the 18th century A.D. (_Revue biblique_, July 1905).

EXOGAMY (Gr. [Greek: exô], outside; and [Greek: gamos], marriage), the
term proposed by J.F. McLennan for the custom compelling marriage "out
of the tribe" (or rather "out of the totem"); its converse is endogamy
(q.v.). McLennan would find an explanation of exogamy in the prevalence
of female infanticide, which, "rendering women scarce, led at once to
polyandry within the tribe, and the capturing of women from without."
Infanticide of girls is, and no doubt ever has been, a very common
practice among savages, and for obvious reasons. Among tribes in a
primitive stage of social organization girl-children must always have
been a hindrance and a source of weakness. They had to be fed and yet
they could not take part in the hunt for food, and they offered a
temptation to neighbouring tribes. Infanticide, however, is not proved
to have been so universal as McLennan suggests, and it is more probable
that the reason of exogamy is really to be found in that primitive
social system which made the "captured" woman the only wife in the
modern sense of the term. In the beginnings of human society children
were related only to their mother; and the women of a tribe were common
property. Thus no man might appropriate any female or attempt to
maintain proprietary rights over her. With women of other tribes it
would be different, and a warrior who captured a woman would doubtless
pass unchallenged in his claim to possess her absolutely. Infanticide,
the evil physical effects of "in-and-in" breeding, the natural strength
of the impulse to possess on the man's part, and the greater feeling of
security and a tendency to family life and affections on the woman's,
would combine to make exogamy increase and marriages within the tribe
decrease. A natural impulse would in a few generations tend to become a
law or a custom, the violation of which would be looked on with horror.
Physical capture, too, as soon as increasing civilization and tribal
intercommunication removed the necessity for violence, became symbolic
of the more permanent and individual relations of the sexes. An
additional explanation of the prevalence of exogamy may be found in the
natural tendency of exogamous tribes to increase in numbers and strength
at the expense of those communities which moved towards decadence by
in-breeding. Thus tradition would harden into a prejudice, strong as a
principle of religion, and exogamy would become the inviolable custom it
is found to be among many races. In Australia, Sir G. Grey writes: "One
of the most remarkable facts connected with the natives is that they are
divided into certain great families, all the members of which bear the
same name ... these family names are common over a great portion of the
continent and a man cannot marry a woman of his own family name." In
eastern Africa, Sir R. Burton says: "The Somal will not marry one of the
same, or even of a consanguineous family," and the Bakalahari have the
same rule. Paul B. du Chaillu found exogamy the rule and blood marriages
regarded as an abomination throughout western Equatorial Africa. In
India the Khasias, Juangs, Waralis, Otaons, Hos and other tribes are
strictly exogamous. The Kalmucks are divided into hordes, and no man may
marry a woman of the same horde. Circassians and Samoyedes have similar
rules. The Ostiaks regard endogamy (marriage within the clan) as a
crime, as do the Yakuts of Siberia. Among the Indians of America severe
rules prescribing exogamy prevail. The Tsimsheean Indians of British
Columbia are divided into tribes and totems, or "crests which are
common to all the tribes," says one writer. "The crests are the whale,
the porpoise, the eagle, the coon, the wolf and the frog.... The
relationship existing between persons of the same crest is nearer than
that between members of the same tribe.... Members of the same tribe may
marry, but those of the same crest are not allowed to under any
circumstances; that is, a whale may not marry a whale, but a whale may
marry a frog, &c." The Thlinkeets, the Mayas of Yucatan and the Indians
of Guiana are exogamous, observing a custom which is thus seen to exist
throughout Africa, in Siberia, China, India, Polynesia and the Americas.

  AUTHORITIES.--J.F. McLennan, _Primitive Marriage_ (1865), and _Studies
  in Anc. Hist._ (1896); Lord Avebury, _Origin of Civilization_ (1902);
  Westermarck, _History of Human Marriage_ (1894); A. Lang, _Social
  Origins_ (1903); L.H. Morgan, _Ancient Society_ (1877); J.G. Frazer,
  _Totemism and Exogamy_ (1910); see also TOTEM.

EXORCISM (Gr. [Greek: exorkizein], to conjure out), the expulsion of
evil spirits from persons or places by incantations, magical rites or
other means. As a corollary of the animistic theory of diseases and of
belief in Possession (q.v.), we find widely spread customs whose object
is to get rid of the evil influences. These customs may take the form of
a general expulsion of evils, either once a year or at irregular
intervals; the evils, which are often regarded as spirits, sometimes as
the souls of the dead, may be expelled, according to primitive
philosophy, either immediately by spells, purifications or some form of
coercion; or they may be put on the back of a scapegoat or other
material vehicle. Among the means of compelling the evil spirits are
assaults with warlike weapons or sticks, the noise of musical
instruments or of the human voice, the use of masks, the invocation of
more powerful good spirits, &c.; both fire and water are used to drive
them out, and the use of iron is a common means of holding them at bay.

The term exorcism is applied more especially to the freeing of an
individual from a possessing or disease-causing spirit; the means
adopted are frequently the same as those mentioned above; in the East
Indies the sufferer sometimes dances round a small ship, into which the
spirit passes and is then set adrift. The patient may be beaten or means
may be employed whose efficiency depends largely on their suggestive
nature. Among the Dakota Indians the medicine-man chants _hi-le-li-lah!_
at the bed of the sick man and accompanies his chant with the rattle; he
then sucks at the affected part till the possessing spirit is supposed
to come out and take its flight, when men fire guns at it from the door
of the tent. The Zulus believe that they can get rid of the souls of the
dead, which cause diseases, by sacrifices of cattle, or by expostulating
with the spirits; so too the _shaman_ or magician in other parts of the
world offers the possessing spirit objects or animals.

The professional exorcist was known among the Jews; in Greece the art
was practised by women, and it is recorded that the mothers of Epicurus
and Aeschines belonged to this class; both were bitterly reproached, the
one by the Stoics, the other by Demosthenes, with having taken part in
the practices in question. The prominence of exorcism in the early ages
of the Christian church appears from its frequent mention in the
writings of the fathers, and by the 3rd century there was an order of
exorcists (see EXORCIST). The ancient rite of exorcism in connexion with
baptism is still retained in the Roman ritual, as is also a form of
service for the exorcising of possessed persons. The exorcist signs the
possessed person with the figure of the cross, desires him to kneel, and
sprinkles him with holy water; after which the exorcist asks the devil
his name, and abjures him by the holy mysteries of the Christian
religion not to afflict the person possessed any more. Then, laying his
right hand on the demoniac's head, he repeats the form of exorcism as
follows: "I exorcise thee, unclean spirit, in the name of Jesus Christ;
tremble, O Satan, thou enemy of the faith, thou foe of mankind, who hast
brought death into the world, who hast deprived men of life, and hast
rebelled against justice, thou seducer of mankind, thou root of evil,
thou source of avarice, discord and envy." Houses and other places
supposed to be haunted by unclean spirits are likewise to be exorcised
with similar rites, and in general exorcism has a place in all the
ceremonies for consecrating and blessing persons or things (see
BENEDICTION).

  See Tylor, _Primitive Culture_; Skeat, _Malay Magic_, p. 427 seq.;
  Frazer, _Golden Bough_, vol. iii. 189; Krafft, _Ausführliche Historie
  von Exorcismus_; Koldeweg, _Der Exorcismus im Herzogthum
  Braunschweig_; Brecher, _Das Transcendentale, Magie, etc. im Talmud_,
  pp. 195-203: _Zeitschr. für Assyriologie_ (Dec. 1893, April 1894);
  Herzog, _Realencykl., s.v._ "Exorcismus"; Waldmeier, _Autobiography_,
  p. 64; L.W. King, _Babylonian Magic_; Maury, _La Magie_; R.C.
  Thompson, _Devils and Evil Spirits of Babylonia_.

EXORCIST (Lat. _exorcista_, Gr. [Greek: exorkistês]), in the Roman
Catholic church, the third grade in the minor orders of the clergy,
between those of acolyte and reader. The office, which involves the
right of ceremonially exorcising devils (see Exorcism), is actually no
more than a preliminary stage of the priesthood. The earliest record of
the special ordination of exorcists is the 7th canon of the council of
Carthage (A.D. 256). "When they are ordained," it runs, "they receive
from the hand of the bishop a little book in which the exorcisms are
written, receiving power to lay hands on the _energumeni_, whether
baptized or catechumens." Whatever its present position, the office of
exorcist was, until comparatively recent times, by no means considered a
sinecure. "The exorcist a terror to demons" (Paulinus, _Epist._ 24)
survived the Reformation among Protestants, with the belief, expressed
by Firmilianus in his epistle to St Cyprian, that "through the
exorcists, by the voice of man and the power of God, the devil may be
whipped, and burnt and tortured."

EXOTIC (Gr. [Greek: exôtikos], foreign, from [Greek: exô], outside), of
foreign origin, or belonging to another country. The term is now used in
the restricted sense of something not indigenous or native, and is
mostly applied to plants introduced from foreign countries, which have
not become acclimatized. Figuratively, "exotic" is used to convey the
sense of something rare, delicate or extravagant.

EXPATRIATION (from Late Lat. _expatriare_, to exile, and _patria_,
native land), a term used in a general sense for the banishment of a
person from his own country. In international law expatriation is the
renunciation or change of allegiance to one's native or adopted country.
It may take place either by a voluntary act or by operation of law. Some
countries, as France and England, disclaim their subjects if they become
naturalized in another country, others, again, passively permit
expatriation whether a new nationality has been acquired or not; others,
as Germany, make expatriation the consequence of continued absence from
their territory. (See ALIEN; ALLEGIANCE; NATURALIZATION.)

EXPERT (Lat. _expertus_, from _experiri_, to try), strictly, skilled, or
one who has special knowledge; as used in law, an expert is a person,
selected by a court, or adduced by a party to a cause, to give his
opinion on some point in issue with which he is peculiarly conversant.
In Roman law questions of disputed handwriting were referred to experts;
and in France, whenever the court considers that a report by experts is
necessary, it is ordered by a judgment clearly setting forth the objects
of the _expertise_ (Code Proc. Civ. art. 302). Three experts are then to
be appointed, unless the parties agree upon one only (art. 303). The
experts are required to take an oath (art. 305), but in practice this
requirement is frequently dispensed with. They may be challenged on the
same grounds as witnesses (art. 310). The necessary documentary and
other evidence is laid before them (art. 317), and they make a single
report to the court, even if they express different opinions: in that
case the grounds only of the different opinions are to be stated, and
not the personal opinion of each of the experts (art. 318). If the court
is not satisfied with the report, new experts may be appointed (art.
322); the judges are not bound to adopt the opinion of the experts (art.
323). "This procedure in regard to experts is common to both the civil
and commercial courts, but it is much more frequently resorted to in the
commercial court than in the civil court, and the investigation is
usually conducted by special experts officially attached to each of
these courts" (Bodington, _French Law of Evidence_, London, 1904, p.
102). A similar system is to be found in force in many other European
countries; see e.g. Codes of Civil Procedure of Holland, arts. 222 et
seq.; Belgium, arts. 302 et seq.; Italy, arts. 252 et seq.; as well as
in those colonies where French law has been followed (Codes of Civil
Procedure of Quebec, arts. 392 et seq.; St Lucia, arts. 286 et seq.). In
Mauritius the articles of the French law, summarized above, are still
nominally in force; but in practice each side calls its own expert
evidence, as in England.

