervous action; perhaps by an irritative operation upon nerve-fibre. So
by continually repeating the dose of a Stimulant, as Ammonia or Brandy,
it is possible to maintain the circulation and nervous energy at a
certain level, without the occurrence of any reaction for a considerable
period.

But we must take care not to confound _nervous force_ with _vital
force_. The former may be very much increased, as in high inflammatory
fever, without a corresponding increase of the latter. The advantage of
a stimulant is regulated by this rule. When there is a failure in vital
energy, no Stimulant will serve to prolong life, for it cannot
communicate fresh vital power. But there may be no such failure of vital
energy, and yet a sudden or accidental deficiency of nervous force may
serve to peril the continuance of health, or even the tenure of life.
For a certain degree of this nervous force is necessary both for life
and health. When it is diminished, all the functions must suffer; when
it fails entirely, the circulation must stop, and death ensues. It is in
these cases that a Stimulant medicine is appropriate. It does not do
good by communicating vital energy, but by remedying the want of nervous
action, by which want the manifestation of the vital energy is subdued.
This must always be borne in mind when the applicability of Stimulants
is under consideration.

Some writers have complicated the subject by classing as Stimulants all
medicines which tend, directly or indirectly, to communicate vital
strength; as Tonics, and remedies which counteract morbid depressing
causes. This is in direct contradiction to the rule given above. True
Stimulants are only of use by counteracting that failure of nervous
force which hinders the manifestation of the vital strength which is
stored up somewhere in the system. For I have just observed, that to
exalt nervous force is not necessarily to exalt vital force, but that
any thing which tends to destroy the former must at length repress and
extinguish the latter.

The above considerations apply to the action of these Stimulants on the
powers of the system generally. But they may act locally. Thus in
moderate doses they promote digestion, by acting on the nerves of the
stomach and intestinal canal. They increase most of the secretions in
passing through the glands in the blood. In both cases they exalt
nervous force; but in the latter case their action is of a particular
nature, and will be treated of when they are considered under the title
of Eliminative medicines.

To impress the system generally, Stimulants are used when there is a
failure of nervous force on account of some sudden and acute disorder,
without any material undermining of the vital energies. In long chronic
cases, where there is real and manifest vital debility, Tonics or
blood-medicines are required. But in such a case as Syncope, or stoppage
of the heart on account of a sudden nervous shock, Stimulants are
particularly appropriate; also in the latter stage of Typhoid fever, or
of asthenic Pneumonia, or of Cholera, where the existence of life is
endangered by a great loss of nervous power. In spasmodic diseases, as
Hysteria, where the health is deteriorated on account of a derangement
of the nervous functions, Stimulants may be of use.

Such then appears to be the _modus operandi_, and such are the chief
applications, of the remedies belonging to the order of General
Stimulants. Those of the next order exert an action of the same kind,
but their field of operation is on a more confined scale.

ORD. II. SPECIAL STIMULANTS.

(Strychnia; Brucia; Toxicodendron; Ergot of Rye; Borax; Rue.)

These are medicines which pass from the blood to the nerves or
nerve-centres, and act so as to exalt the energy of particular nerves or
sets of nerves. They do not affect the whole nervous system, but they
operate on one set of nerves in the same way that General Stimulants
operate on all, though usually with greater energy.

The causes of such a localized action are hid in obscurity; but it has
already been hinted that they may perhaps be partly accounted for by the
differences in chemical or mechanical structure existing between
different parts of the nervous system.

Strychnia, the alkaloid and chief active principle of Nux Vomica, acts
as a Special Stimulant, chiefly to the spinal cord and the nerves that
proceed from it. Its operation is mainly exerted upon the motor
branches. Thus in large doses it causes a spasmodic and powerful
contraction of the muscles of the trunk, and may even produce death by
rendering respiration impossible. Its action is propagated from a motor
nerve to a muscle, and is kept up for some time. In small doses it is
useful in certain cases of paralysis. Two things are necessary in order
that it may act efficiently. The muscles of the part must be whole and
sound; for if destroyed by excessive atrophy or fatty degeneration, they
cannot be roused by any stimulus. The nerve, too, and the centre from
which it originates, must be sound, or else the medicinal impulse cannot
be conducted along it. These two conditions can only concur in paralysis
from disuse, _i.e._ when the incapacity to move a limb depends merely
upon its having long been in a state of inactivity, but when the lesion
of the centre which caused the paralysis has at length sufficiently
healed, and the nerve is now in a fit state to conduct a motor impulse.

Strychnia has no operation on the intellectual functions; neither does
it act upon the sympathetic nerves of the heart and arteries, so as to
quicken the pulse like ordinary stimulants. It exalts sensibility as
well as irritability, but not so powerfully. It is a special Stimulant
to the motor and sensory nerves throughout the body. Acting upon the
spinal cord, it tends thus to exalt reflex action, which is derived from
that centre. In small doses it appears to promote digestion, and may
perhaps act upon the ganglionic nerves supplied to the stomach.

Brucia, which is the other alkaloid of Nux Vomica,--and the leaves of
the Rhus Toxicodendron,--resemble Strychnia in their action, but are
less powerful.

Ergot of Rye is a stimulant to the muscular nerves of the Uterus of the
female, but to no other nerves in any marked degree. Borax and Rue
possess a similar action, but are not so efficient.

When labour is retarded on account of an atony or debility of the
Uterine muscle, and when also there is no obstruction or danger which
can result from bringing on contraction, Ergot supplies us with a ready
and effectual means of doing this. It is also efficacious in cases of
uterine hæmorrhage, because the open mouths of the bleeding veins in the
wall of the uterus are closed by the contraction which it causes.

When given in an over-dose, Ergot has a dangerous action on the brain,
producing at some times narcotism, at other times syncope. But this is
not the effect for which it is employed, and is altogether distinct from
its operation as a Special Stimulant, which is exerted only upon the
ganglionic nerves of the muscular uterus. In small doses it produces no
other effect than this.

Like the other medicines of this order, Ergot is not an excitor of the
heart and circulation. Its stimulant action is strictly local in its
nature.

NARCOTICS.

This, the second division of Neurotic medicines, is in one sense
intermediate between the other two divisions, but in another sense
different from both of them. Narcotics are defined to be medicines which
pass from the blood to the nerves or nerve-centres; which act so as
first to exalt nervous force, and then to depress it; and have also a
special action on the intellectual part of the brain.

This primary exaltation of nervous force is produced by some to a very
considerable extent, but by others very slightly. Of the three orders
into which I have divided Narcotics, which are named from their
respective actions upon the brain, Inebriants cause most, and Deliriants
least, of this primary stimulation. In the second place, Narcotics
depress nervous influence. This depression is not in a direct, but in an
inverse ratio to the primary stimulation. The less the one, the greater
the other. Thus the depression cannot be considered as the mere
re-action from the stimulation, as supposed by Dr. Brown, for then there
would be a direct relation between the two effects. But we find that the
exhilarating action of Alcohol may often be followed by no manifest
depression; and that Belladonna, which scarcely stimulates at all,
exerts a very sensible depressing influence.

Regarded simply in their action on nervous force generally, the
medicines of the first order of Narcotics would approach very nearly to
Stimulants, and those of the third order to Sedatives. But Narcotics
have all a power which is possessed by neither of the other divisions.

They influence the intellectual functions, _i.e._ the mind, and the
physical ties by which mind is connected with matter. These physical
ties are,--the functions of volition and sensation, by which the mind is
connected with the body, moving it or feeling it; and the five senses,
by which the mind, through the body, is connected with external things.
These intellectual properties, the centre of which is the brain, are
more or less affected by Narcotic medicines. The first action of the
latter is, to exalt these functions, just as they first exalt nervous
force in general. The degree of this exaltation varies, as in the former
case. Inebriants stimulate the mind to a considerable degree; Soporifics
less; and Deliriants possess least of this primary exciting power. But
it is in their secondary action on the mind that we find the most
characteristic difference between them.

On referring to the arrangement, it will be seen that I have divided
Narcotics into the three orders to which I have already referred by
name, and which are thus designated in Latin:

     NARCOTICA.

    Ord. 1. Inebriantia.
    Ord. 2. Somnifera.
    Ord. 3. Deliriantia.

These Orders are named from the secondary action of these different
Narcotics on the intellectual functions. In the production of
inebriation these functions are impaired and deranged; in sleep they are
lulled or extinguished for a time; and in delirium they are excited and
led astray. The several actions of these orders will be more minutely
described presently, and the individual medicines of which they are
composed will be shown to agree with the general definition of
Narcotics.

Dr. A. Billing considers that Stimulants call forth nervous force, and
Sedatives depress it; and that Narcotics do neither the one nor the
other, but merely impede its communication. I do not consider this
distinction to be quite correct. Narcotics exert in the first place a
stimulant, and in the second place a sedative action; but these actions
have no relation in degree, for one of them always exceeds the other, as
we have just seen. Thus in the whole effect, either the stimulation must
exceed the depression, or the depression must be greater than the
stimulation. So that in one way or the other the quality of nervous
influence must be altered.

The medicines of the first order of Narcotics resemble Stimulants so far
as this, that they tend altogether to increase the amount of nervous
force. Perhaps Tobacco and Lobelia are exceptions to this. The medicines
of the third order, and some of those in the second, tend on the whole
to diminish the quantity of nervous force, and are thus akin to
Sedatives. A correct understanding of the differences in action which
exist between the groups of Neurotic medicines is, I think, very
essential to a right application of these remedies in the treatment of
disease.

ORD. I. INEBRIANTIA.

(Alcohol; Wine; Ethers; Chloroform; Camphor; Indian Hemp; Tobacco;
Lobelia.)

The medicines of this order, taking Alcohol as the type, approach more
nearly to Stimulants than any other Narcotics. When given in small
doses, their narcotic operation may hardly be perceived. They are then
exhilarants; slightly quickening the pulse, and enlivening the mental
faculties. When given in large doses, this stimulating action on the
heart and mental powers occurs first, and is now more intense; but it is
soon succeeded by disturbance and impairment of the intellectual
functions. The secondary depression of the heart is comparatively
feeble, except in the case of Tobacco and Lobelia, which are exceptional
members of this order.