There is some evidence that in England the courts were in early times in
the habit of summoning to their assistance, apparently as assessors,
persons specially qualified to advise upon any scientific or technical
question that required to be determined. Thus "in an appeal of maihem
(i.e. wounding) ... the court did not know how to adjudge because the
wound was new, and then the defendant took issue and prayed the court
that the maihem might be examined, on which a writ was sent to the
sheriff to cause to come _medicos chirurgieos de melioribus London, ad
informandum dominum regem el curiam de his quae eis ex parte domini
regis injungerentur_" (Year Book, 21 Hen. VII. pl. 30, p. 33). The
practice of calling in expert assistance in judicial inquiries was not
confined to medico-legal cases. "If matters arise," said Justice
Saunders in _Buckley_ v. _Rice Thomas_ (1554, Plowden, 124 a), "which
concern other faculties, we commonly apply for the aid of that science
or faculty which it concerns." English procedure, however, being
_litigious_, and not, like continental European procedure,
_inquisitorial_, in its character, the expert soon became, and still is,
simply a witness to speak to matters of opinion.

There is a considerable body of law in England as to expert evidence.
Only a few points can be touched upon here. (1) An expert is permitted
to refresh his memory in regard to any fact by referring to anything
written by himself or under his direction at the time when the fact
occurred or at a time when it was fresh in his memory. This is also law
generally in the United States (see e.g. New York Civil Code, s. 1843).
In Scotland, medical and other scientific reports are lodged in process
before the trial, and the witness reads them as part of his evidence and
is liable to be examined or cross-examined on their contents. (2) In
strictness, an expert will not be allowed, in cases of alleged insanity,
to say that a litigating or incriminated party is insane or the reverse,
and so to usurp the prerogative of the court or jury. But he may be
asked whether certain facts or symptoms, _assuming them to be proved_,
are or are not indicative of insanity. But in practice this rule is
relaxed both in England and in Scotland, and (where it exists) to a
still greater extent in America. (3) Foreign law can only be proved in
English courts--and the same rule applies in Scotland--(a) by obtaining
an opinion on the subject from a superior court of the country whose
laws are in dispute under the Foreign Law Ascertainment Act 1861 or the
British Law Ascertainment Act 1859, or (b) by the evidence of a lawyer
of the country whose law is in question, or who has studied it _in that
country_, or of an official whose position requires, and therefore
presumes, a sufficient knowledge of that law. (4) The weight of
authority both in England and in America supports the view that an
expert is not bound to give evidence as to matters of opinion unless
upon an undertaking by the party calling him to pay a reasonable
remuneration for his evidence.

Statutory provision has been made in England for the summoning of expert
assistance by the legal tribunals in various cases. In the county courts
the judge may, if he thinks fit, on the application of either party,
call in as assessor one or more persons of skill and experience as to
the matters in dispute (County Courts Act 1888, s. 103), and special
provision is made for calling in an assessor in employers' liability
cases (act of 1880, s. 6) and admiralty matters (see County Courts
Admiralty Jurisdiction Acts of 1868 and 1869). In the High Court and
court of appeal one or more specially qualified assessors may be called
in to assist in the hearing of any cause or matter except a criminal
proceeding by the crown (Judicature Acts 1873, s. 56), and a like power
is given to both these courts and the judicial committee of the privy
council in patent cases (Patents, &c., Act 1883., s. 28). Maritime
causes, whether original or on appeal from county courts, are usually
taken in the presence of Elder Brethren of the Trinity House, who advise
the judge without having any right to control or any responsibility for
his decision (see the "Beryl," 1884, 9 P.D. 1), and on appeal in
maritime causes nautical assessories are usually called in by the court
of appeal, and may be called in by the House of Lords (Judicature Act
1891, s. 3); a like provision is made as to maritime causes in Scottish
courts (Nautical Assessors [Scotland] Act 1894). The judicial committee
of the privy council, besides its power to call in assessors in patent
cases, is authorized to call them in in ecclesiastical causes (Appellate
Jurisdiction Act 1876, s. 14).

  In addition to the authorities cited in the text, see Taylor, _Law of
  Evidence_ (9th ed., London, 1895); J.D. Lawson, _Law of Expert and
  Opinion Evidence_ (1900).

EXPLOSIVES, a general term for substances which by certain treatment
"explode," i.e. decompose or change in a violent manner so as to
generate force. From the manner and degree of violence of the
decomposition they are classified into "propellants" and "detonators,"
but this classification is not capable of sharp delimitation. In some
cases the same substance may be employed for either purpose under
altered external conditions; but there are some substances which could
not possibly be employed as propellants, and others which can scarcely
be induced to explode in the manner known as "detonation." A propellant
may be considered as a substance that on explosion produces such a
disturbance that neighbouring substances are thrown to some distance; a
detonator or disruptor may produce an extremely violent disturbance
within a limited area without projecting substances to any great
distance. Time is an important, perhaps the most important, factor in
this action. A propellant generally acts by _burning_ in a more or less
rapid and regular manner, producing from a comparatively small volume a
large volume of gases; during this action heat is also developed, which,
being expended mostly on the gaseous products, causes a further
expansion. The noise accompanying an explosion is due to an air wave,
and is markedly different in the case of a detonator from a real
propellant. Some cases of ordinary combustion can be accelerated into
explosions by increasing the area of contact between the combustible and
the oxygen supplier, for instance, ordinary gas or dust explosions.
Neither temperature nor quantity of heat energy necessarily gives an
explosive action. Some metals, e.g. aluminium and magnesium, will, in
oxidizing, produce a great thermal effect, but unless there be some
gaseous products no real explosive action.

Explosives may be mechanical mixtures of substances capable of chemical
interaction with the production of large volumes of gases, or definite
chemical compounds of a peculiar class known as "endothermic," the
decomposition of which is also attended with the evolution of gases in
large quantity.

  All chemical compounds are either "endothermic" or "exothermic." In
  endothermic compounds energy, in some form, has been taken up in the
  act of formation of the compound. Some of this energy has become
  potential, or rather the compound formed has been raised to a higher
  potential. This case occurs when two elements can be united only under
  some compulsion such as a very high temperature, by the aid of an
  electric current, or spark, or as a secondary product whilst some
  other reactions are proceeding. For example, oxygen and nitrogen
  combine only under the influence of an electric spark, and carbon and
  calcium in the electric furnace. The formation of chlorates by the
  action of chlorine on boiling potash is a good instance of a complex
  compound (potassium chlorate), being formed in small quantity as a
  secondary product whilst a large quantity of primary and simpler
  products (potassium chloride and water) is forming. In chlorate
  formation the greater part of the reaction represents a running down
  of energy and formation of exothermic compounds, with only a small
  yield of an endothermic substance. Another idea of the meaning of
  endothermic is obtained from acetylene. When 26 parts by weight of
  this substance are burnt, the heat produced will warm up 310,450 parts
  of water 1° C. Acetylene consists of 24 parts of carbon and 2 of
  hydrogen by weight. The 24 parts of carbon will, if in the form of
  pure charcoal, heat 192,000 parts of water 1°, and the 2 parts of
  hydrogen will heat 68,000 parts of water 1°, the total heat production
  being 260,000 heat units. Thus 26 grams of acetylene give an excess of
  50,450 units over the amount given by the constituents. This excess of
  heat energy[1] is due to some form of potential energy in the
  compound which becomes actual heat energy at the moment of dissolution
  of the chemical union. The manner in which a substance is endothermic
  is of importance as regards the practical employment of explosives.
  Some particular endothermic state or form results from the mode of
  formation and the consequent internal structure of the molecule.
  Physical structure alone can be the cause of a relative endothermic
  state, as in the glass bulbs known as Rupert's drops, &c., or even in
  chilled steel. Rupert's drops fly in pieces on being scratched or cut
  to a certain depth. The cause is undoubtedly to be ascribed to the
  molecular state of the glass brought about by chilling from the melted
  state. The molecules have not had time to separate or arrange
  themselves in easy positions. In steel when melted the carbide of iron
  is no doubt diffused equally throughout the liquid. When cooled slowly
  some carbide separates out more or less, and the steel is soft or
  annealed. When chilled the carbides are retained in solid solution.
  The volume of chilled glass or steel differs slightly from that in the
  annealed state.

  Superfused substances are probably in a similar state of physical
  potential or strain. Many metallic salts, and organic compounds
  especially, will exhibit this state when completely melted and then
  allowed to cool in a clean atmosphere. On touching with a little of
  the same substance in a solid state the liquids will begin to
  crystallize, at the same time becoming heated almost up to their
  melting-points. The metal gallium shows this excellently well, keeping
  liquid for years until touched with the solid metal, when there is a
  considerable rise of temperature as solidification takes place.

  All carbon compounds, excepting carbon dioxide, and many if not all
  compounds of nitrogen, are endothermic. Most of the explosives in
  common use contain nitrogen in some form.

  Exothermic compounds are in a certain sense the reverse of
  endothermic; they are relatively inert and react but slowly or not at
  all, unless energy be expended upon them from outside. Water, carbon
  dioxide and most of the common minerals belong to this class.

The explosives actually employed at the present time include mixtures,
such as gunpowders and some chlorate compositions, the ingredients of
which separately may be non-explosive; compounds used singly, as
guncotton, nitroglycerin (in the form of dynamite), picric acid (as
lyddite or melinite), trinitrotoluene, nitrocresols, mercury fulminate,
&c.; combinations of some explosive compounds, such as cordite and the
smokeless propellants in general use for military purposes; and,
finally, blasting and detonating or igniting compositions, some of which
contain inert diluting materials as well as one or more high explosives.
Many igniting compositions are examples of the last type, consisting of
a high explosive diluted with a neutral substance, and frequently
containing in addition a composition which is inflamed by the explosion
of the diluted high explosive, the flame in turn igniting the actual
propellant.

_Explosive Mixtures._--The explosive mixture longest known is
undoubtedly gunpowder (q.v.) in some form--that is, a mixture of
charcoal with sulphur and nitre, the last being the oxygen provider.
Besides the nitrates of metals and ammonium nitrate, there is a limited
number of other substances capable of serving in a sufficiently
energetic manner as oxygen providers. A few chlorates, perchlorates,
permanganates and chromates almost complete the list. Of these the
sodium, potassium and barium chlorates are best known and have been
actually tried, in admixture with some combustible substances, as
practical explosives. Most other metallic chlorates are barred from
practical employment owing to instability, deliquescence or other
property.

Of the chlorates those of potassium and sodium are the most stable, and
mixtures of either of these salts with sulphur or sulphides, phosphorus,
charcoal, sugar, starch, finely-ground cellulose, coal or almost any
kind of organic, i.e. carbon, compound, in certain proportions, yield an
explosive mixture. In many cases these mixtures are not only fired or
exploded by heating to a certain temperature, but also by quite moderate
friction or percussion. Consequently there is much danger in manufacture
and storage, and however these mixtures have been made up, they are
quite out of the question as propellants on account of their great
tendency to explode in the manner of a detonator. In addition they are
not smokeless, and leave a considerable residue which in a gun would
produce serious fouling.