The disturbance of the mind produced by these medicines is not of a
partial, but of a general character, extending to all the intellectual
functions. It is called Inebriation, or drunkenness, and may exist in
various degrees. The mind itself is confused and bewildered; volition is
impaired, so that the man staggers in his walk; and the powers of the
senses are disordered or lost. This condition, when carried to an
excess, results in stupefaction, coma, and death. These are the several
degrees of the same action, which is a general impairment of all the
intellectual functions.

Alcohol and the Ethers produce the primary exhilaration in the greatest
degree; Tobacco and Lobelia, in the least. Though varying in degree,
yet, as far as the stage of inebriation, the effects of these medicines
are similar in kind.

Stupefaction constitutes the next stage of the action of Alcohol,
Camphor, Indian Hemp, Ether, and Chloroform. Camphor and Indian Hemp
exert at this period an anodyne influence; to which also, in the case of
Indian Hemp, may be added a very curious imitation of Catalepsy. Ether
and Chloroform have at this time a peculiar action in extinguishing the
sense of Feeling. With this object they are commonly administered by
inhalation in painful surgical operations.

The stupefaction produced by the above medicines is not at all prominent
in the case of Tobacco and Lobelia inflata. Instead of that they both
exert a particular sedative action on the heart and circulation. This is
accompanied with nausea, and with great relaxation of the muscular
system, like that which is produced by Antimony. It may lead to syncope
and death.

Syncope has been known to be suddenly produced in some cases of the
inhalation of Ether and Chloroform. These two medicines are also
muscular relaxers, like Tobacco.

The cases which demand the employment of these medicines, as also of the
other Narcotics and Sedatives, will be considered at the close of the
section treating of Neurotics, and again when some of them are
separately described in the fourth chapter.

ORD. II. SOPORIFICS.

(Opium. Lactuca. Hops. Nutmegs.)

Opium, which is the chief and only important medicine of this order, may
be considered as the type of Narcotics. It causes in the first place a
slight quickening of the pulse, and some excitement of the mental
faculties. It is named from its peculiar secondary action on the latter.
It produces drowsiness and sleep.

We have seen that the term _intellectual function_ must be understood to
include not only the mind itself, but also the powers of volition and
sensation, by which the mind is connected with the body,--and the five
senses, by which it is enabled to appreciate the external world.

Inebriants affect these three in about the same ratio. Ordinarily they
impair the mind, and derange the functions with which it is connected;
but they do not quite extinguish either volition, sensation, or the
special senses. Soporifics differ from this action in two ways. In sleep
the mind may remain active; but it is left alone, dreaming, and
uncontrolled by physical ties. For the functions of volition and
sensation, and the special senses of Sight, Hearing, Smell, and Taste,
are entirely suspended in perfect sleep. So that while Inebriants affect
similarly both the mind and the natural functions with which it is
connected, Soporifics may leave the first untouched, but they entirely
subdue the latter. The condition of sleep differs also in another
important particular from the state of inebriation,--as well as from
delirium, which we shall have presently to consider. Sleep is liable to
be suddenly interrupted or suspended by comparatively slight causes, as
a physical shock, or a forcible impression upon one of the senses which
are held in abeyance and subjection. Neither inebriation nor delirium
can be suddenly put an end to in this way.

Such appears to be the distinction between the operations of these two
orders of medicines.

Pain prevents sleep, because it enforces sensation. Thus a mere
Soporific, if effectual, would prove anodyne, and relieve pain.

But Opium has an important anodyne action, which is independent of its
power of producing sleep, for it may occur without the latter. It is by
far the best remedy for pain in the whole catalogue of medicines. It
also produces relaxation of the muscular system, and is thus a powerful
antispasmodic. In excessive dose it produces a marked sedative effect;
causing an imperceptible or irregular pulse, and very slow breathing,
with contraction of the pupil of the eye. It may kill by apn[oe]a;
_i.e._ by stopping the respiration.

Tobacco resembles Opium in causing contraction of the pupil, and
relaxation of muscular fibre. But it is inebriant, and not soporific;
and its secondary sedative action on the heart is more powerful than
that of Opium. The order of Deliriants dilate the pupil. Inebriants and
Deliriants act on the glands as Eliminatives, being mostly diuretic.
Opium has a contrary action; it diminishes all the secretions except
that of the skin, which it increases in amount. Most particularly it
diminishes the secretion of the bowels, causing constipation. At the
same time it impairs the appetite and digestive power, producing often
nausea, and coating the tongue. It tends also to produce a determination
of blood to the head.

Lettuce, from which Lactucarium is prepared, resembles Opium in its
action, but is neither so powerful nor so efficient. Nutmeg and Hops
have proved Soporifics when given in large doses.

The relief of pain, and the production of sleep, are about the commonest
and the most grateful of the offices which fall to the lot of the
physician; and in either case Opium, or one of its preparations, may be
said to be indispensable. But a certain caution and care must be
exercised, even in the administration of this most useful remedy. (_Vide
Art. Opium_, Chap. IV.)

ORD. III. DELIRIANTS.

(Hyoscyamus; Belladonna; Stramonium.)

These medicines are all produced by the natural order Solanaceæ. Of all
Narcotics they approach the nearest to Sedatives. Their only stimulating
action is to produce at the very first a slight and evanescent febrile
condition,--a quick pulse and heat of skin,--which never lasts long, and
is sometimes overlooked.

They are not Soporific. Their action is soon manifested by an anodyne
operation, and a sedative influence on the heart and circulation. For
this double action they are employed in medicine, being used in painful
disorders, fevers, and inflammations. As anodynes they are not so
efficacious as Opium, but their action is not followed by constipation,
or by a diminution in any of the secretions.

They all dilate the pupil of the eye. Belladonna produces a peculiar
dryness of the throat, and has been known to cause an erythematous
eruption. Stramonium appears especially to control the respiratory
nerves, and is thus used in Asthma, where there is a spasmodic circular
contraction of the smaller bronchial tubes. Lobelia, a medicine of the
first order, possesses a somewhat similar power. The action of the
remedies of this third order of Narcotics is distinguished by the
production of delirium when they are given in large doses.

Let us again assume the threefold division of the mental functions, to
which allusion has already been made. Inebriants impair equally the
mind, volition, and the five senses. Soporifics extinguish for awhile
both volition and the senses, but may leave the mind alone. In delirium
these functions are not thus impaired and held in subjection, but they
are excited and led astray. The mind is occupied intently upon imaginary
fancies; unreal objects and hallucinations are presented to the senses.
So that Deliriants, in this peculiar phase of their action, tend to
excite the mind and the volition, and to delude or derange the senses.

Speaking generally and rather inaccurately, we might say that the
medicines of the first order of Narcotics bewilder and impair the powers
of the mind; those of the second order subdue and extinguish them for
awhile; and those of the third kind excite and derange them.

Certain peculiar and exceptional effects are produced by some Narcotics
when they are administered in repeated doses for a long time together.
Taken in this way, Alcohol produces delirium tremens, and great
despondency of mind; as also often a chronic inflammation of the liver.
The continued smoking of Tobacco is found to exert a tranquilizing
influence over the mind. And the continual use of Opium or Indian Hemp,
both of which are habitually consumed in large quantities in the East,
produces a curious and melancholy series of mental hallucinations and
disorders.

SEDATIVES.

We have now to consider the third and last division of Neurotic
medicines. Sedatives are medicines which directly depress nervous force.
Some affect nervous force in general; others confine their action to
particular nerves. They are mostly energetic and dangerous agents. For
the time being they may destroy nervous power, and remove nervous
control.

It might already have been concluded, from what has been said of the
secondary action of Narcotics, that there are two ways in which a
Sedative action on nerve may be manifested. Sedatives may destroy
nervous influence; or they may simply derange it.

Let us suppose a special Sedative to derange the action of the Vagus
nerve. It would probably cause the rhythmical contraction of the heart
to be abnormally slow or irregular. It would be likely to diminish in
the lungs the sensation of want of breath, and thus decrease the number
of the respirations; and at the same time it would repress the
irritability of the pulmonary mucous surface. Further, it would in some
way derange the normal function of the stomach. All these things a
Sedative to the Vagus nerve does actually effect. Given in large
quantity, it may cause death, by destroying those functions which in a
small dose it deranges.

All the varieties in action of Sedative medicines may be accounted for
by considering that they may either derange or destroy the nervous
forces. In the case of each set of nerves in the body we may distinguish
an action of derangement, and an action of destruction, both producible
by Sedative medicines. Thus by an action on the motor nerves of the
cerebro-spinal system, convulsions or paralysis may be produced. By an
influence on the nerves of sensation; pain, or anæsthesia. By an
affection of the organic nerves of the heart, or of the brain which
controls them; palpitation, or syncope. By an action on the nerves of
the lungs; cough, or apn[oe]a. By the exertion of a sedative power over
those of the stomach, nausea may result, or vomiting. These various
symptoms are all brought about by Sedative medicines, but in each case
the first effect is referrible to a derangement, the second to a loss of
nervous power. In every instance there is an impairment of natural
nervous force.

Narcotics act on the mind. They cause death, with stupor or delirium.
Sedatives act on the organic function of the brain, which is necessary
to life, but they do not affect the mind. In poisonous doses, they kill
by producing syncope, which is a suspension of the action of the heart.
Hydrocyanic acid causes at the same time convulsions. These convulsions
appear to be caused by a derangement of the nervous polarity of the
spinal cord; and not by a stimulation of this centre, as the tonic spasm
of Strychnia. (_Vide_ page 232.)

Sedatives are divided into two orders, according to the extent of their
action; in the same way as Stimulants have been divided.

    SEDANTIA.

    Ord. 1. Sedantia Generalia.
    Ord. 2. Sedantia Specifica.

General Sedatives have a direct action upon all the nerves and
nerve-centres in the body, the result of which is a diminution of
nervous force.

Special Sedatives exert the same depressing action upon particular
nerves only. Like the order of Special Stimulants, they are peculiar
and exceptional agents. All those with which we are acquainted appear to
direct their action to the branches of the Vagus nerve.