Mixtures of chlorates with aromatic compounds such as the nitro- or
dinitro-benzenes or even naphthalene make very powerful blasting agents.
The violent action of a chlorate mixture is due first to the rapid
evolution of oxygen, and also to the fact that a chlorate can be
detonated when alone. A drop of sulphuric acid will start the combustion
of a chlorate mixture. In admixture with sulphur, sulphides and
especially phosphorus, chlorates give extremely sensitive compositions,
some of which form the basis of friction tube and firing mixtures.

Potassium and sodium perchlorates and permanganates make similar but
slightly less sensitive explosive mixtures with the above-mentioned
substances. Finely divided metals such as aluminium or magnesium give
also with permanganates, chlorates or perchlorates sensitive and
powerful explosives. Bichromates, although containing much available
oxygen, form but feeble explosive mixtures, but some compounds of
chromic acid with diazo compounds and some acetylides are extremely
powerful as well as sensitive. Ammonium bichromate is a self-combustible
after the type of ammonium nitrate, but scarcely an explosive.

_Explosive Compounds._--Nearly all the explosive compounds in actual use
either for blasting purposes or as propellants are nitrogen compounds,
and are obtained more or less directly from nitric acid. Most of the
propellants at present employed consist essentially of nitrates of some
organic compound, and may be viewed theoretically as nitric acid, the
hydrogen of which has been replaced by a carbon complex; such compounds
are expressed by M·O·NO2, which indicates that the carbon group is in
some manner united by means of oxygen to the nitrogen group. Guncotton
and nitroglycerin are of this class. Another large class of explosives
is formed by a more direct attachment of nitrogen to the carbon complex,
as represented by M·NO2. A number of explosives of the detonating type
are of this class. They contain the same proportions of oxygen and
nitrogen as nitrites, but are not nitrites. They have been termed
nitro-derivatives for distinction. One of the simplest and longest-known
members of this group is nitrobenzene, C6H5NO2, which is employed to
some extent as an explosive, being one ingredient in rack-a-rock and
other blasting compositions. The dinitro-benzenes, C6H4(NO2)2, made from
it are solids which are somewhat extensively employed as constituents of
some sporting powders, and in admixture with ammonium nitrate form a
blasting powder of a "flameless" variety which is comparatively safe in
dusty or "gassy" coal seams.

Picric acid or trinitrophenol, C6H2·OH·(NO2)3 is employed as a high
explosive for shell, &c. It requires, however, either to be enclosed and
heated, or to be started by a powerful detonator to develop its full
effect. Its compounds with metals, such as the potassium salt,
C6H2·OK·(NO2)3, are when dry very easily detonated by friction or
percussion and _always_ on heating, whereas picric acid itself will burn
very quietly when set fire to under ordinary conditions.
Trinitrotoluene, C6H2·CH3·(NO2)3, is a high explosive resembling picric
acid in the manner of its explosion (to which in fact it is a rival),
but differs therefrom in not forming salts with metals. The
nitronaphthols, C10H6·OH·NO2, and higher nitration products may be
counted in the list. Their salts with metals behave much like the
picrates.

All these nitro compounds can be reduced by the action of nascent
hydrogen to substances called amines (q.v.), which are not always
explosive in themselves, but in some cases can form nitrates of a
self-combustible nature. Aminoacetic acid, for instance, will form a
nitrate which burns rapidly but quietly, and might be employed as an
explosive. By the action of nitrous acid at low temperatures on aromatic
amines, e.g. aniline, C6H5NH2, diazo compounds are produced. These are
all highly explosive, and when in a dry state are for the most part also
extremely sensitive to friction, percussion or heat. As many of these
diazo compounds contain no oxygen their explosive nature must be
ascribed to the peculiar state of union of the nitrogen. This state is
attempted to be shown by the formulae such as, for instance, C6H5·N :
N·X, which maybe some compound of diazobenzene. Probably the most
vigorous high explosive at present known is the substance called
hydrazoic acid or azoimide (q.v.). It forms salts with metals such as
AgN3, which explode in a peculiar manner. The ammonium compound, NH4N3,
may become a practical explosive of great value.

Mercuric fulminate, HgC2N2O2, is one of the most useful high explosives
known. It is formed by the action of a solution of mercurous nitrate,
containing some nitrous acid, on alcohol. It is a white crystalline
substance almost insoluble in cold water and requiring 130 times its
weight of boiling water for solution. It may be heated to 180° C. before
exploding, and the explosion so brought about is much milder than that
produced by percussion. It forms the principal ingredient in cap
compositions, in many fuses and in detonators. In many of these
compositions the fulminate is diluted by mixture with certain quantities
of inert powders so that its sensitiveness to friction or percussion is
just so much lowered, or slowed down, that it will fire another mixture
capable of burning with a hot flame. For detonating dynamite, guncotton,
&c., it is generally employed without admixture of a diluent.

_Smokeless Propellants._--Gunpowders and all other explosive mixtures or
compounds containing metallic salts must form smoke on combustion. The
solids produced by the resolution of the compounds are in an extremely
finely-divided state, and on being ejected into the atmosphere become
more or less attached to water vapour, which is so precipitated, and
consequently adds to the smoke. The simplest examples of propellants of
the smokeless class are compressed gases. Compressed air was the
propellant for the Zalinski dynamite gun. Liquefied carbon dioxide has
also been proposed and used to a slight extent with the same idea. It is
scarcely practical, however, because when a quantity of a gas liquefied
by pressure passes back again into the gaseous state, there is a great
absorption of heat, and any remaining liquid, and the containing vessel,
are considerably cooled. Steam guns were tried in the American Civil War
in 1864; but a steam gun is not smokeless, for the steam escaping from
the long tube or gun immediately condenses on expansion, forming white
mist or smoke.

At the earliest stage of the development of guncotton the advantage of
its smokeless combustion was fully appreciated (see GUNCOTTON). That it
did not at once take its position as _the_ smokeless propellant, was
simply due to its physical state--a fibrous porous mass--which burnt too
quickly or even detonated under the pressure required in fire-arms of
any kind. In the early eighties of the 19th century it was found that
several substances would partly dissolve or at least gelatinize
guncotton, and the moment when guncotton proper was obtained as a
colloid or jelly was the real start in the matter of smokeless
propellants.

Guncotton is converted into a gelatinous form by several substances,
such as esters, e.g. ethyl acetate or benzoate, acetone and other
ketones, and many benzene compounds, most of which are volatile liquids.
On contact with the guncotton a jelly is formed which stiffens as the
evaporation of the gelatinizing agent proceeds, and finally hardens when
the evaporation is complete. Whilst in a stiff pasty state it may be
cut, moulded or pressed into any desired shape without any danger of
ignition. In fact guncotton in the colloid state may be hammered on an
anvil, and, as a rule, only the portion struck will detonate or fire.
Guncotton alone makes a very hard and somewhat brittle mass after
treatment with the gelatinizing agent and complete drying, and small
quantities of camphor, vaseline, castor oil and other substances are
incorporated with the gelatinous guncotton to moderate this hard and
brittle state.

All the smokeless powders, of which gelatinized guncottons or nitrated
celluloses are the base, are moulded into some conveniently shaped
grain, e.g. tubes, cords, rods, disks or tablets, so that the rate of
burning may be controlled as desired. The Vieille powder, invented in
1887 and adopted in France for a magazine rifle, consisted of
gelatinized guncotton with a little picric acid. Later a mixture of two
varieties of guncotton gelatinized together was used. In addition to
guncottons other explosive or non-explosive substances are contained in
some of these powders. Guncotton alone in the colloid state burns very
slowly if in moderate-sized pieces, and when subdivided or made into
thin rods or strips it is still very mild as an explosive, partly from a
chemical reason, viz. there is not sufficient oxygen in it to burn the
carbon to dioxide. Many mixtures are consequently in use, and many more
have been proposed, which contain some metallic salt capable of
supplying oxygen, such as barium or ammonium nitrate, &c., the idea
being to accelerate the rate of burning of the guncotton and if possible
avoid the production of smoke.

The discovery by A. Nobel that nitroglycerin could be incorporated with
collodion cotton to form blasting gelatin (see DYNAMITE) led more or
less directly to the invention of ballistite, which differs from
blasting gelatin only in the relative amounts of collodion, or soluble
nitrated cotton, and nitroglycerin. Ballistite was adopted by the
Italian government in 1890 as a military powder. Very many substances
and mixtures have been proposed for smokeless powder, but the two
substances, guncotton and nitroglycerin, have for the most part kept the
field against all other combinations, and for several reasons.
Nitroglycerin contains a slight excess of oxygen over that necessary to
convert the whole of the carbon into carbon dioxide; it burns in a more
energetic manner than guncotton; the two can be incorporated together in
any proportion whilst the guncotton is in the gelatinous state; also all
the liquids which gelatinize guncotton dissolve nitroglycerin, and, as
these gelatinizing liquids evaporate, the nitroglycerin is left
entangled in the guncotton jelly, and then shares more or less its
colloidal character. In burning the nitroglycerin is protected from
detonation by the gelatinous state of the guncotton, but still adds to
the rate of burning and produces a higher temperature.

  _Desirable Qualities._--Smokelessness is one only of the desirable
  properties of a propellant. All the present so-called smokeless
  powders produce a little fume or haze, mainly due to the condensation
  of the steam which forms one of the combustion products. There is
  often also a little vapour from the substances, such as oils, mineral
  jelly, vaseline or other hydrocarbon added for lubrication or to
  render the finished material pliable, &c. The gases produced should
  neither be very poisonous nor exert a corrosive action on metals, &c.
  The powder itself should have good keeping qualities, that is, not be
  liable to chemical changes within ordinary ranges of temperature or in
  different climates when stored for a few years. In these powders
  slight chemical changes are generally followed by noticeable ballistic
  changes. All the smokeless powders of the present day produce some
  oxide of nitrogen, traces of which hang about the gun after firing and
  change rapidly into nitrous and nitric acids. Nitrous acid is
  particularly objectionable in connexion with metals, as it acts as a
  carrier of oxygen. The fouling from modern smokeless powders is a
  slight deposit of acid grease, and the remedy consists in washing out
  the bore of the piece with an alkaline liquid. The castor oil, mineral
  jelly or camphor, and similar substances added to smokeless powders
  are supposed to act as lubricants to some extent. They are not as
  effective in this respect as mineral salts, and the rifling of both
  small-arms and ordnance using smokeless powders is severely gripped by
  the metal of the projectile. The alkaline fouling produced by the
  black and brown powders acted as a preventive of rusting to some
  extent, as well as a lubricant in the bore.

  _Danger in Manufacture._--In the case of the old gunpowders, the most
  dangerous manufacturing operation was incorporation. With the modern
  colloid propellants the most dangerous operations are the chemical
  processes in the preparation of nitroglycerin, the drying of
  guncotton, &c. After once the gelatinizing solvent has been added, all
  the mechanical operations can be conducted, practically, with perfect
  safety. This statement appears to be correct for all kinds of nitrated
  cellulose powders, whether mixed with nitroglycerin or other
  substances. Should they become ignited, which is possible by a rise of
  temperature (to say 180°) or contact with a flame, the mixture burns
  quickly, but does not detonate.