It is among General Sedatives that the types or representatives of this
division are to be found. The definition of this order does not admit of
so great a variety in action as must be allowed to Narcotics. A
Stimulant medicine simply exalts or increases nervous force; and a
Sedative simply depresses the same. But a Narcotic first does one thing
and then the other; and according to the degrees of these two actions,
so do some Narcotics resemble Stimulants, and others approach very
nearly to Sedatives. But we have seen that Narcotics have also a
peculiar and mysterious action on the mind, which action is of three
separate kinds. And the same three orders which are named according to
their respective actions on the mind, are found to coincide with three
stages of transition from the action of a Stimulant to that of a
Sedative medicine.

It is impossible to associate in the same prescription a Stimulant and a
Sedative medicine; for their actions are directly contrary, and tend to
counteract one another. But it is often desirable to prescribe an
Inebriant Narcotic with a Stimulant, for their actions resemble each
other so much, that they are able to work together. And Deliriants,
which stand at the other end of the Narcotic scale, may often
advantageously be given with Sedatives, which they very much resemble in
their nervous operation. Thus, on the one head, Brandy may be given with
Ammonia; on the other hand, Hyoscyamus may be prescribed with Digitalis
or Hydrocyanic acid.

ORD. I. GENERAL SEDATIVES.

(Hydrocyanic acid. Creosote. Aconite. Conium. Colchicum. Tea and
Coffee.)

These are medicines which pass into the stomach, and are capable of
absorption; which are absorbed, and are proved to act after passage into
the blood. From the blood they pass to the nerves and nerve-centres, and
on all of them alike exert a depressing influence. Some of them are much
more powerful than others. They do not exert any primary stimulant
effect, or any action on the intellectual part of the brain. Most of
them have special actions and tendencies.

Hydrocyanic acid is a powerful and dangerous medicine. In large doses it
very rapidly takes effect, producing convulsions, syncope, and death. In
small doses it is anodyne, and antispasmodic. It is considered
especially to influence the reflex spinal system, and by this means may
allay convulsive cough, and quiet spasmodic movement. It is very useful
in Gastrodynia, and appears then to act locally upon the painful and
irritable nerves of the stomach.

Creosote stands, as a medicine, between Hydrocyanic acid and Turpentine.
It has a double action; being anodyne, like the former; and a mucous
stimulant, like the latter. Moreover, it is a true Astringent, which
cannot be said of Turpentine. It is not powerful as a Sedative, but its
peculiarity of action often renders it useful in Gastrodynia. It is
particularly applicable when pain in the stomach is accompanied with a
tendency to hæmorrhage, or with a probable relaxation of the mucous
coat.

Aconite is a powerful anæsthetic to the superficial sensory nerves. When
applied in solution or ointment to the surface of the skin, it produces
first some heat and tingling, which is attributable to a derangement of
the nervous influence; and this is succeeded by perfect numbness. It is
thus a most valuable topical remedy in true irritative Neuralgia. Other
Sedatives and Narcotics have the same power as topical anodynes, but not
in so marked a degree. In large doses Aconite is a General Sedative;
producing tingling of the extremities, vomiting, and syncope; and
affecting the brain in various ways, as will be shown by some
experiments which I have made upon its action, to be detailed in the
fourth chapter. An alkaloid called Aconitina, the most powerful of all
known medicines, is the active principle of this drug.

Conium (Hemlock) also owes its properties to the alkaloid Conia. Dr.
Christison has made some experiments upon the latter. He found that it
produced swiftly-spreading paralysis of the motor nerves; and he
considers it to act particularly as a Sedative to the reflex spinal
functions. It also paralyzes the sensory nerves, but in a less degree.

Conium is certainly anodyne; and produces often a sedative action on the
heart. It would thus appear to be a General Sedative. But in some
recorded cases of poisoning by Hemlock, coma has been mentioned as a
leading symptom. Were this to be authenticated, and shown to be the
invariable result of the action of this medicine in large doses, then it
ought certainly to be classed among Narcotics. Dr. Pereira considers it
likely that the plant contains more than one active principle. Hemlock
has a paralyzing action on the nerves of motion, which is directly the
reverse of the stimulating action of Strychnia; and is thus of use in
cases of convulsion and spasm. It is also often prescribed as an
anodyne.

Conium is further said to have a curious resolvent power over glandular
enlargements, and to have thus frequently caused their absorption and
disappearance. This action was first noticed and described by Dr.
Fothergill. All true resolvents operate by an action in the blood, but
it is difficult to conceive how such an action can be exerted by a
nerve-medicine. It may possibly act indirectly by quieting the action of
the heart, and controlling an irritable state of the nervous system. In
the same way Opium often appears to act as a resolvent. And it is
certain that Hemlock, when used for this purpose, very often fails
altogether. It has been wrongfully extolled as a panacea in Phthisis;
but is in fact of no greater use in that disorder than Hyoscyamus,
Prussic acid, and other medicines which reduce the pulse. For the
patient in this disease is devoured by a continual slow fever, and any
thing which tends to lower this fever will serve to prolong his
existence. But altogether it must be admitted that considerable mystery
attaches to the operation of this medicine.

Colchicum has many different actions. It has an agency in the blood,
being Antiarthritic. It is an Eliminative, acting on the liver and
bowels. And it is also a General Sedative. To the combination of an
eliminative with a sedative or anodyne action, the use of Colchicum in
Gout has been, I think, erroneously ascribed. For in fact it seems to
act best in this disorder when it causes no purging, and scarcely any
action on the nerves. When it has been long used, it causes a great
depression of the spirits, like that which may be caused by some
undoubted blood-medicines, as Mercury. But it does not affect the
understanding, or the special senses. In poisonous doses it depresses
the circulation and the nerves generally, but it causes no stupor or
insensibility. It is therefore not a Narcotic; but, like other
Sedatives, it kills by syncope.

In the behaviour of the system towards Colchicum, Aconite, Digitalis,
and other nerve-medicines, there are two peculiarities which are worthy
of remark. They are called _cumulation_ and _toleration_.

Some quantity of the medicine may often be given, in repeated doses for
some time together, without any apparent result. It seems to remain in
the blood, and to become accumulated or stored up there. But all on a
sudden it breaks out, appearing to be discharged on the nerves, and may
produce very dangerous symptoms. This _cumulative_ action is especially
observed of Digitalis, and therefore considerable care is required in
the exhibition of that medicine. This medicine is a Special Sedative,
and will be presently considered as such. In other cases we find that
the nervous system becomes by degrees inured to the effect of a
particular medicine, and suffers less by its presence than it did at
first. This is called _toleration_. It is particularly observed of
Colchicum and of Antimony, and of all medicines which act on the Vagus
nerve so as to cause vomiting.

Tea and Coffee, common articles of diet, are slightly sedative to the
nervous system generally. They lower the pulse, and, by diminishing
congestion of the brain, tend to clear and tranquilize the action of the
mind. This activity of thought is endangered by the cerebral congestion
which exists early in the morning, on account of recent sleep,--and
again towards the evening, from the full meal of the middle of the day.
It is thus at these times that they are found so useful, and are so
universally adopted. They are, in fact, almost indispensable to the
daily existence of civilized man, with whom a continual energy of mind
is a necessary of life. Infusions of these substances, or of materials
similar to them in medicinal nature, are adopted as a daily beverage by
all civilized nations. By diminishing congestion of the brain, Tea and
Coffee have not only the effect of clearing the mind, but in large
quantities they induce wakefulness. This is particularly the case with
Coffee. It is not clear that Tea, as commonly drunk, is ever
unwholesome. Green Tea is a more powerful sedative, and resembles
Coffee. Coffee has a more potent influence over the mind and nervous
system than is possessed by Tea, and is apt to disagree with many
persons. Like Opium, but in a far less degree, Coffee tends to confine
the bowels. By diminishing the congestion of the brain which is produced
by Opium, strong Coffee is of use in cases of poisoning by the latter
substance.

Tea and Coffee are sometimes said to be mental exhilarants; but they
only become so indirectly, by removing congestion, which is a cause of
stupidity.

Both Tea and Coffee contain the alkaloid Theine; but it is probable
that their Neurotic action is not so much owing to this, as to a
volatile oil, which exists in both in some quantity.

ORD. II. SPECIAL SEDATIVES.

(Antimonials. Ipecacuanha. Digitalis.)

These are medicines which, like the last, depress nervous force, yet
they do not exert their influence on the nervous system as a whole, but
only on certain parts of it. So far they resemble Special Stimulants;
but their effect is of a directly opposite nature. They have also no
direct influence on any part of the brain.

Antimony, Ipecacuanha, and Digitalis, have each of them a number of
different actions. The first has already been included among Catalytic
Hæmatics, as tending to counteract in the blood the process of
inflammation. But it possesses further a Neurotic power, by which it is
gifted indirectly with a more powerful control over acute inflammations
than could be exerted by any slow-acting blood-medicine. It is also
Eliminative. Passing out of the body through the glands of the skin, it
becomes a Diaphoretic. This may be its only action when it is given in
doses too small to act upon the nerves. It must not be confounded with
the diaphoresis which accompanies the condition of nausea, and which is
probably produced in another way. Ipecacuanha is in the first place a
Neurotic, of less power than Antimony; in the second place an
Eliminative, increasing expectoration, as well as Diaphoresis. Digitalis
too acts first upon the nervous system; then on the kidneys, being a
Diuretic.

But we are now concerned with the special Neurotic actions of this group
of medicines. They all exert an influence over the three functions of
respiration, circulation, and digestion. They affect the heart, lungs,
and stomach, parts which are supplied by the branches of the Vagus
nerve, as well as by the Sympathetic. Their action is not an external
action, for it is produced when they are introduced into the blood at
any part. Thus Tartar Emetic or Ipecacuanha, when injected in solution
into one of the veins, will cause vomiting. M. Magendie has found that
in the case of dogs they also produce Pneumonia. The mere inhalation of
the dust of Ipecacuanha has been found to act upon the lungs so as to
cause Bronchitis. These actions, as well as the various effects which
are found to follow the introduction of these medicines into the
stomach, can only be explained satisfactorily by supposing that they act
as Sedatives to the branches of the Vagus nerve, thereby deranging or
destroying the natural influence of that nerve in the direction and
regulation of the organs which it supplies. For we have already seen
that the action of a Sedative medicine is of such a nature as to derange
nervous force in some cases, and simply subdue it in others.

These actions are obviously nervous actions; for they are quick, sudden,
and transient, and confined to parts supplied by a particular nerve.
They are exerted upon nervous forces, and not upon the blood. If then
they are nervous operations, they must either be directed towards the
Vagus, or to the Sympathetic nerve, for these are the only nerves which
supply the parts influenced by these medicines. They cannot act upon the
Sympathetic, for two reasons. If they did so, we might reasonably expect
that the other parts of this nerve would be influenced at the same time.
But this does not appear to be the case. And again, an action upon the
Sympathetic nerve could not be suddenly and violently evidenced, for the
natural action of this nerve is slow, chronic, and persistent. At all
events, the effects for which they are used could not be produced by an
affection of this nerve.

We may therefore conclude that the action of these medicines is exerted
upon the Vagus nerve and its branches. They affect the different parts
of the Vagus nerve in variable proportion.

Some apparent anomalies in their physiological influence may be
explained by considering the peculiarities which attach to all sedative
actions. Thus we have seen that when given in large doses to healthy
persons, Hydrocyanic acid produces convulsions by deranging the reflex
spinal functions; and that in convulsive affections, when the same
functions are disordered, the same remedy may do good by subduing their
excited condition. On similar grounds, Tartar Emetic, injected into the
veins, may produce Pneumonia; and Ipecacuanha, introduced as dust into
the lungs, causes Bronchitis or Asthma; and yet Tartar Emetic is
advantageously employed in the cure of Pneumonia, and Ipecacuanha is a
remedy for Bronchitis. When the function of the healthy nerve, or that
part supplied to the lungs, is deranged to a certain degree, an
inflammation of the mucous membrane or substance of the lung is a
natural result. But when these tissues are already inflamed, a course of
medicine, which at the same time subdues the action of the heart, and
represses the irritability of the nerve supplied to the part will be
likely to effect a cure. They are both sedative actions; but the first
is an action of derangement, the second one of depression. This seems to
me to be the correct explanation of a difficult matter.

It was just now observed that these medicines affect the functions of
the Vagus in different proportions.

The action of Ipecacuanha, when given in repeated small doses, is
particularly directed to the pulmonary organs. It allays the sensation
of want of breath, and diminishes the cough, of Bronchitis. In larger
doses it produces first nausea, then vomiting.

Still more decided nausea is produced by Tartar Emetic. It is followed
by vomiting when the dose is sufficiently large. Nausea consists in a
sensation of discomfort about the præcordial region, which is due to a
derangement of the stomach, with a feeling of great languor, a cold
perspiration and tremor, and at the same time a striking depression of
the action of the heart. This nausea may be caused without vomiting, by
a regulation of the dose. On account of the depression of the heart's
action, which is its chief symptom, it is often very desirable to cause
nausea in acute inflammations and fevers. It is kept up by the careful
administration of Tartar Emetic. It may not be so desirable to produce
vomiting; for this is accompanied with great vascular excitement and
active congestion of the brain. And yet it is found that the more
Antimony we can get into the blood, the more potent and durable will its
antiphlogistic influence be. For this medicine appears to possess a
blood-action as well as an action on nerve. Experience has shown that if
the dose of Tartar Emetic be gradually increased on each repetition, it
may often be tolerated by the system; that is, it does not produce
vomiting; and then the remedy, being absorbed, is better able to
continue its antiphlogistic and nauseating action. For the act of
vomiting, besides other bad consequences, causes the rejection of that
part of the antimonial which has not been absorbed. By the operation of
the Nauseant the violent action of the heart in high fever may be
allayed. It is often of signal efficacy, most especially in Pneumonia.

Digitalis given in large doses may also act on the stomach, and cause
vomiting. This operation has been ascribed, erroneously, as I think, to
an irritating action possessed by this drug. But in smaller doses it
affects the heart and circulation powerfully, without producing the
other symptoms of nausea. It depresses the action of the heart.
Sometimes the rapidity of the beat is slightly increased at the first,
but the pulse at the same time is weaker. It soon becomes slower and
sometimes irregular. This action is characteristic of derangement of the
Vagus nerve. For it was found, in some experiments on animals made by M.
Weber, that when the function of this nerve was disturbed by mechanical
irritation, the rate of the heart was first accelerated, its action then
became slow and irregular,--and finally it stopped. There cannot be a
greater mistake than an attempt to explain such a derangement by
supposing this medicine to exert a primary stimulant action. Coincident
with the quickening of the pulse, there is a manifest loss of power.

Digitalis is especially useful in dropsies which result from an
obstruction to the cardiac circulation. By subduing the action of the
heart, it relieves that congestion of the vascular system which is the
cause of the effusion of serum. But it is also a Diuretic; and may thus
too relieve the loaded vessels by carrying off in the urine some of the
water of the blood.

Such is an outline of the action of Special Sedatives to the Vagus
nerve. It is not clear whether they affect that nerve at its origin in
the brain, or whether they act the extremities of its filaments.

These Sedatives do not act directly upon the brain itself. But
indirectly they may affect it, when given in large doses. For by
depressing the action of the heart they cut off the natural supply of
blood to the brain, and may, by so doing, produce delirium and
convulsions. They tend obviously to kill by syncope. Some medicines may
cause syncope by an action upon the brain. General Sedatives may do so;
but it does not appear that the medicines of this order ever act in this
way.

Some other medicines rest very closely upon the confines of this order.
Squill is the chief of these. It is not quite clear whether Squill
should be regarded as a Special Sedative, or considered simply as an
irritant Emetic and Eliminative. It is a valuable Expectorant. It is
also a Diuretic; and from the analogy of its operation to that of
Digitalis (_vide supra_,) and because it appears to be a specific
Emetic, it is most probably a true Neurotic.

But we must not confound with Neurotics those medicines which exert a
slow operation in the blood which results at length in a nervous
affection. This may take place, to a greater or less degree, with all
Catalytic Hæmatics. Lead, which is anti-convulsive and astringent,
approaches nearest of all to the recognised nerve-medicines. After
existing for some time in the blood, it produces local palsy,
particularly of the muscles about the wrist; and it sometimes affects
the sensory nerves, causing sharp shooting pains in the limbs. These
nervous symptoms are caused by the accumulation in the system of the
poison of lead, and the deterioration of the blood which is thereby
produced. In the case of the palsy, we cannot certainly say whether
these causes operate first upon the motor nerves, or upon the muscles
themselves.

Lead certainly has some tendency to affect the brain. All kinds of brain
disorders may occur in cases of chronic lead-poisoning. The metal has
been found in the brain after death; but it also exists at the same time
in other parts of the body. In cases of Lead-colic there is generally a
paralysis of the muscular fibre of a certain portion of the intestine.
The pain of the disorder is caused by an irritation of the nerves of the
part.

Neurotics are medicines which tend, immediately they enter the blood, to
be discharged from it upon the nervous system. They therefore
immediately affect the latter. Hæmatics, in small doses, pass through
the blood without exerting any direct effect upon the nerves. They are
never discharged upon the nervous system except after they have for some
time existed in the blood in such quantity as materially to vitiate its
healthy character. Corrosive poisons affect the nerves by a violent
revulsive action; and are not to be considered in the same category as
medicines. Thus Lead is not a true Neurotic, but a blood-medicine.
(_Vide_ page 175.)

We have now concluded our brief review of the action of Neurotic
medicines. Some few will be again treated of in the fourth chapter. The
views of their operation which I have wished to substantiate are in many
cases the same as those which are generally adopted, in some cases
different from them. In either instance I have attempted to base them on
observation, or on simple inductive reasoning.

It has already been observed that these nerve-medicines are more rapid
and more evanescent in their action than those which preceded them. They
are unable, as a general rule, to produce a permanent effect. When such
a permanent impression is desired, an approach to it can be made by a
continual repetition of the dose, by which a transitory action may be
constantly renewed and kept up. In other cases a mere transitory action
may produce a cure. This may be the case in a sudden and dangerous
emergency, which will pass over if the system can be supported through
it, but which threatens life while it lasts. Or in Neuralgia, if the
irritability of the sensory nerve be continually blunted by the external
application of Aconite, it may at last subside altogether, and a right
condition of things be restored. The same may be said of convulsive
disorders, and the stimulant antispasmodics which are used to control
them.

Neurotics are mostly employed in temporary emergencies. In such cases
their action is often decisive and gratifying. Vital action may be
restored and kept up; or excess of action allayed. Pain may be suddenly
and effectually removed; delirium or convulsions subdued. Sleep may be
substituted for wakefulness, or activity for torpor. By these powerful
remedies we are enabled to exert an immense control over the varied
manifestations of nervous force; and may often, when we wish it,
substitute one condition for another which is the reverse of it. When
there is a deficiency of nervous force, we make use of a Stimulant, or
of one of the Inebriant Narcotics; when there is an excess of the same,
we employ a Sedative, or one of the latter two Narcotic orders.

But when we desire to quell a long-standing and firmly-rooted disorder,
which is not displayed by violent outward manifestations, but is
nevertheless working fatally within, we must then call to our aid some
Hæmatic medicine, which alone can be of permanent efficacy in such a
case.

PROP. IX.--_That a third class of medicines, called_ ASTRINGENTS, _act
by passing from the blood to muscular fibre, which they excite to
contraction._

Although this class of Astringents is a small and comparatively
unimportant class, yet it is necessary to separate it from all the
others, because the medicines which compose it are completely distinct
in their mode of operation. They do not necessarily act in the blood,
although many Hæmatics are also astringent. They do not pass from the
blood to the nerves. They do not always act by passing out of the body
through the glands. Their operation is peculiar, but it is simple. As
Neurotics act directly on nerve, so these act directly and especially on
muscular fibre. They cause this to contract, whether it be striped and
voluntary, or of the involuntary unstriped kind.