  As a rule naval and military smokeless powders are shaped into flakes,
  cubes, cords or cylinders, with or without longitudinal perforations.
  All the modifications in shape and size are intended to regulate the
  rate of burning. Sporting powders are often coloured for trade
  distinction. Some powders are blackleaded by glazing with pure
  graphite, as is done with black powders. One object of this glazing is
  to prevent the grains or pieces becoming joined by pressure; for rods
  or pieces of some smokeless powders might possibly unite under
  considerable pressure, producing larger pieces and thus altering the
  rate of burning. Most smokeless powders are fairly insensitive to
  shock. All these gelatinized powders are a little less easily ignited
  than black powders. A slightly different cap composition is required
  for small-arm cartridges, and cannon cartridges generally require a
  small primer or starter of powdered black gunpowder.

  It is desired that a propellant shall produce the maximum velocity
  with the minimum pressure. The pressure should start gently so that
  the inertia of the projectile is overcome without any undue local
  strain on the breech near the powder chamber, and more especially that
  as more and more space is given to the gases by the movement of the
  projectile up the gun to the muzzle, gas should be produced with
  sufficient rapidity to keep the pressure nearly uniform or slightly
  increasing along the bore. The leading idea for improvements in
  relation to propellants is to obtain the greatest possible pressure
  regularly developed, and at the same time the lowest temperatures.
       (W. R. E. H.)

_Law._--In 1860 an act was passed in England "to amend the law
concerning the making, keeping and carriage of gunpowder and
compositions of an explosive nature, and concerning the manufacture and
use of fireworks" (23 & 24 Vict. c. 139), whereby previous acts on the
same subject were repealed, and minute and stringent regulations
introduced. Amending acts were passed in 1861 and 1862. In 1875 was
passed the Explosives Act (38 & 39 Vict. c. 17), which repealed the
former acts, and dealt with the whole subject in a more comprehensive
manner. This act, containing 122 sections, and applying to Scotland and
Ireland, as well as to England, constitutes, with various orders in
council and home office orders, a complete code. The act of 1875 was
based on the report of a committee of the House of Commons, public
opinion having been greatly excited on the subject by a terrible
explosion on the Regent's Canal in 1874. Explosives are thus defined:
(1) Gunpowder, nitroglycerin, dynamite, guncotton, blasting powders,
fulminate of mercury or of other metals, coloured fires, and every other
substance, whether similar to those above-mentioned or not, used or
manufactured with a view to produce a practical effect by explosion or a
pyrotechnic effect, and including (2) fog-signals, fireworks, fuses,
rockets, percussion caps, detonators, cartridges, ammunition of all
descriptions, and every adaptation or preparation of an explosive as
above defined. Part i. deals with gunpowder, providing that it shall be
manufactured only at factories lawfully existing or licensed under the
act; that it shall be kept (except for private use) only in existing or
new magazines or stores, or in registered premises, licensed under the
act. Private persons may keep gunpowder for their own use to the amount
of thirty pounds. The act also prescribes rules for the proper keeping
of gunpowder on registered premises. Part ii. deals with nitroglycerin
and other explosives; part iii. with inspection, accidents, search, &c.;
part iv. contains various supplementary provisions. By order in council
the term "explosive" may be extended to any substance which appears to
be specially dangerous to life or property by reason of its explosive
properties, or to any process liable to explosion in the manufacture
thereof, and the provisions of the act then extend to such substance
just as if it were included in the term "explosive" in the act. The act
lays down minute and stringent regulations for the sale of gunpowder,
restricting the sale thereof in public thoroughfares or places, or to
any child apparently under the age of thirteen; requiring the sale of
gunpowder to be in closed packages labelled; it also lays down general
rules for conveyance, &c. The act also gives power by order in council
to define, from time to time, the composition, quality and character of
any explosive, and to classify explosives, and such orders in council
are frequently made including new substances; those in force will be
found in the _Statutory Rules and Orders_, tit. "explosive substance."
The Merchant Shipping Act 1894 imposes restrictions on the carriage of
dangerous goods in a British or foreign vessel, "dangerous goods"
meaning aquafortis, vitriol, naphtha, benzine, gunpowder, lucifer
matches, nitroglycerin, petroleum and any explosive within the meaning
of the Explosives Act 1875. The act is administered by the home office,
and an annual report is published containing the proceedings of the
inspectors of explosives and an account of the working of the act. Each
annual report gives a list of explosives at the time authorized for
manufacture or importation, and appendices containing information as to
accidents, experiments, &c.

Practically every European country has legislated on the lines of the
English act of 1875, Austria taking the lead, in 1877, with an
explosives ordinance almost identical with the English act. The United
States and the various English colonies also have explosives acts
regulating the manufacture, storage and importation of explosives. (See
also PETROLEUM.)     (T. A. I.)

  BIBLIOGRAPHY.--M. Berthelot, _Sur la force des matières explosives_
  (Paris, 1883); P.F. Chalon, _Les Explosifs modernes_ (Paris, 1886);
  W.H. Wardell, _Handbook of Gunpowder and Guncotton_ (London, 1888);
  J.P. Cundill, _A Dictionary of Explosives_ (London, 1889 and 1897); M.
  Eissler, _A Handbook of Modern Explosives_ (London, 1896, new ed.
  1903); J.A. Longridge, _Smokeless Powder and its Influence on Gun
  Construction_ (London, 1890); C. Napier Hake and W. Macnab,
  _Explosives and their Power_ (London, 1892); G. Coralys, _Les
  Explosifs_ (Paris, 1893); A. Ponteaux, _La Poudre sans fumée et les
  poudres anciennes_ (Paris, 1893); F. Salvati, _Vocabolario di polveri
  ed explosivi_ (Rome, 1893); C. Guttmann, _The Manufacture of
  Explosives_ (London, 1895 and later); S.J. von Romocki, _Geschichte
  der Sprengstoffchemie, der Sprengtechnik und des Torpedowesens bis zum
  Beginn der neusten Zeit_ (Berlin, 1895); _Geschichte der
  Explosivstoffe, die rauchschwachen Pulver_ (Berlin, 1896); P.G.
  Sanford, _Nitro-explosives_ (London, 1896); L. Gody, _Traité théorique
  et pratique des matières explosives_ (Namur, 1896); R. Wille, _Der
  Plastomerite_ (Berlin, 1898); E. Sarrau, _Introduction à la théorie
  des explosifs_ (1893); _Théorie des explosifs_ (1896); O. Guttmann,
  _Manufacture of Explosives_ (London, 1895); E.M. Weaver, _Notes on
  Military Explosives_ (New York, 1906); M. Eissler, _The Modern High
  Explosives_ (New York, 1906); _Treatise on Service Explosives_,
  published by order of the secretary of state for war (London, 1907).
  Most of the literature on modern explosives, e.g. dynamite, &c., is to
  be found in papers contributed to scientific journals and societies.
  An index to those which have appeared in the _Journal of the Society
  of Chemical Industry_ is to be found in the decennial index (1908)
  compiled by F.W. Renant.

FOOTNOTE:

  [1] Not necessarily heat energy entirely. A number of
    substances--acetylides and some nitrogen compounds, such as nitrogen
    chloride--decompose with extreme violence, but _little heat_ is
    produced.

EXPRESS (through the French from the past participle of the Lat.
_exprimere_, to press out, by transference used of representing objects
in painting or sculpture, or of thoughts, &c. in words), a word
signifying that which is clearly and definitely set forth or
represented, explicit, and thus used of a meaning, a law, a contract and
the like, being specially contrasted with "implied." Thus in law,
malice, for which there is actual evidence, as apart from that which may
be inferred from the acts of the person charged, is known as "express."
The word is most frequently used with the idea of something done with a
definite purpose; the term "express train," now meaning one that travels
at a high speed over long distances with few intermediate stoppages,
was, in the early days of railways, applied to what is now usually
called a "special," i.e. a train not running according to the ordinary
time-tables of the railway company, but for some specific purpose, or
engaged by a private person. About 1845 this term became used for a
train running to a particular place without stopping. Similarly in the
British postal service, express delivery is a special and immediate
delivery of a letter, parcel, &c., by an express messenger at a
particular increased rate. The system was adopted in 1891.

In the United States of America, express companies for the rapid
transmission of parcels and luggage and light goods generally perform
the function of the post office or the railways in the United Kingdom
and the continent of Europe. Not only do they deliver goods, but by the
cash on delivery system (see CASH) the express companies act as agents
both for the purchaser and seller of goods. They also serve as a most
efficient agency for the transmission of money, the express money order
being much more easily convertible than the postal money orders, as the
latter can only be redeemed at offices in large and important towns. The
system dates back to 1839, when one William Frederick Harnden
(1813-1845), a conductor on the Boston and Worcester railway, undertook
on his own account the carrying of small parcels and the performance of
small commissions. Obliged to leave the company's service or abandon his
enterprise, he started an "express" service between Boston and New York,
carrying parcels, executing commissions and collecting drafts and bills.
Alvin Adams followed in 1840, also between Boston and New York. From
1840 to 1845 the system was adopted by many others between the more
important towns throughout the States. The attempt to carry letters
also was stopped by the government as interfering with the post office.
In 1854 began the amalgamation of many of the companies. Thus under the
name of the Adams Express Company the services started by Harnden and
Adams were consolidated. The lines connecting the west and east by
Albany, Buffalo and the lakes were consolidated in the American Express
Company, under the direction of William G. Fargo (q.v.), Henry Wells and
Johnston Livingston, while another company, Wells, Fargo & Co., operated
on the Pacific coast. The celebrated "Pony Express" was started in 1860
between San Francisco and St Joseph, Missouri, the time scheduled being
eight days. The service was carried on by relays of horses, with
stations 25 m. apart. The charge made for the service was $2.50 per ½
oz. The completion of the Pacific Telegraph Company line in 1861 was
followed by the discontinuance of the regular service.

The name "express" is applied to a rifle having high velocity, flat
trajectory and long fixed-sight ranges; and an "express-bullet" is a
light bullet with a heavy charge of powder used in such a rifle (see
RIFLE).

EXPROPRIATION, the taking away or depriving of property (Late Lat.
_expropriare_, to take away, _proprium_, i.e. that which is one's own).
The term is particularly applied to the compulsory acquisition of
private property by the state or other public authority.

EXPULSION (Lat. _expulsio_, from _expellere_), the act of driving out,
or of removing a person from the membership of a body or the holding of
an office, or of depriving him of the right of attending a meeting, &c.
In the United Kingdom the House of Commons can by resolution expel a
member. Such resolution cannot be questioned by any court of law. But
expulsion is only resorted to in cases where members are guilty of
offences rendering them unfit for a seat in the House, such as being in
open rebellion, being guilty of forgery, perjury, fraud or breach of
trust, misappropriation of public money, corruption, conduct unbecoming
the character of an officer and a gentleman, &c. It is customary to
order the member, if absent, to attend in his place, before an order is
made for his expulsion (see May, _Parliamentary Practice_, 1906, p. 56
seq.). Municipal corporations or other local government bodies have no
express power to expel a member, except in such cases where the law
declares the member to have vacated his seat, or where power is given by
statute to declare the member's seat vacant. In the cases of officers
and servants of the crown, tenure varies with the nature of the office.
Some officials hold their offices _ad vitam aut culpam or dum bene se
gesserunt_, others can be dismissed at any time and without reason
assigned and without compensation. In the case of membership of a
voluntary association (club, &c.) the right of expulsion depends upon
the rules, and must be exercised in good faith. Courts of justice have
jurisdiction to prevent the improper expulsion of the member of a
voluntary association where that member has a right of property in the
association. In the case of meetings, where the meeting is one of a
public body, any person not a member of the body is entitled to be
present only on sufferance, and may be expelled on a resolution of the
body. In the case of ordinary public meetings those who convene the
meeting stand in the position of licensors to those attending and may
revoke the licence and expel any person who creates disorder or makes
himself otherwise objectionable.