Their action is more readily understood, because it can actually be
seen. It takes place out of the body, or in the body--externally, or
internally. Nearly all astringents have the power of coagulating or
precipitating albumen. By virtue of this power they are enabled to
constrict many dead animal matters. They affect fibrinous tissues in a
similar chemical way. But they seem to possess a further dynamical
influence over living tissues, which possibly depends in some way on
this chemical property. This dynamical influence is, as I have said, to
cause the contraction of muscular fibre. By this all their operations
can be explained. Taken into the blood in a state of solution, they pass
through the walls of the capillaries to the muscular tissue. By inducing
the fibre of the voluntary muscles to contract, Astringents may brace
the system, and simulate the action of Tonics. But as the contraction of
voluntary muscle is short and brief, it requires for its maintenance a
continual excitation, and unless the medicine is thus continually
repeated, the tonic effect subsides. But astringents further contract
involuntary muscle. This contraction is slower, and more durable and
important in its results. Unstriped muscular fibres exist in the middle
coat of arteries, in the walls of capillary vessels, in the lining of
the ducts of glands generally, and in the substance of the heart and the
coats of the stomach and intestines. Astringents are irritant and
poisonous in large doses. But in small doses they constrict and
stimulate to a healthy condition these tubes that contain in their coats
the unstriped fibre. By diminishing the caliber of the capillary vessels
generally, they promote health, and counteract a lax state of the
system. By the same action on the extreme vessels, they prevent
hæmorrhages. By constricting the ducts of the glands they diminish the
secretion of those glands, because denying it an exit. By acting on the
stomach and intestines, they are able to give them tone, to diminish
their secretions when excessive, and thus to promote digestion.

Having premised this general view of their action, we may now proceed to
prove the Proposition in which it is stated, dividing it first into four
minor propositions.

    _m. p. 1._--That they are medicines which pass into the blood.

    _m. p. 2._--That they have the power of causing the contraction
                      of muscular fibre, living or dead.

    _m. p. 3._--That their operation is to diminish secretion, to
                      repress hæmorrhage, and to give tone to the
                      muscular system.

    _m. p. 4._--That these results are to be accounted for by their
                      action on muscular fibre, to which they pass from
                      the blood.

These assertions are an extension of the major proposition, but their
establishment is necessary to a correct understanding of the latter.
Their proof is comparatively easy and simple. It is not supposed to be a
certainty; but simply to amount to a strong probability, which is as
much as we have a right to expect in such cases.

Astringents constitute the third class of medicines which operate on the
system after being introduced into the stomach. Their action is,
however, of so simple a kind, that it may be exerted on the external
surface in the same way as in the interior of the body. It will be seen
by a reference to the table of medicines, that the class of Astringents
is there divided into two orders.

    ASTRINGENTIA.

    Ord. 1. Astringentia Mineralia.
    Ord. 2. Astringentia Vegetabilia.

The lists of these orders are given below. With regard to the first
minor proposition, it has already been proved that most of these
medicines pass into the blood. The minerals included in the first order
have already been noticed as Hæmatic medicines. They are all soluble in
water. They are absorbed in the stomach and intestines, and pass into
the blood. Many of them pass on into the secretions. The astringent
parts of the vegetables of the second order are also soluble. Tannic
acid is the chief of them; it is simply an Astringent; it has been found
in the blood, where it changes into Gallic acid, and in that form it
passes into the secretion of urine.

What then are the active properties of these medicines? They have all a
certain chemical power; and a certain dynamical power. All the mineral
Astringents have the power of precipitating an albuminous solution. So
also do Tannic acid, Turpentine, and Creosote, coagulate albumen. Tannic
acid precipitates Gelatine too. The dynamical property, which is common
to all of these substances, is a power of causing the contraction of
muscular fibre. It seems to depend somehow on the chemical power just
mentioned; for Astringents appear to constringe fibrinous as well as
albuminous tissues by a chemical action. They also coagulate fluids and
discharges which contain albumen.

When the solution of any Astringent is applied to a fresh fibre of dead
muscle placed under the microscope, it is seen to contract. The power
which they possess in causing the contraction of living blood-vessels
may be witnessed in a similar way. The astringent solution may be
applied to the web of a frog's foot, confined in an extended position.
This web is traversed in all directions by minute ramifying capillaries;
and these are found gradually to diminish in caliber. In the same way as
the mechanical irritation of a small artery will act upon the unstriped
muscular fibre contained in its coat, and thus cause the vessel to
contract at one point; so it seems that an Astringent, by a chemical
action on the same muscular tissue, is able to cause the capillary
vessels seen under the microscope to contract and diminish in size. At
all events we may conclude, both from actual experiment and from a
comparison of their several operations, that Astringents are able to
cause the contraction of muscular fibre.

In the third minor proposition the chief results of their operation are
stated. These have already been briefly described.

They check secretion. They are thus prescribed when any secretion is
excessive. The Tannic vegetables are given in diarrh[oe]a; Nitrate of
Bismuth is administered in Pyrosis; Sulphuric acid in profuse
perspirations; Uvæ Ursi in mucous flux from the bladder.

They repress hæmorrhage. Thus Acetate of lead is employed in
hæmoptysis; Creosote and Uvæ Ursi are used in hæmorrhage from the
stomach or bladder; and the vegetable Astringents are prescribed in
Dysentery.

They give tone to the system. They do this when there exists an
over-relaxation of the solid fibres on account of any depressing cause,
by exciting the muscles to a more or less permanent contraction, and by
constringing the capillary vessels generally.

In the fourth place, it is maintained that their action in all these
instances may be explained by a reference to their power in causing the
contraction of muscular fibre; inasmuch as they are found to diminish
the caliber of certain tubes and cavities, and these owe the
contractility which they possess to the muscular fibre which is
contained in their coats. It follows then from the rule of local access,
that before they can influence these tissues they must pass directly to
them from the blood.

Such appears to be the simplest and the most rational explanation of the
action of Astringent medicines.

ORD. I. MINERAL ASTRINGENTS.

(Sulphuric, Nitric, and Hydrochloric acids. Acetate and Diacetate of
Lead; Sulphate and Sesquichloride of Iron; Alum; Sulphate of Zinc;
Sulphate of Copper; Bichloride of Mercury; Nitrate of Silver.)

These medicines have already been noticed among Restorative and
Catalytic Hæmatics. Their Astringent action on muscle is of much less
moment than their important operations in the blood. Neither is it
theoretically a matter of so much difficulty; for it appears, as we have
seen, to admit of a simple explanation.

By their chemical action on albumen, these substances coagulate blood,
and thus act in a simple way as styptics when applied to bleeding parts
externally. They form peculiar insoluble compounds both with albumen and
fibrine, and it is probably by virtue of their action on the latter
that they are able to cause the contraction of muscular fibre, which is
a fibrinous tissue. The constriction, set up chemically, is apparently
continued and propagated by the vital force of the muscle.

The most important only of the mineral Astringents are mentioned above.
It must not be supposed, when their chemical actions are mentioned, that
such actions are always allowed free play in the living and circulating
blood. They are no doubt constrained by various forces from operating
there, or else the consequences of such a disturbance of the condition
of the elements of the blood would be dangerous in the extreme. (_Vide_
page 104.) They act, before entry into the blood, on mucous membranes
and external parts; and on coming out of the blood, on the terminal
capillary vessels, on the ducts of glands, and on mucous membranes
again.

Astringents act very much alike on external parts; only that some are
more soluble than others, and some excel the rest in chemical activity.
But they differ considerably in their applicability for internal use.
They must be given in such quantity that, after absorption and dilution
by the whole mass of the blood, they may still be capable of exerting a
perceptible action on distant parts. A small portion of one of them will
not suffice to repress hæmorrhage, or to diminish a super-abundant
secretion.

From this it follows that the mineral acids, Alum, and the salts of
Iron, are the only astringents of this order which can in all cases be
given internally with advantage. For being comparatively innocuous, they
can be safely prescribed in the quantity required; whereas the other
mineral Astringents are poisonous substances, which cannot be given in
large doses without considerable danger.

Of the mineral acids, Sulphuric acid is the best Astringent. Phosphoric
acid is seldom or never used as an Astringent. We might indeed have
supposed it to be inapplicable, from the fact that it forms soluble
compounds with albumen and fibrine,--instead of coagulating these
substances, like the other mineral acids.

Sulphuric acid is a Restorative Hæmatic; and, when given in small doses,
may remain in the blood, and not pass out through the glands. It acts
first upon the mucous surface of the stomach. When there is a relaxation
of this mucous membrane, as in many cases of atonic dyspepsia, with a
large formation of flatus, and an over-secretion of the gastric fluid,
this acid may be very serviceable. It tends to correct these evils by a
topical action. In cases of Pyrosis, where there is an alkaline reaction
in the vomited fluid, as sometimes occurs, Sulphuric acid is still more
peculiarly applicable, because it further acts chemically in
neutralizing this alkali. When given in large doses, the acid cannot
remain in the system, but must be excreted from it by the glands. In
passing through them it tends to act as an Astringent by corrugating and
diminishing in caliber their minute ducts, and thus decreases the amount
of the secretion. But it does not act on all glands alike. Dr. Bence
Jones has found that it seldom passes out into the urine. It therefore
does not sensibly diminish the secretion of urine. It is probably
excreted partly by the skin, and partly by the bowels; for it diminishes
the amount of the sweat in profuse perspiration, and of the fæces in
diarrh[oe]a. Sulphuric acid is free before entrance into the blood, and
after expulsion from it into the secretions. Thus at these periods it
acts as an Astringent. But while in the blood it combines with the
alkali contained in that fluid, and forms a salt which is not
astringent. So that when it diminishes any secretion, this is nearly
tantamount to a proof that it is actually excreted by the gland which
forms that secretion. It acts on mucous membranes generally, being
probably excreted in small quantities by those which are remote from the
stomach. It is not of use in cases of hæmorrhage, except when the
bleeding takes place from some mucous membrane. It is thus given with
more or less advantage in Hæmatemesis, Hæmoptysis, Melæna, and chronic
Dysentery--_i.e._ in hæmorrhage from the mucous surfaces of the lungs,
stomach, and bowels.

Alum is a universal Astringent, acting more or less on all parts of the
body, and diminishing all secretions. It is a very useful remedy in all
cases where Astringents are required. It does not seem to be impaired in
power while in the blood, as is the case with Sulphuric acid; and is
therefore applicable in all hæmorrhagic cases. It has been highly
recommended in the case of lead colic, and seems to operate in this
instance by stimulating to contraction the muscular fibre of a paralyzed
portion of the intestine.

The astringent salts of Iron are less active in this kind of influence
than the medicines already referred to. They have very little action on
the glands. But in cases of hæmorrhage they are particularly
appropriate, for in addition to their astringent action they tend to
restore the deficient red colouring matter of the blood. In many such
instances the Sulphate or the Sesquichloride of Iron may be
advantageously prescribed along with Sulphuric acid.

Acetate of Lead is used internally as an Astringent, but being a more
dangerous remedy than the medicines above mentioned, it requires greater
care in its application. It should not, if possible, be used long at a
time. When it has been for some time prescribed, the blue line at the
edge of the gums, which is characteristic of a saturation of the system
by the poison of lead, will indicate that its further administration is
unadvisable. The Acetate of Lead is much esteemed as an Astringent in
the case of Hæmoptysis. It is frequently combined with Opium, in spite
of the chemical decomposition which follows the admixture. But it must
certainly not be prescribed with Alum.

The soluble salts of Silver, Zinc, and Copper, and the Bichloride of
Mercury, are used with advantage as external Astringents, but can seldom
be prescribed internally so as to act in this way, because they are
poisonous when given in any quantity. The Sulphates of Zinc and Copper
have, however, been occasionally used in diarrh[oe]a.

When thus applied as Astringents externally, their solutions must be
very dilute, for all the mineral Astringents are caustic and corrosive,
destroying texture, when in the solid state, or in strong solutions.
These solutions may be applied to any part of the surface of the skin or
mucous membrane, when relaxed, inflamed, or ulcerated. Their operation
is simple and obvious. When one of them is applied to an inflamed eye,
or to a red ulcerated sore, that is turgid with blood and discharges an
unhealthy matter, it tends to promote the contraction of the dilated
vessels, and thus dispels the congestion and diminishes the discharge.

Various other substances have wrongly obtained the title of Astringents,
regard being had only to the result of their operation, and not to the
mode in which it is produced. Thus Chalk is often of benefit in
diarrh[oe]a. It acts both by mechanically absorbing irritating fluids,
and protecting the surface of the bowel, and by chemically neutralizing
an acid matter by which the irritation is maintained. And when applied
to the surface of inflamed ulcerated parts, it does good by absorbing
the discharge, and protecting from the contact of air. Thus its action
in both cases is very different from that of the true Astringents.

The action of some of the minerals above named, when applied externally
in the solid state, as caustics, must not be confounded with their
astringent power. Its efficacy depends upon the revulsive effect which
follows a local destruction of tissue.

ORD. II. VEGETABLE ASTRINGENTS.

(Tannic Acid. Gallic Acid. Kino; Catechu; Logwood; Oak-galls; Rhatany;
Bistort; Pomegranate-rind; Rose-leaves; Uvæ Ursi; Tormentil. Creosote.)

Tannic Acid, Gallic Acid, and Creosote are the three chief Vegetable
Astringents. To the first two the vegetable substances above enumerated
appear to owe their efficacy. All contain Tannic Acid, or some
modification of it; and Oak-galls contain also Gallic Acid.

The relative efficacy of these active principles may be summed up in a
few words. Tannic and Gallic Acids may generally be used with great
advantage in all cases in which Astringents are required. When applied
externally, Tannic Acid is the most powerful; but for internal
administration Gallic Acid is the best. The reason of this will
presently appear. Creosote, being a powerful Neurotic, cannot be
employed to act on distant parts, but is appropriate in cases of
hæmorrhage from the surface of the stomach.

I have already said that I conceive the astringent powers of these
substances to depend very much upon their chemical affinities. Tannic
Acid precipitates both Albumen and Gelatine. Creosote also coagulates
Albumen. But Gallic Acid does not affect either of them.

Tannic Acid does not seem to be a simple substance. When boiled with
acids, or with alkalies, it yields Gallic Acid and a brown matter.
Tannic and Gallic Acids yield the same set of products when submitted to
destructive distillation. And it appears likely, from the researches of
M. Braconnot, that Tannic is a compound acid consisting of Gallic Acid
in combination with the elements of grape-sugar. Three atoms of Tannic
Acid are together equivalent to six atoms of Gallic Acid and one of
grape-sugar. When the solution of the former acid is heated in the air,
or taken into the human system, the elements of grape-sugar are
oxidized into Carbonic Acid and water, and Gallic Acid is set free.
(_Vide_ Chap. IV. _Art. Tannic Acid_.)

It is thus Gallic Acid which passes out into the secretions, and exerts
an astringent action at distant parts of the system. And as the Tannic
Acid loses weight by the decomposition, it follows that a dose of Gallic
Acid produces a greater effect as a medicine than an equal amount of the
other. Thus one ascertained fact is cleared up by these chemical
considerations, but other mysterious points remain still to be
explained.

Gallic Acid does not precipitate albumen, and is of little use as an
Astringent when applied to external parts; but it is very efficacious
when given internally. Tannic Acid, which is equivalent in composition
to a combination of Gallic Acid with a saccharine matter, is a valuable
external Astringent. A further chemical discovery has been made, which
appears to bear upon these facts. M. Pelletier has found that a mixture
of a solution of Gallic Acid with one of Gum will precipitate albumen,
although neither of them will affect it separately.[43]

Gum has the same composition as common sugar; and grape-sugar, or a
material containing the same elements, is known to be continually
forming in the blood. Thus it is likely that Gallic Acid may act along
with this saccharine matter in the blood, and by this acquire chemically
an astringent power, which it is not able to exert on external parts,
because then isolated. But the saccharine matter is required in the
system for special purposes, and thus Gallic Acid passes out into the
secretions alone.

It seems probable, when Tannic Acid is given, that it is not decomposed
into its constituent parts until it has to be separated from the blood
by the glands.

These two compounds, and the vegetable substances that contain them, are
used in diarrh[oe]a, and in all hæmorrhagic cases. To diminish
sweating, Tannic is inferior to Sulphuric Acid; but to act as a remote
Styptic, it is preferable to the other. Tannic and Gallic Acids diminish
secretions generally; they are very useful in cases of hæmaturia, where
Sulphuric Acid is all but useless.

Creosote is a Sedative, and cannot be well given in such large doses as
to act upon distant parts. In cases of hæmatemesis it acts topically on
the surface of the stomach in a double way, diminishing the hæmorrhage
by its astringent power over the vessels, and quieting the nervous
irritation by which the vascular excitement is often maintained. In
cancerous cases the bleeding can never be permanently stopped.

This concludes the list of Astringent medicines.

Certain stimulant Eliminatives are employed for the purpose of checking
mucous fluxes, and so far simulate the action of true Astringent
medicines. Thus we administer, with more or less advantage, Aromatics in
diarrh[oe]a; Cubebs, Copaiba, and Turpentine, in gonorrh[oe]a; and
Balsam of Peru, and other oleo-resins, in Catarrhal affections. These
medicines all act upon and pass through the glands of the several mucous
surfaces which they affect: while so doing, they stimulate the healthy
function and secretion of the gland, and cause it to displace the morbid
one. Dr. Williams thinks that they first cause dilatation of the vessels
of a gland, and that this is followed by contraction. There is no
apparent reason why the latter effect should succeed the former. But
supposing contraction to take place in this way, then these medicines
would be true Astringents. But it cannot be so, for they do not diminish
any of the natural secretions, but, on the contrary, increase them.
Turpentine, Cubebs, and Copaiba, are Diuretics, and it is possible that
while passing out in the urine they may simply stimulate the mucous
surface of the inflamed urethra, and excite it to a healthy action.

These volatile oils are incapable of exerting a true astringent action.
On the supposition that it is really an Astringent, Turpentine has been
often prescribed as a remedy for hæmorrhages in different parts of the
body. But it has very much disappointed the expectations that were
entertained of its efficacy.

General Stimulants may act indirectly as styptics to a mucous surface,
when relaxed and bleeding on account of an atonic condition of the
nerves by which the contraction of the minute vessels is maintained.

Alcohol, in large quantity, coagulates albumen, and it may thus act as a
true Astringent when applied externally.

Some Neurotic medicines diminish secretions in a way which is not well
understood. The chief of these is Opium, which particularly diminishes
the secretion of the bowels. Attempts have been made to explain this by
an influence possessed by Morphia on the process of Endosmosis, but they
are not satisfactory. Some little light may perhaps be thrown upon the
matter by a consideration of the other operations of Opium; but it is
difficult to explain it decisively in any way.

PROP. X.--_That a fourth class of medicines, called_ ELIMINATIVES, _act
by passing out of the blood through the glands, which they excite to the
performance of their functions_.

In this Fourth Class are included all the medicines which tend in a
direct manner to increase secretion. They have received various
appellations: some authors have called them special Stimulants; others,
as Dr. Duncan, have named them Evacuants; while Dr. Pereira entitles
them Eccritics.

The mode of operation of Eliminative medicines is a matter of
considerable importance, and its consideration will require us first to
make some inquiry into the character and functions of those important
glandular organs which they are said to excite to action.

The rational explanation of the process of elimination or secretion has
been in all ages of science a favourite topic for speculators and
theorists,--sound or unsound in their views, according to the light that
was given to them. With regard to its essential nature, and its
immediate bearing on the cure of disease, the subject has been generally
understood with tolerable clearness. From the time of Hippocrates
downwards, the use of Evacuants in the treatment of fevers and other
disorders has been recognised, and their efficacy usually explained by
supposing that they caused the passage out of the body through the
glands of certain matters that were formed in the blood, but ought not
to remain in it.

This view was more particularly insisted on towards the close of the
seventeenth century by Dr. Thomas Sydenham; and again at the
commencement of the eighteenth by Dr. A. Pitcairn, in an Essay on the
use of Evacuants in Fevers. These both had observed that fevers and
other disorders had mostly a particular tendency to pass off with an
increase in one or more of the secretions; and they drew from this, and
from the results of their experience, that in stimulating and urging
this secretion, the physician would be doing his best to promote a cure.
(_Vide_ page 55.) More recently the same idea has been followed up by
Cullen, Hamilton, and others.