_Expulsion of Aliens._--Under the Naturalization Act of 1870, the last
of the civil disqualifications affecting aliens in England was removed.
The political disqualifications which remained only applied to electoral
rights. In the very exceptional cases in which it was retained in the
statute book, expulsion was considered to have fallen into desuetude,
but it has been revived by the Aliens Act of 1905 (5 Edw. VII. c. 13).
Under this act powers are given to the secretary of state to make an
order requiring an alien to leave the United Kingdom within a time fixed
by the order and thereafter to remain outside the United Kingdom,
subject to certain conditions, provided it is certified to him that the
alien has been convicted of any felony or misdemeanour or other offence
for which the court has power to impose imprisonment without the option
of a fine, &c., or that he has been sentenced in a foreign country with
which there is an extradition treaty, for a crime not being an offence
of a political character. There are also provisions applicable within
one year, after the alien has entered the United Kingdom in the case of
pauper aliens. Precautions are taken to prevent, as far as possible, any
abuse of the power of expulsion. Under the French law of expulsion
(December 3, 1849) there are no such precautions, the minister of the
interior having an absolute discretion to order any foreigner as a
measure of public policy to leave French territory and in fact to have
him taken immediately to the frontier.

EXTENSION (Lat. _ex_, out; _tendere_, to stretch), in general, the
action of straining or stretching out. It is usually employed
metaphorically (cf. the phrase an "extension of time," a period allowed
in excess of what has been agreed upon). It is used as a technical term
in logic to describe the total number of objects to which a given term
may be applied; thus the meaning of the term "King" in "extension" means
the kings of England, Italy, Spain, &c. (cf. DENOTATION), while in
"intension" it means the attributes which taken together make up the
idea of kinghood (see CONNOTATION). In psychology the literal sense of
extension is retained, i.e. "spread-outness." The perception of space by
the senses of sight and touch, as opposed to semi-spatial perceptions by
smell and hearing, is that of "continuous expanse composed of positions
separated and connected by distances" (Stout); to this the term
"extension" is applied. The perception of separate objects involves
position and distance, but these taken together are not extension, which
necessarily implies continuity. To move one's finger along the keys of a
piano gives both the position and the distance of the keys; to move it
along the frame gives the idea of extension. By expanding this idea we
obtain the conception of all space as an extended whole. To this
perception are necessary both form and material. It should be observed
the actual quality of a stimulus (rough, smooth, dry, &c.) has nothing
to do with the spatial perception as such, which is concerned purely
with what is known as "local signature." The elementary undifferentiated
sensation excited by the stimuli exerted by a continuous whole is known
as its "extensive quantity" or "extensity." The term has to do not with
the kind of object which excites the sensation, but simply with the
vague massiveness of the latter. As such it is distinguishable in
thought from extension, though it is not easy to say whether and if so
how far the quantitative aspect of space can exist apart from spatial
order. Extensity as an element in the complex of extension must be
carefully distinguished from intensity. Mere increase of pressure
implies increase of intensity of sensation; to increase the extensity
the _area_, so to speak, of the exciting stimulus must be increased.
Thus the extensity (also called "voluminousness," or "massiveness") of
the sensation produced by a roll of thunder is greater than that
produced by a whistle or the bark of a dog. It should be observed that
this application of the idea of extensity to sensation in general,
rather than to the matter which is the exciting stimulus, is only an
analogy, an attempt to explain a common psychic phenomenon by
terminology which is intrinsically suitable to the physical. As a
natural consequence the term represents different shades of meaning in
different treatises, verging sometimes towards the physical, sometimes
towards the psychic, meaning.

In connexion with extension elaborate psycho-physical experiments have
been devised,.e.g. with the object of comparing the accuracy of tactual
and visual perception and discovering what are the least differences
which each can observe. At a distance two lights appear as one, just as
two stars distinguishable through a telescope are one to the naked eye
(see VISION): again if the points of a compass are brought close
together and pressed lightly on the skin the sensation, though vague and
diffused, is a single one.

  See PSYCHOLOGY and works there quoted; also SPACE AND TIME.

EXTENUATING CIRCUMSTANCES. This expression is used in law with reference
to crimes, to describe cases in which, though an offence has been
committed without legal justification or excuse, its gravity, from the
point of view of punishment or moral opprobrium, is mitigated or reduced
by reason of the facts leading up to or attending the commission of the
offence. According to English procedure, the jury has no power to
determine the punishment to be awarded for an offence. The sentence,
with certain exceptions in capital cases, is within the sole discretion
of the judge, subject to the statutory prescriptions as to the kind and
maximum of punishment. It is common practice for juries to add to their
verdict, guilty or not guilty, a rider recommending the accused to mercy
on the ground of grave provocation received, or other circumstances
which in their view should mitigate the penalty. This form of rider is
often added on a verdict of guilty of wilful murder, a crime as to which
the judge has no discretion as to punishment, but the recommendation is
sent to the Home Office for consideration in advising as to exercise of
the prerogative of mercy. Quite independently of any recommendation by
the jury, the judge is entitled to take into account matters proved
during the trial, or laid before him after verdict, as a guide to him in
determining the quantum of punishment.

Under the French law (_Code d'instruction criminelle_, art. 345), it is
the sole right and the duty of a jury in a criminal case to pronounce
whether or not the commission of the offence was attended by extenuating
circumstances (_circonstances atténuantes_). They are not bound to say
anything about the matter, but the whole or the majority may qualify the
verdict by finding extenuation, and if they do, the powers of the court
to impose the maximum punishment are taken away and the sentence to be
pronounced is reduced in accordance with the scale laid down in art. 463
of the _Code pénal_. The most important result of this rule is to enable
a jury to prevent the infliction of capital punishment for murder. In
cases of what is termed "crime passionel," French juries, when they do
not acquit, almost invariably find extenuation; and a like verdict has
become common even in the case of cold-blooded and sordid murders, owing
to objections to capital punishment.

EXTERRITORIALITY, a term of international law, used to denominate
certain immunities from the application of the rule that every person is
subject for all acts done within the boundaries of a state to its local
laws. It is also employed to describe the quasi-extraterritorial
position, to borrow the phrase of Grotius, of the dwelling-place of an
accredited diplomatic agent, and of the public ships of one state while
in the waters of another. Latterly its sense has been extended to all
cases in which states refrain from enforcing their laws within their
territorial jurisdiction. The cases recognized by the law of nations
relate to: (1) the persons and belongings of foreign sovereigns, whether
incognito or not; (2) the persons and belongings of ambassadors,
ministers plenipotentiary, and other accredited diplomatic agents and
their suites (but not consuls, except in some non-Christian countries,
in which they sometimes have a diplomatic character); (3) public ships
in foreign waters. Exterritoriality has also been granted by treaty to
the subjects and citizens of contracting Christian states resident
within the territory of certain non-Christian states. Lastly, it is held
that when armies or regiments are allowed by a foreign state to cross
its territory, they necessarily have exterritorial rights. "The ground
upon which the immunity of sovereign rulers from process in our courts,"
said Mr Justice Wills in the case of _Mighell_ v. _Sultan of Johore_,
1804, "is recognized by our law, is that it would be absolutely
inconsistent with the status of an independent sovereign that he should
be subject to the process of a foreign tribunal," unless he deliberately
submits to its jurisdiction. It has, however, been held where the
foreign sovereign was also a British subject (_Duke of Brunswick_ v.
_King of Hanover_, 1844), that he is amenable to the jurisdiction of the
English Courts in respect of transactions done by him in his capacity as
a subject. A "foreign sovereign" may be taken to include the president
of a republic, and even a potentate whose independence is not complete.
Thus in the case, cited above, of _Mighell_ v. _Sultan of Johore_, the
sultan was ascertained to have abandoned all right to contract with
foreign states, and to have placed his territory under British
protection. The court held that he was, nevertheless, a foreign
sovereign in so far as immunity from British jurisdiction was concerned.
The immunity of a foreign diplomatic agent, as the direct representative
of a foreign sovereign (or state), is based on the same grounds as that
of the sovereign authority itself. The international practice in the
case of Great Britain was confirmed by an act of parliament of the reign
of Queen Anne, which is still in force. The preamble to this act states
that "turbulent and disorderly persons in a most outrageous manner had
insulted the person of the then ambassador of his Czarish Majesty,
emperor of Great Russia," by arresting and detaining him in custody for
several hours, "in contempt to the protection granted by Her Majesty,
contrary to the law of nations, and in prejudice of the rights and
privileges which ambassadors and other public ministers, authorized and
received as such, have at all times been thereby possessed of, and ought
to be kept sacred and inviolable." This preamble has been repeatedly
held by our courts to be declaratory of the English common law. The act
provides that all suits, writs, processes, against any accredited
ambassador or public minister or his domestic servant, and all
proceedings and judgments had thereupon, are "utterly null and void,"
and that any person violating these provisions shall be punished for a
breach of the public peace. Thus a foreign diplomatic agent cannot, like
the sovereign he represents, waive his immunity by submitting to the
British jurisdiction. The diplomatic immunity necessarily covers the
residence of the diplomatic agent, which some writers describe as
assimilated to territory of the state represented by the agent; but
there is no consideration which can justify any extension of the
immunity beyond the needs of the diplomatic mission resident within it.
It is different with public ships in foreign waters. In their case the
exterritoriality attaches to the vessel. Beyond its bulwarks captain and
crew are subject to the ordinary jurisdiction of the state upon whose
territory they happen to be. By a foreign public ship is now understood
any ship in the service of a foreign state. It was even held in the case
of the "Parlement Belge" (1880), a packet belonging to the Belgian
government, that the character of the vessel as a public ship was not
affected by its carrying passengers and merchandise for hire. In a more
recent case an action brought by the owners of a Greek vessel against a
vessel belonging to the state of Rumania was dismissed, though the
agents of the Rumanian government had entered an appearance
unconditionally and had obtained the release of the vessel on bail, on
the ground that the Rumanian government had not authorized acceptance of
the British jurisdiction (The "Jassy," 1906, 75 L.J.P. 93).

Writers frequently describe the exterritoriality of both embassies and
ships as absolute. There is, however, this difference, that the
exterritoriality of the latter not being, like that of embassies, a
derived one, there seems to be no ground for limitation of it. It was,
nevertheless, laid down by the arbitrators in the "Alabama" case
(Cockburn dissenting), that the privilege of exterritoriality accorded
to vessels had not been admitted into the law of nations as an absolute
right, but solely as a proceeding founded on the principle of courtesy
and mutual deference between different nations, and that it could
therefore "never be appealed to for the protection of acts done in
violation of neutrality."