This theory is not in our immediate province. Though based upon
reasonable grounds, it has perhaps been too universally applied. It will
suffice now if we assume that remedies whose action is to increase the
amount of secretion have often an important bearing on the cure of
disease. We have only to inquire into their manner of action. As a
preliminary step, there is one general law of secretion which it is of
importance that we should clearly lay down. It is this: it is the
special office of each gland, or set of glands, to secrete from the
blood particular materials, and to pass them out of the body.[44]

It follows from this law of selective secretion, that when any morbid
substance or product,--or any thing which is in the system, but cannot
naturally remain there,--has to pass out, it prefers to pass by some
glands rather than by others. It must be remembered that the glands
afford the only means by which a substance can make its exit from the
blood. We are still much in the dark as to the _rationale_ of this force
or attraction, by which particular matters are drawn towards each gland.

Dr. Pitcairn, a great man for the age in which he lived,--a man of
original thought and natural genius,--gives us, in his Essay on the
Circulation of the Blood, a learned account of three theories on this
matter which were in vogue at his time. They are of importance, as
showing that the fact was then very clearly recognised, however dubious
the explanation of it might be. One party supposed that there was in
each gland a certain material stored up, which prevented the passage
through to itself of any substance that was not like it; just as when a
sheet of paper is steeped in oil, oil only will pass through it, and not
water. A second party, called the Chymical party, supposed that there
must be in the immediate neighbourhood of each gland a subtle fluid or
ferment, whose tendency and office it was to form and separate from the
blood the materials which that gland had to secrete. A third set of
physicians armed themselves with mathematics and with the newly
discovered principles of Newton, and actually worked out formulæ and
equations wherewith to support their arguments. They had strong and
perhaps reasonable ideas as to the definite shapes of atoms. They
averred that each gland was to be compared to a sieve or strainer,
having in it pores of a particular size and certain geometrical shape,
and that each secreted atom could only pass through a pore that would
exactly coincide in size and figure with itself.

The first two of these theories Dr. Pitcairn disputed, and treated with
high disdain. The third he accepted in a modified form. He supposed that
the vessels in the glands ended in small open mouths, always circular,
but differing in diameter in different glands, so that each would only
admit the passage of a particle whose diameter approached a certain sum.
Thus he supposed that each secretion would consist only of certain
peculiar particles. Possibly Dr. Pitcairn forgot that small particles
would seldom hesitate to pass through large holes.

We may perhaps feel inclined to make light of these crude speculations
of the philosophers of the eighteenth century; we may be disposed to
smile at the idea of vessels with open mouths, and of glands which are
riddled with holes like the buckets of the Naiades; but we must after
all confess that if at the present day we have swept away these notions,
we have certainly added nothing in their stead, nor can we explain this
matter at all more clearly than our predecessors a century and a half
ago.

The fact, however, is plain, however vainly we may try to explain it. It
is an established rule, to which there are few exceptions, that each
substance which is formed in the blood and has to pass out of the body,
tends to pass out through some particular glands; that it is the
particular function of the kidneys to excrete water, urea, uric acid,
and certain salts; that it is the especial office of the bowels to
excrete certain effete matters and gases; and that it is the peculiar
province of the liver to excrete fatty matters, taurine, cholesterine,
and choleate of soda.

Water, being the necessary solvent of the solid matters in all the fluid
secretions, is secreted in greater or less quantity by all the important
glands. The kidneys are the chief emunctories of water,--_i.e._ they
have to separate it from the blood when it has entered in an unnatural
amount. But in the excretion of water there exists a compensating
relation between the skin, kidneys, and bowels,--particularly between
the two former. So that when water is not properly excreted by the
kidneys, it may pass out by the skin, and _vice versâ_. It is well known
that this change may be determined by several circumstances,
particularly by the conditions of heat and cold, or moisture and
dryness. The relation between the function of the skin and kidneys
applies also to other fluid and solid substances, as will be seen when
we consider the medicines which act upon these glands.

Now this law of selective secretion applies not only, as it seems to me,
to substances which in the course of nature are formed in the blood, and
have to be excreted from it, but also to other matters which have been,
as it were, accidentally introduced from without, and which, being in
the system, cannot properly remain there. Thus it would apply to all
medicinal bodies which have passed from the stomach into the blood, and
which, not being natural constituents of that fluid, must again pass out
of it.

So that although it is often laid down that medicines acting on the
glands do so simply by passing along in the blood, and stimulating them
as they go by, I regard this as a needless complication of the subject,
and a thing which is wholly without proof. In fine, I am brought to the
opinion which I have laid down in the Tenth Proposition, and which I
have now to establish as well as my space will permit. The affirmation
may be thus divided into minor propositions:--

    _m. p._ 1.--That Eliminatives are medicines which pass into the
                      blood.

    _m. p._ 2.--That they cannot remain there, but must pass out
                      of the body.

    _m. p._ 3.--That in so doing, they tend to pass out by some
                      glands more than by others.

    _m. p._ 4.--That the result of their passage through a gland is
                      to increase its secretion.

    _m. p._ 5.--That they are of use when the state of the system
                      requires that the function of a gland should be
                      restored or promoted.

What I wish to prove is, that a medicine increases secretion simply by
being itself secreted; that while passing through a gland it stimulates
the secreting cells, and rouses them to a proper performance of their
natural function; that each eliminative medicine has a tendency towards
particular glands, and increases the secretion of those glands; that
thus, as far as our information on the subject extends, we find that
Cathartics are excreted from the blood by the glands of the bowels, and
pass out with the fæces; that Diuretics are to be discovered in the
urine, Diaphoretics in the sweat, and those Expectorants which are
volatile may be detected in the odour of the breath.

Any material which is naturally eliminated would act as an eliminative
medicine. Thus if a drachm of Urea be dissolved in water, and injected
into the veins of a dog, it causes copious urination, which continues
until the whole is excreted. This well illustrates the argument.

Further, we find that when an eliminative medicine is diverted from the
gland by which it usually passes out, it no longer augments the
secretion of that gland. Dr. Ward gives an interesting case of a woman
who was never purged by Castor-oil, but in whom the oil exuded from the
skin, and acted as a Diaphoretic. And it is, as I have said, well known
that the conditions of cold and exercise will cause a Diaphoretic, in
most cases, to act on the kidneys, because it is then excreted by them.
For the same reason, warmth, confinement, and rest, will induce a
Diuretic medicine to act on the skin.

Thus if it be shown, on the one hand, that Eliminative medicines
themselves pass through the glands whose secretions they augment; and,
on the other hand, that when they do not pass through them, they do not,
as a general rule, augment their secretion,--it may then fairly be
presumed that they operate by so passing through.

I assert, then, that medicines which stimulate secretions are themselves
secreted. But the converse of this--_i.e._ that all medicines which are
secreted at the same time increase secretion,--though it holds good in
the main, is not invariably true. There are two chief exceptions to it.
These are Astringents and Hyperæmics.

When an Astringent passes through a gland, it tends, by its natural
force, to decrease secretion, and to cause constriction of the ducts.
Thus Uvæ Ursi may decrease the amount of the urine, although it
sometimes does the opposite; in which case the eliminative may be said
to surmount the astringent tendency. So also Catechu, Kino, and
Sulphuric Acid, decrease the secretion of the intestinal glands. But
general Astringents are not always glandular Astringents. Thus the
mineral acids act as Diuretics.

By Hyperæmics I mean medicines which produce congestion. Powerful
Eliminatives do this when given in excess, simply by exciting excessive
action. Now it is a general rule that congestion, however caused,
diminishes the secretion of a gland. Thus congestion of the liver
produces jaundice; congestion of the kidney, ischuria. After scarlatina,
when the kidneys are suddenly called upon to eliminate a morbid material
from the blood, congestion of the glands may be caused: the urine is
diminished, and dropsy results.

Cantharides and Turpentine are Diuretics. They increase the urine when
taken in moderate doses; but when in an overdose, they diminish it, and
may cause painful strangury, with an almost total suppression of the
secretion. The explanation of such an action is obvious. Congestion is
caused by the excessive action. In the same way we find that a large
dose of Mercury, naturally a Cholagogue, may produce jaundice, by
causing congestion of the liver. This fact has been observed by Dr.
Graves, of Dublin.

In all cases, then, in which observations have been made, we find that
an Eliminative medicine is secreted by the gland which is stimulated by
it, and, in most cases, that a medicine which is excreted by a gland
tends to increase its particular secretion.

Having made this general statement of the case, I must attempt a more
particular and detailed proof. I will treat in turn of the above minor
propositions, as applicable to the following orders of Eliminative
medicines:--

    CLASS IV. ELIMINANTIA.

     Ord. 1. Sialagoga.
     Ord. 2. Expectorantia.
     Ord. 3. Cathartica.
     Ord. 4. Cholagoga.
     Ord. 5. Diaphoretica.
     Ord. 6. Diuretica.

They are enumerated nearly in the order of the glands, from above
downwards, in the human body. I have not enumerated Errhines, because
the medicines which are used to increase the nasal mucus are merely
topical irritants, and not true Eliminatives.

Of Emetics I have already spoken. Some are Neurotics, acting from the
blood on the nervous system; other are local irritants. They also are
not true Eliminatives.

Neither are Emmenagogues so; for the uterus is not a gland. Some of
these too are Neurotics. Most of them act by causing a determination of
blood towards the organ. Cathartics do this by their action on the
contiguous mucous membrane of the intestines. (_Vide_ page 102.)

These then are the six orders of Eliminative medicines. In the first
minor proposition it is stated that they pass into the blood. This has
already been in great part proved; for most Eliminative medicines belong
also to one or more of the preceding classes, of which it has been shown
that they pass into the blood.

Thus Antimony, Mercury, Acids, Alkalies, Sulphur, the Salts, etc., are
Hæmatics primarily. The various volatile oils and resins are more or
less Stimulants. So also Alcohol and Ether, as well as Camphor and
others, are found among Narcotics. Colchicum, Digitalis, Creosote, and
Ipecacuanha, are Sedatives. Many Eliminatives are certainly known to
pass into the blood, because they are subsequently found in the
secretions, as will be presently seen.