The exterritorial settlements in the Far East, the privileges of
Christians under the arrangements made with the Ottoman Porte, and other
exceptions from local jurisdictions, are subject to the conditions laid
down in the treaties by which they have been created. There are also
cases in which British communities have grown up in barbarous countries
without the consent of any local authority. All these are regulated by
orders in council, issued now in virtue of the Foreign Jurisdiction Act
1890, an act enabling the crown to exercise any jurisdiction it may have
"within a foreign country" in as ample a manner as if it had been
acquired "by cession or conquest of territory." A very exceptional case
of exterritoriality is that granted to the pope under a special Italian
enactment.     (T. Ba.)

EXTORTION (Lat. _extorsio_, from _extorquere_, to twist out, to take
away by force), in English law the term applied to the exaction by
public officers of money or money's worth not due at all, or in excess
of what is due, or before it is due. Such exaction, unless made in good
faith (i.e. in honest mistake as to the sum properly payable), is a
misdemeanour by the common law and is punishable by fine and (or)
imprisonment. Besides the punishment above stated, an action for twice
the value of the thing extorted lies against officers of the king (1275,
3 Edw. I. c. 26). There are numerous provisions for the punishment of
particular officers who make illegal exactions or take illegal fees:
e.g. sheriffs and their officers (Sheriffs Act 1887), county court
bailiffs (County Courts Act 1888), clerks of courts of justice, and
gaolers who exact fees from prisoners. A gaoler is also punishable for
detaining the corpse of a prisoner as security for debt. The term
"public officer" is not limited to offices under the crown; and there
are old precedents of criminal proceedings for extortion against
churchwardens, and against millers and ferrymen who demand tolls in
excess of what is customary under their franchise.

The term extortion is also applied to the exaction of money or money's
worth by menaces of personal violence or by threats to accuse of crime
or to publish defamatory matter about another person. These offences
fall partly under the head of robbery and partly under blackmail, or
what in French is termed _chantage_.

  See _Russell on Crimes_ (6th ed., vol. i. p. 423; vol. iii. p. 348).

EXTRACT (from Lat. _extrahere_, to draw out), in pharmacy, the name
given to preparations formed by evaporating or concentrating solutions
of active principles; _tinctures_ are solutions which have not been
subjected to any evaporation. "Liquid extracts" are those of a syrupy
consistency, and are generally prepared by treating the drug with the
solvent (water, alcohol, &c.) and concentrating the solution until it
attains the desired consistency. "Ordinary extracts" are thick,
tenacious and sometimes even dry preparations; they are obtained by
evaporating solutions as obtained above, or the juices expressed from
the plants.

Extraction, in chemical technology, is a process for separating one
substance from another by taking advantage of the varying solubility of
the components in some chosen solvent. The term "lixiviation" is used
when water is the solvent. In laboratory practice all the common
solvents are employed. With small quantities it may suffice to shake the
substance with the solvent, the mixture being heated if necessary,
filter and distil or otherwise remove the solvent from the distillate.
For larger quantities continuous extraction is advisable. This may be
carried out in many forms of apparatus; one of the most convenient is
the Soxhlet extractor, in which the extract siphons into the flask
containing the solvent, and so maintains the quantity of available
solvent practically constant. Continuous extraction is generally the
practice in technology. One of the most important applications is in the
fat and gelatine industries.

EXTRADITION (Lat. _ex_, out, and _traditio_, handing over), the
surrender of an alleged criminal for trial by a foreign state where he
has taken refuge, to the state against which the alleged offence has
been committed. When a person who has committed an offence in one
country escapes to another, what is the duty of the latter with regard
to him? Should the country of refuge try him in its own courts according
to its own laws, or deliver him up to the country whose laws he has
broken? To the general question international law gives no certain
answer. Some jurists, Grotius among them, incline to hold that a state
is bound to give up fugitive criminals, but the majority appear to deny
the obligation as a matter of right, and prefer to put it on the ground
of comity. And the universal practice of nations is to surrender
criminals only in consequence of some special treaty with the country
which demands them.

There are two practical difficulties about extradition which have
probably prevented the growth of any uniform rule on the subject. One is
the variation in the definitions of crime adopted by different
countries. The second is the possibility of the process of extradition
being employed to get hold of a person who is wanted by his country, not
really for a criminal, but for a political offence. In modern states,
and more particularly in England, offences of a political character have
always been carefully excluded from the operation of the law of
extradition.

1. UNITED KINGDOM.--The Extradition Acts 1870-1873 (33 & 34 Vict. cc.
62, and 36 & 37 Vict. c. 60) and the Fugitive Offenders Act 1881 (44 &
45 Vict. c. 69) deal with different branches of the same subject, the
recovery and surrender of fugitive criminals. The Extradition Acts apply
in the case of countries with which Great Britain has extradition
treaties. The Fugitive Offenders Act applies--(1) as between the United
Kingdom and any British possession, (2) as between any two British
possessions, and (3) as between the United Kingdom or a British
possession and certain foreign countries, such as Turkey and China, in
which the crown exercises foreign jurisdiction.

_Conditions of Surrender._--In spite of some earlier authorities it has
long been settled that in English law there is no power to surrender
fugitive criminals to a foreign country without express statutory
authority. Such authority is now given by the Extradition Acts
1870-1873, but only in the case of the offences therein specified, and
with regard to countries with which an arrangement has been entered
into, and to which the acts have been applied by order in council. The
acts are further to be applied, subject to such "conditions, exceptions
and qualifications as may be deemed expedient" (s. 2); and these
conditions, &c., are invariably to be found in the extradition treaty
which is set out in the order in council applying the Extradition Acts
to a particular country. To support a demand for extradition from Great
Britain it is therefore necessary to show that the offence is one of
those enumerated in the Extradition Acts, and also in the particular
treaty, and that the acts charged amount to the offence according to the
laws both of Great Britain and of the state demanding the surrender.

_Surrender of Subjects._--A further question arises where a state is
called on to surrender one of its own subjects. Some of the treaties,
such as those with France and Germany, stipulate that neither
contracting party shall surrender its own subjects, and in such cases a
British subject cannot be surrendered by his own country. The treaties
with Spain, Switzerland and Luxemburg provide for the surrender by Great
Britain of her own subjects, but there is no reciprocity. Other
treaties, such as those with Austria, Belgium, Russia and the
Netherlands, give each party the option of surrendering or refusing to
surrender its own subjects in each particular case. Under such treaties
British subjects are surrendered unless the secretary of state
intervenes to forbid it. Lastly, some treaties, such as that with the
United States, contain no restriction of this kind, and the subjects of
each power are freely surrendered to the other. Surrender by Great
Britain is also subject to the following restrictions contained in s. 3
of the Extradition Act 1870:--(1) that the offence is not of a political
character, and the requisition has not been made with a view to try and
punish for an offence of a political character; (2) that the prisoner
shall not be liable to be tried for any but the specified extradition
offences; (3) that he shall not be surrendered until he has been tried
and served his sentence for offences committed in Great Britain; and (4)
that he shall not be actually given up until fifteen days after his
committal for extradition, so as to allow of an application to the
courts.

_Political Offences._--The question as to what constitutes a political
offence is one of some nicety. It was discussed in _In re Castioni_
(1890, 1 Q.B. 149), where it was held, following the opinion of Mr
Justice Stephen in his _History of the Criminal Law_, that to give an
offence a political character it must be "incidental to and form part of
political disturbances." Extradition was accordingly refused for
homicide committed in the course of an armed rising against the
constituted authorities. In the more recent case of _In re Meunier_
(1894, 2 Q.B. 415), an Anarchist was charged with causing two explosions
in Paris--one at the Café Véry resulting in the death of two persons,
and the other at certain barracks. It was not contended that the outrage
at the cafe was a political crime, but it was argued that the explosion
at the barracks came within the description. The court, however, held
that to constitute a political offence there must be two or more parties
in the state, each seeking to impose a government of its own choice on
the other, which was not the case with regard to Anarchist crimes. The
party of anarchy was the enemy of all governments, and its effects were
directed primarily against the general body of citizens. The test
applied in the earlier case is perhaps the more satisfactory of the two.

With regard to the provision that surrender shall not be granted if the
requisition has in fact been made with a view to try and punish for an
offence of a political character, it, was decided in the case of _Arton_
(1896, 1 Q.B. 108) that a mere suggestion, that after his surrender for
a non-political crime, the prisoner would be interrogated on political
matters (his alleged complicity in the Panama scandal), and punished for
his refusal to answer, was not enough to bring him within the provision.
The court also held that it had no jurisdiction to entertain a
suggestion that the request of the French government for his extradition
was not made in good faith and in the interests of justice.

_Extradition Offences._--The following is a list of crimes in respect of
which extradition may be provided for under the Extradition Acts
1870-1873, and the Slave Trade Act 1873. _Extradition Act_ 1870:--(1)
Murder; (2) Attempt to murder; (3) Conspiracy to murder; (4)
Manslaughter; (5) Counterfeiting and altering money, uttering
counterfeit or altered money; (6) Forgery, counterfeiting, and altering
and uttering what is forged or counterfeited or altered; (7)
Embezzlement and larceny; (8) Obtaining money or goods by false
pretences; (9) Crimes by bankrupts against bankruptcy law; (10) Fraud by
a bailee, banker, agent, factor, trustee or director, or member or
public officer of any company made criminal by any law for the time
being in force; (11) Rape; (12) Abduction; (13) Child-stealing; (14)
Burglary and housebreaking; (15) Arson; (16) Robbery with violence; (17)
Threats by letter or otherwise with intent to extort; (18) Crimes
committed at sea: (a) Piracy by the law of nations; (b) Sinking or
destroying a vessel at sea, or attempting or conspiring to do so; (c)
Assault on a ship on the high seas, with intent to destroy life or to do
grievous bodily harm; (d) Revolt, or conspiring to revolt, by two or
more persons on board a ship on the high seas against the authority of
the master; (19) Bribery. _Extradition Act_ 1873:-(20) Kidnapping and
false imprisonment; (21) Perjury and subornation of perjury. This act
also extends to indictable offences under 24 & 25 Vict. cc. 96, 97, 98,
99, 100, and amending and substituted acts. Among such offences included
in various extradition treaties are the following:--(22) Obtaining
valuable securities by false pretences; (23) Receiving any money,
valuable security or other property, knowing the same to have been
stolen or unlawfully obtained; (24) Falsification of accounts (see _In
re Arton_, 1896, 1 Q.B. 509); (25) Malicious injury to property, if such
offence be indictable;. (26) Knowingly making, without lawful authority,
any instrument, tool or engine adapted and intended for the
counterfeiting of coin of the realm; (27) Abandoning children; exposing
or unlawfully detaining them; (28) Any malicious act done with intent to
endanger the safety of any person in a railway train; (29) Wounding or
inflicting grievous bodily harm; (30) Assault occasioning actual bodily
harm; (31) Assaulting a magistrate or peace or public officer; (32)
Indecent assault; (33) Unlawful carnal knowledge, or any attempt to have
unlawful carnal knowledge, of a girl under age; (34) Bigamy; (35)
Administering drugs or using instruments with intent to procure the
miscarriage of women; (36) Any indictable offence under the laws for the
time being in force in relation to bankruptcy. _Slave Trade Act_ 1873
(36 & 37 Vict. c. 88, s. 27):--(37) Dealing in slaves in such manner as
to constitute a criminal offence against the laws of both states.

The United Kingdom has extradition treaties with practically all
civilized foreign countries; and though it is not practicable to state
which of the statutory extradition offences are included in each, it may
be said generally that crimes 1 to 17 inclusive are covered in all,
though Rumania has reserved the right to refuse, and Portugal does
refuse, to surrender for a crime punishable with death.

The act of 1873 provides for the surrender of accessories before and
after the fact to extradition crimes, and most of the treaties contain a
clause by which extradition is to be granted for participation in any of
the crimes specified in the treaty, provided that such participation is
punishable by the laws of both countries. Several of the treaties also
contain clauses, providing for optional surrender in respect of any
crime not expressly mentioned for which extradition can be granted by
the laws of both countries.

It is further to be noted that the restrictions on surrender in the
Extradition Acts apply only to surrenders by Great Britain. Foreign
countries may surrender fugitives to Great Britain without any treaty,
if they are willing to do so and their law allows of it, and such
surrenders have not infrequently been made. But when surrendered for an
extradition crime, the prisoner cannot be tried in England for any other
crime committed before such surrender, until he has been restored, or
has had an opportunity of returning, to the foreign state from which he
was extradited.

_Procedure._--To obtain from a foreign country the extradition of a
fugitive from the United Kingdom, it is necessary to procure a warrant
for his arrest, and to send it, or a certified copy, to the home
secretary together with such further evidence as is required by the
treaty with the country in question. In most, cases an information or
deposition containing evidence which would justify a committal for trial
in Great Britain will be required. The home secretary will then
communicate through the foreign secretary and the proper diplomatic
channels with the foreign authorities, and in case of urgency will ask
them by telegraph for a provisional arrest. For the arrest in the United
Kingdom of fugitive criminals whose extradition is requested by a
foreign state, two procedures are provided in ss. 7 and 8 of the act of
1870:--(1) On a diplomatic requisition supported by the warrant of
arrest and documentary evidence, the home secretary, if he thinks the
crime is not of a political character, will order the chief magistrate
at Bow Street to proceed; and such magistrate will then issue a warrant
of arrest on such evidence as would be required if the offence had been
committed in the United Kingdom. (2) More summarily, any magistrate or
justice of the peace may issue a provisional warrant of arrest on
evidence which would support such a warrant if the crime had been
committed within his jurisdiction. In practice a sworn information is
required, but this may be based on a telegram from the foreign
authorities. The magistrate or justice must then report the issue of the
warrant to the home secretary, who may cancel it and discharge the
prisoner. When arrested on the provisional warrant, the prisoner will be
brought up before a magistrate and remanded to Bow Street, and will then
be further remanded until the magistrate at Bow Street is notified that
a formal requisition for surrender has been made; and unless such
requisition is made in reasonable time the prisoner is entitled to be
discharged. The examination of the prisoner prior to his committal for
extradition ordinarily takes place at Bow Street. The magistrate is
required to hear evidence that the alleged offence is of a political
character or is not an extradition crime. If satisfied in these
respects, and if the foreign warrant of arrest is duly authenticated,
and evidence is given which according to English law would justify a
committal for trial, if the prisoner has not yet been tried, or would
prove a conviction if he has already been convicted, the magistrate will
commit him for extradition. Under the Extradition Act, 1895 the home
secretary, if of opinion that removal to Bow Street would be dangerous
to the prisoner's life, or prejudicial to his health, may order the case
to be taken by a magistrate at the place where the prisoner was
apprehended, or then is, and the magistrate may order the prisoner to
be detained in such place. After committal for extradition, every
prisoner has fifteen days in which to apply for _habeas corpus_, and
after such period, or at the close of the _habeas corpus_ proceedings if
they are unsuccessful, the home secretary issues his warrant for
surrender, and the prisoner is handed over to the officers of the
foreign government.

The Extradition Acts apply to the British colonies, the governor being
substituted for the secretary of state. Their operation may, however, be
suspended by order in council, as in the case of Canada, where the
colony has passed an Extradition Act of its own (see Statutory Rules and
Orders).

_Fugitive Offenders Act._--There are no extradition treaties with
certain countries in which the crown exercises foreign jurisdiction,
such as Cyprus, Turkey, Egypt, China, Japan, Corea, Zanzibar, Morocco,
Siam, Persia, Somali, &c. In these countries the Fugitive Offenders Act
1881 (44 & 45 Vict. c. 69) has been applied, pursuant to s. 36 of that
statute, and the measures for obtaining surrender of a fugitive criminal
are the same as in a British colony. The act, however, only applies to
persons over whom the crown has jurisdiction in these territories, and
generally is expressly restricted to British subjects.

Under this act a fugitive from one part of the king's dominions to
another, or to a country where the crown exercises foreign jurisdiction,
may be brought back by a procedure analogous to extradition, but
applicable only to treason, piracy and offences punishable with twelve
months' imprisonment with hard labour or more. The original warrant of
arrest must be endorsed by one of several authorities where the
offenders happen to be,--in practice by the home secretary in the United
Kingdom and by the governor in a colony. Pending the arrival of the
original warrant a provisional arrest may be made, as under the
Extradition Acts. The fugitive must then be brought up for examination
before a local magistrate, who, if the endorsed warrant is duly
authenticated, and evidence is produced "which, according to the law
administered by the magistrate, raises a strong or probable presumption
that the offender committed the offence, and that the act applies to
it," may commit him for return. An interval of fifteen days is allowed
for _habeas corpus_ proceedings, and (s. 10) the court has a large
discretion to discharge the prisoner, or impose terms, if it thinks the
case frivolous, or that the return would be unjust or oppressive, or too
severe a punishment. The next step is for the home secretary in the
United Kingdom, and the governor in a colony, to issue a warrant for the
return of the prisoner. He must be removed within a month, in the
absence of reasonable cause to the contrary. If not prosecuted within
six months after arrival, or if acquitted, he is entitled to be sent
back free of cost.

In the case of fugitive offenders from one part of the United Kingdom to
another, it is enough to get the warrant of arrest backed by a
magistrate having jurisdiction in that part of the United Kingdom where
the offender happens to be. A warrant issued by a metropolitan police
magistrate may be executed, without backing, by a metropolitan police
officer anywhere, and there are certain other exceptions, but as a rule
a warrant cannot be executed without being backed by a local magistrate.
     (J. E. P. W.)

2. UNITED STATES.--Foreign extradition is purely an affair of the United
States, and not for the individual states themselves. Upon a demand upon
the United States for extradition, there is a preliminary examination
before a commissioner or judge before there can be a surrender to the
foreign government (Revised Statutes, Title LXVI.; 22 Statutes at Large,
215). It is enough to show probable guilt (_Ornelas_ v. _Ruiz_, 161
United States Reports, 502). An extradition treaty covers crimes
previously committed. If a Power, with which the United States have such
a treaty, surrenders a fugitive charged with a crime not included in the
treaty, he may be tried in the United States for such crime. Inter-state
extradition is regulated by act of Congress under the Constitution of
the United States (Article IV. s. 2; United States Revised Statutes, s.
5278). A surrender may be demanded of one properly charged with an act
which constitutes a crime under the laws of the demanding state,
although it be no crime in the other state. A party improperly
surrendered may be released by writ of _habeas corpus_, either from a
state or United States court (_Robb_ v. _Conolly_, 111 U.S. Reports,
624). On his return to the state from which he fled, he is subject to
prosecution for any crime, though on a foreign extradition the law is
otherwise (_Lascelles_ v. _Georgia_, 148 U.S. Reports, 537).
     (S. E. B.).

  See Sir E. Clarke, _Treatise upon the Law of Extradition_ (4th ed.,
  1904); Biron and Chalmers, _Law and Practice of Extradition_ (1903).

EXTRADOS (_extra_, outside, Fr. _dos_, back), the architectural term for
the outer boundary of the voussoirs of an arch (q.v.).

EXTREME UNCTION, a sacrament of the Roman Catholic Church. In James v.
14 it is ordained that, if any believer is sick, he shall call for the
elders of the church; and they shall pray over him, anointing him with
oil in the name of the Lord; and the prayer of faith shall save him that
is sick, and the Lord shall raise him up; and if he have committed sins,
it shall be forgiven him.

Origen reprobated medical art on the ground that the prescription here
cited is enough; modern faith-healers and Peculiar People have followed
in his wake. The Catholic Church has more wisely left physicians in
possession, and elevated the anointing of the sick into a sacrament to
be used only in cases of mortal sickness, and even then not to the
exclusion of the healing art.

It has been general since the 9th century. The council of Florence A.D.
1439 thus defined it:--

  "The fifth sacrament is extreme unction. Its matter is olive oil,
  blessed by a bishop. It shall not be given except to a sick person
  whose death is apprehended. He shall be anointed in the following
  places: the eyes, ears, nostrils, mouth, hands, feet, reins. The form
  of the sacrament, is this: Through this anointing of thee and through
  its most pious mercy, be forgiven all thy sins of sight, &c. ... and
  so in respect of the other organs. A priest can administer this
  sacrament. But its effect is to make whole the mind, and, so far as it
  is expedient, the body as well."

This sacrament supplements that of penance (viz. remission of
post-baptismal sin) in the sense that any guilt unconfessed or left over
after normal penances imposed by confessors is purged thereby. It was
discussed in the 12th century whether this sacrament is indelible like
baptism, or whether it can be repeated; and the latter view, that of
Peter Lombard, prevailed.

It was a popular opinion in the middle ages that extreme unction
extinguishes all ties and links with this world, so that he who has
received it must, if he recovers, renounce the eating of flesh and
matrimonial relations. A few peasants of Lombardy still believe that one
who has received extreme unction ought to be left to die, and that sick
people may be starved to death through the withholding of food on
superstitious grounds. Such opinions, combated by bishops and councils,
were due to the influence of the _consolamentum_ of the Cathars (q.v.).
In both sacraments the death-bed baptism of an earlier age seems to
survive, and they both fulfil a deep-seated need of the human spirit.

Some Gnostics sprinkled the heads of the dying with oil and water to
render them invisible to the powers of darkness; but in the East
generally, where the need to compete with the Cathar sacrament of
_Consolatio_ was less acutely felt, extreme unction is unknown. The
Latinizing Armenians adopted it from Rome in the crusading epoch. At an
earlier date, however, it was usual to anoint the dead.

In the Roman Church the bishop blesses the oil of the sick used in
extreme unctions on Holy Thursday at the Chrismal Mass,[1] using the
following prayer of the sacramentaries of Gelasius and Hadrian:--

  "Send forth, we pray Thee, O Lord, Thy holy spirit, the Paraclete from
  Heaven, into this fatness of oil, which Thou hast deigned to produce
  from the green wood for refreshment of mind and body; and through Thy
  holy benediction may it be for all that anoint, taste, touch, a
  protection of mind and body, of soul and spirit, unto the easing away
  of all pain, all weakness, all sickness of mind and body; wherefore
  Thou hast anointed priest, kings and prophets and martyrs with thy
  chrism, perfected by Thee, O Lord, blessed and abiding in our bowels
  in the name of our Lord Jesus Christ."

  See L. Duchesne, _Origines du Culte Chrétien_ (Paris, 1898).
       (F. C. C.)