Secondly, these medicines cannot remain in the blood, but must sooner or
later leave it. If they remained, they could not pass through the
glandular cells. But if they pass out, they must inevitably be excreted
by them.

All those medicines must be secreted which have nothing in the natural
blood corresponding to them. This is the case with most Eliminatives,
and with all medicines except the Restorative Hæmatics. And those
Restoratives which act as Eliminatives, such as Acids and Alkalies, do
so because they are introduced in so large a quantity that they cannot
possibly remain in healthy blood. Thus all these medicines pass out
through the glands.

Thirdly, we find that in so doing they tend to pass out by some
particular glands rather than by others.

In order to show this we may consider first the chief tendencies of the
great groups of Eliminative medicines; and secondly, I shall endeavour,
when considering the six orders, to show that many of the medicines
included in them have actually been found in the secretions of the
glands towards which they tend. The first consideration will clear the
way for the second. What we have to ascertain is, that the principle of
selective secretion is generally applicable to Eliminative remedies.

The most important of the substances which are used to increase
secretion may be divided chemically under the following six heads, of
all of which it has been proved that they are capable of absorption.
(Prop. II.)

    1. Insoluble mineral substances.
    2. Soluble minerals,--_i.e._ Acids, Alkalies, and Salts.
    3. Ammonia and volatile oils.
    4. Fixed acrid oils.
    5. Resins and neutral acrid principles.
    6. Soluble vegetable principles.

1. _Insoluble mineral substances._--The chief of these are Mercurials
(Blue Pill and Calomel,) Iodine, and Sulphur. They are all more or less
changed during the process of absorption, as they have to be reduced to
a soluble condition. They stimulate secretion generally; but Mercury
particularly tends to the liver, bowels, salivary glands, and skin;
Iodine, to the kidneys, and to the salivary and mucous glands; Sulphur,
to the skin.

2. _Soluble mineral substances._--Acids, Alkalies, and Salts, may pass
off by any of the fluid secretions. The chief of these secretions are
the sweat, the urine, and the secretion of the bowels. The sweat is only
fluid when the skin is kept covered and very warm. In other cases the
choice lies between the kidneys and the bowels. The kidneys are the
grand purifiers of the blood, so that most of the substances which
stimulate the other glands may occasionally pass off in the urine. And
soluble minerals, which require some amount of water for proper
solution, would tend for this reason towards the most fluid of the
secretions.

But there are some other things which counter-balance this tendency.
The constitution of the urine is such that it cannot safely be disturbed
to a very great extent. If there be much excess in it either of acid or
of alkali, a deposit is occasioned. Dr. Bence Jones found that Sulphuric
acid never passed out in the urine in any quantity. We find too that
when a certain quantity of a saline is administered, too great to pass
off readily by the kidneys, it prefers to act on the bowels. It is more
likely to be diuretic if much diluted with water; but this is not the
only directing cause, for a very large quantity of a saline will prove
purgative even when largely diluted. (_Vide_ Prop. II.) Thus the general
rule is this: soluble minerals are in small doses Diuretic, in large
quantity Purgative. This applies more especially to salts; for mineral
acids act as astringents on the bowels,--and mineral alkalies, being
corrosive, cannot be given in large doses.

3. _Ammonia and volatile oil._--The laws of endosmosis favour the
passage of soluble substances through to a liquid secretion. They are
dissolved and carried away on the other side of the membrane through
which they pass. In the same way it appears that volatile substances may
dissolve in, and be carried away by, air. Thus they have a tendency
towards the aeriform secretions. These are,--the expired air, or the
secretion of the air-cells of the lungs,--and the ordinary cutaneous
transpiration. While passing through the air-cells, these matters
stimulate the secretion of the lining mucous membrane. They cause a
morbid secretion of this surface to be replaced by a more natural one.
Thus Ammonia and volatile oils are Expectorant and Diaphoretic. They may
all pass out in the urine, but do not especially tend to do so, with the
exception of some that are acrid, and approach to the nature of the
resinous group. Turpentine, Juniper, and Copaiba, are Diuretic.

4. _Acrid fixed oils._--Such are Castor and Croton Oils; they are
Purgatives, passing off by the bowels.

5. _Resinous and neutral acrid principles._--These are soluble in
alkalies, and thus partly absorbed in the intestinal canal. Most of them
are Cathartic, whether introduced into the stomach or injected into the
veins. Such are the resins of Scammony, Jalap, and Gamboge, and the
principles of Colocynth and Elaterium. Some few of them are Diaphoretic,
as Guaiacum and Mezereon. Some again are Diuretic, especially those
which are liquid or associated with a volatile oil, which is the case
with Copaiba, Cubebs, Cantharides, and others.

6. _Vegetable principles soluble in water._--Most of these are Diuretic;
as are the Vegetable Acids, and the Alkaloids of Digitalis, Tobacco, and
Colchicum. So also are the principles of Broom and Sarsaparilla. The
Emetine in Ipecacuanha, and the Morphia in Opium, act on the skin.
Aloesin, the principle of Aloes, is purgative. So is Cathartin, the
soluble acrid principle of Senna.

Having thus briefly sketched out the particular tendencies in the
operation of the groups of medicines which act on the glands, it remains
for me to say that in very many cases these medicines have actually been
proved to pass out of the body by the glands whose secretions they tend
to increase. Whenever we are in a position to inquire into the facts by
chemical or other means, we find that the Eliminative medicine is itself
contained in the secretion which is augmented by its action, and that
when the secretion upon which it usually acts is not augmented, the
medicine has passed off by some other secretion instead. There are
doubtless many cases in which no inquiry of the kind has been yet made;
but it will be seen when we consider separately the Eliminative orders,
that all that is known on the subject is in favour of the above
statement.

Assuming, then, the third and fourth minor propositions together, we
conclude that Eliminative medicines, which must pass out of the blood,
tend to pass out by some glands more than by others, and that the
result of their passage through a gland is to increase its secretion.

They do not exert a blood-influence, nor do they act on the nervous
functions; but they operate on those obscure vital forces by which
secretion is directed and controlled.

The fifth minor proposition treats of the application of these agents in
the treatment of disease. They are of use when it is requisite that the
function of a gland should be restored or promoted. There is scarcely
any disease in which some or other of them may not be of service. Their
remedial applications are many and important.

Eliminatives are used to restore the function of a gland when impaired.
With this view, Cathartics are employed in constipation, Diaphoretics
for dryness of skin, Cholagogues in torpid states of the liver.

They may eliminate a poison or morbid material, and thus resolve a
disease. This probably is the rational explanation of the use of
Diaphoretics and Diuretics in Fevers, Gout, and Rheumatism, and of
purgative medicines in a great number of disorders.

We may, by an action on one gland, be enabled to replace the function of
another gland. The amount of each secretion bears more or less an
inverse proportion to that of other secretions. Thus when one of them is
unduly copious, we may diminish it by stimulating the formation of
another. In other cases the reverse condition may occur; one of the
secretions may be diminished or suppressed by a cause over which we have
no control, and the matters which should be contained in it may be left
in the blood, causing various mischief there. Here again, by increasing
one of the other secretions, we may replace the function of the diseased
gland, and cause the elimination of these products from the body by
another channel.

Fourthly, Eliminative medicines may be of service by draining away from
the blood fluid and solid matters. The first result of their action is
to stimulate the proper secretion of a gland; but when it is pushed to a
further extent, they may actually case the excretion of some of the
natural constituents of the blood. Thus by an action on the skin or the
kidneys, we may cause a copious evacuation of water, holding in solution
saline matters. By increasing the secretion of the intestinal glands, we
may cause the albuminous serum of the blood to be poured out into the
cavity of the bowels. Thus it is that all Eliminatives are more or less
antiphlogistic. Cathartics are especially so. Their influence, when
carried to excess, is analogous to that of blood-letting. As evacuants,
Cathartics are employed in diseases of the brain especially; and
Diuretics are made use of in dropsies to diminish the amount of fluid in
the blood, and in this way to promote absorption.

So much having been said of the general action of Eliminatives, we
proceed to make a few remarks on the individual orders of medicines
which are included in this division. Those substances can alone be
properly included in these groups which really act on the principle of
elimination, as above defined. There are in many instances other
medicines which are found to increase secretion in an indirect way.

ORD I. SIALAGOGUES.[45]

This name is applied to medicines which in various ways increase the
quantity or promote the excretion of the saliva. They are seldom
employed as remedial agents; for the excretion of saliva is constant and
very rarely suppressed, and it is so small in quantity, and so great a
source of inconvenience when increased to any amount, that Sialagogues
can never be employed as general evacuants. There are two kinds of
Sialagogues.

Any solid substance which excites the mucous surface of the mouth, as
the natural food,--or even the act of mastication alone,--will suffice
to bring on the secretion of saliva. An irritant substance, as Ginger,
or Pyrethrum, tends especially to cause this secretion when masticated.
Catechu and Betelleaf are chewed for this purpose by the natives of the
East.

Such a stimulation of the salivary glands may be advantageously resorted
to on the counter-irritant principle in obstinate cases of head-ache,
ear-ache, or tooth-ache, or in neuralgic or chronic rheumatic affections
of the face.

When the quantity of the saliva is thus increased, it should not be
rejected, but always swallowed when possible; for this secretion is
apparently useful in the stomach, and in some way essential to the
proper carrying on of the digestive process. The chewing of Tobacco,
Betel, and other substances, is frequently found useful by sailors on
long voyages, and is adopted as a preservative against the dysentery and
diarrh[oe]a with which they are so often affected. This advantage is to
be attributed to the increase in the salivary secretion. On the other
hand, we find that the practice of constant spitting is productive of
very injurious effects; and it is more than possible that the pale
faces, lank figures, and dyspeptic maladies, which are so common among
the American people, may be due in part to the prevalence of this habit
among them.

These topical irritants and masticatories are not true Eliminatives.
There are also some medicines which by another topical action may
occasionally produce salivation. These are Sedatives. Hydrocyanic acid,
Digitalis, and nauseant medicines, may act locally so as to paralyze the
muscular fibres by which the constriction of the salivary ducts is
maintained, and thus allow the secretion to pour out uncontrolled into
the cavity of the mouth.