FOOTNOTE:

  [1] The oil left over from the year before is burnt.

EYBESCHÜTZ, JONATHAN (1690-1764), German rabbi, was from 1750 rabbi in
Altona. He was a man of erudition, but he owed his fame chiefly to his
personality. Few men of the period so profoundly impressed their mark on
Jewish life. He became specially notorious because of a curious
controversy that arose concerning the amulets which Eybeschütz was
suspected of issuing. These amulets recognized the Messianic claims of
Sabbatai Sebi (q.v.), and a famous rabbinic contemporary of Eybeschütz,
Jacob Emden, boldly accused him of heresy. The controversy was a
momentous incident in the Jewish life of the period, and though there is
insufficient evidence against Eybeschütz, Emden may be credited with
having crushed the lingering belief in Sabbatai current even in some
orthodox circles.     (I. A.)

EYCK, VAN, the name of a family of Flemish painters in whose works the
rise and mature development of art in western Flanders are represented.
Though bred in the valley of the Meuse, they finally established their
professional domicile in Ghent and in Bruges; and there, by skill and
inventive genius, they changed the traditional habits of the earlier
schools, remodelled the primitive forms of Flemish design, and
introduced a complete revolution into the technical methods of execution
familiar to their countrymen.

1. HUBERT (Huybrecht) VAN EYCK (? 1366-1426) was the oldest and most
remarkable of this race of artists. The date of his birth and the
records of his progress are lost amidst the ruins of the earlier
civilization of the valley of the Meuse. He was born about 1366, at
Maeseyck, under the shelter or protection of a Benedictine convent, in
which art and letters had been cultivated from the beginning of the 8th
century. But after a long series of wars--when the country became
insecure, and the schools which had flourished in the towns decayed--he
wandered to Flanders, and there for the first time gained a name. As
court painter to the hereditary prince of Burgundy, and as client to one
of the richest of the Ghent patricians, Hubert is celebrated. Here, in
middle age, between 1410 and 1420, he signalized himself as the inventor
of a new method of painting. Here he lived in the pay of Philip of
Charolais till 1421. Here he painted pictures for the corporation, whose
chief magistrates honoured him with a state visit in 1424. His principal
masterpiece, the "Worship of the Lamb," commissioned by Jodocus Vijdts,
lord of Pamele, is the noblest creation of the Flemish school, a piece
of which we possess all the parts dispersed from St Bavon in Ghent to
the galleries of Brussels and Berlin,--one upon which Hubert laboured
till he died, leaving it to be completed by his brother. Almost unique
as an illustration of contemporary feeling for Christian art, this great
composition can only be matched by the "Fount of Salvation," in the
museum of Madrid. It represents, on numerous panels, Christ on the
judgment seat, with the Virgin and St John the Baptist at His sides,
hearing the songs of the angels, and contemplated by Adam and Eve, and,
beneath him, the Lamb shedding His blood in the presence of angels,
apostles, prophets, martyrs, knights and hermits. On the outer sides of
the panels are the Virgin and the angel annunciate, the sibyls and
prophets who foretold the coming of the Lord, and the donors in prayer
at the feet of the Baptist and Evangelist. After this great work was
finished it was placed, in 1432, on an altar in St Bavon of Ghent, with
an inscription on the framework describing Hubert as "maior quo nemo
repertus," and setting forth, in colours as imperishable as the picture
itself, that Hubert began and John afterwards brought it to perfection.
John van Eyck certainly wished to guard against an error which
ill-informed posterity showed itself but too prone to foster, the error
that he alone had composed and carried out an altarpiece executed
jointly by Hubert and himself. His contemporaries may be credited with
full knowledge of the truth in this respect, and the facts were equally
well known to the duke of Burgundy or the chiefs of the corporation of
Bruges, who visited the painter's house in state in 1432, and the
members of the chamber of rhetoric at Ghent, who reproduced the Agnus
Dei as a _tableau vivant_ in 1456. Yet a later generation of Flemings
forgot the claims of Hubert, and gave the honours that were his due to
his brother John exclusively.

The solemn grandeur of church art in the 15th century never found, out
of Italy, a nobler exponent than Hubert van Eyck. His representation of
Christ as the judge, between the Virgin and St John, affords a fine
display of realistic truth, combined with pure drawing and gorgeous
colour, and a happy union of earnestness and simplicity with the deepest
religious feeling. In contrast with earlier productions of the Flemish
school, it shows a singular depth of tone and great richness of detail.
Finished with surprising skill, it is executed with the new oil medium,
of which Hubert shared the invention with his brother, but of which no
rival artists at the time possessed the secret,--a medium which consists
of subtle mixtures of oil and varnish applied to the moistening of
pigments after a fashion, only kept secret for a time from gildsmen of
neighbouring cities, but unrevealed to the Italians till near the close
of the 15th century. When Hubert died on the 18th of September 1426 he
was buried in the chapel on the altar of which his masterpiece was
placed. According to a tradition as old as the 16th century, his arm was
preserved as a relic in a casket above the portal of St Bavon of Ghent.
During a life of much apparent activity and surprising successes he
taught the elements of his art to his brother John, who survived him.

2. JOHN (Jan) VAN EYCK (? 1385-1440). The date of his birth is not more
accurately known than that of his elder brother, but he was born much
later than Hubert, who took charge of him and made him his "disciple."
Under this tuition John learnt to draw and paint, and mastered the
properties of colours from Pliny. Later on, Hubert admitted him into
partnership, and both were made court painters to Philip of Charolais.
After the breaking up of the prince's household in 1421, John became his
own master, left the workshop of Hubert, and took an engagement as
painter to John of Bavaria, at that time resident at the Hague as count
of Holland. From the Hague he returned in 1424 to take service with
Philip, now duke of Burgundy, at a salary of 100 livres per annum, and
from that time till his death John van Eyck remained the faithful
servant of his prince, who never treated him otherwise than graciously.
He was frequently employed in missions of trust; and following the
fortunes of a chief who was always in the saddle, he appears for a time
to have been in ceaseless motion, receiving extra pay for secret
services at Leiden, drawing his salary at Bruges, yet settled in a fixed
abode at Lille. In 1428 he joined the embassy sent by Philip the Good to
Lisbon to beg the hand of Isabella of Portugal. His portrait of the
bride fixed the duke's choice. After his return he settled finally at
Bruges, where he married, and his wife bore him a daughter, known in
after years as a nun in the convent of Maeseyck. At the christening of
this child the duke was sponsor, and this was but one, of many
distinctions by which Philip the Good rewarded his painter's merits.
Numerous altarpieces and portraits now give proof of van Eyck's
extensive practice. As finished works of art and models of conscientious
labour they are all worthy of the name they bear, though not of equal
excellence, none being better than those which were completed about
1432. Of an earlier period, a "Consecration of Thomas à Becket" has been
preserved, and may now be seen at Chatsworth, bearing the date of 1421;
no doubt this picture would give a fair representation of van Eyck's
talents at the moment when he started as an independent master, but that
time and accidents of omission and commission have altered its state to
such an extent that no conclusive opinion can be formed respecting it.
The panels of the "Worship of the Lamb" were completed nine years later.
They show that John van Eyck was quite able to work in the spirit of his
brother. He had not only the lines of Hubert's compositions to guide
him, he had also those parts to look at and to study which Hubert had
finished. He continued the work with almost as much vigour as his
master. His own experience had been increased by travel, and he had seen
the finest varieties of landscape in Portugal and the Spanish provinces.
This enabled him to transfer to his pictures the charming scenery of
lands more sunny than those of Flanders, and this he did with accuracy
and not without poetic feeling. We may ascribe much of the success which
attended his efforts to complete the altarpiece of Ghent to the
cleverness with which he [reproduced the varied aspect of changing
scenery, reminiscent here of the orange groves of Cintra, there of the
bluffs and crags of his native valley. In all these backgrounds, though
we miss the scientific rules of perspective with which the van Eycks
were not familiar, we find such delicate perceptions of gradations in
tone, such atmosphere, yet such minuteness and perfection of finish,
that our admiration never flags. Nor is the colour less brilliant or the
touch less firm than in Hubert's panels. John only differs from his
brother in being less masculine and less sternly religious. He excels in
two splendid likenesses of Jodocus Vijdts and his wife Catherine
Burluuts. The same vigorous style and coloured key of harmony
characterizes the small "Virgin and Child" of 1432 at Ince, and the
"Madonna," probably of the same date, at the Louvre, executed for
Rollin, chancellor of Burgundy. Contemporary with these, the male
portraits in the National Gallery, and the "Man with the Pinks," in the
Berlin Museum (1432-1434), show no relaxation of power; but later
creations display no further progress, unless we accept as progress a
more searching delicacy of finish, counterbalanced by an excessive
softness of rounding in flesh contours. An unfaltering minuteness of
hand and great tenderness of treatment may be found, combined with
angularity of drapery and some awkwardness of attitude in the full
length portrait couple (John Arnolfini and his wife) at the National
Gallery (1434), in which a rare insight into the detail of animal nature
is revealed in a study of a terrier dog. A "Madonna with Saints," at
Dresden, equally soft and minute, charms us by the mastery with which an
architectural background is put in. The bold and energetic striving of
earlier days, the strong bright tone, are not equalled by the soft
blending and tender tints of the later ones. Sometimes a crude ruddiness
in flesh strikes us as a growing defect, an instance of which is the
picture in the museum of Bruges, in which Canon van der Paelen is
represented kneeling before the Virgin under the protection of St George
(1434). From first to last van Eyck retains his ability in portraiture.
Fine specimens are the two male likenesses in the gallery of Vienna
(1436), and a female, the master's wife, in the gallery of Bruges
(1439). His death in 1440/41 at Bruges is authentically recorded. He was
buried in St Donat. Like many great artists he formed but few pupils.
Hubert's disciple, Jodocus of Ghent, hardly does honour to his master's
teaching, and only acquires importance after he has thrown off some of
the peculiarities of Flemish teaching. Petrus Cristus, who was taught by
John, remains immeasurably behind him in everything that relates to art.
But if the personal influence of the van Eycks was small, that of their
works was immense, and it is not too much to say that their example,
taken in conjunction with that of van der Weyden, determined the current
and practice of painting throughout the whole of Europe north of the
Alps for nearly a century.

  See also Waagen, _Hubert and Johann van Eyck_ (1822); Voll, _Werke des
  Jan van Eyck_ (1900); L. Kämmerer on the two families in Knackfuss's
  _Künstler-Monographien_ (1898).     (J. A. C.)

EYE, a market-town and municipal borough in the Eye parliamentary
division of Suffolk; England; 94½ m. N.E. from London by the Great
Eastern railway, the terminus of a branch from the Ipswich-Norwich line.
Pop. (1901) 2004. The church of St Peter and St Paul is mainly of
Perpendicular flint work, with Early English portions and a fine
Perpendicular rood screen. It was formerly attached to a Benedictine
priory. Slight fragments of a Norman castle crown a mound of probably
earlier construction. There are a town hall, corn exchange, and grammar
school founded in 1566. Brewing is the chief industry. The town is
governed by a mayor, 4 aldermen and 12 councillors. Area, 4410 acres.

Eye (_Heya_, _Aye_) was once surrounded by a stream, from which it is
said to have derived its name. Leland says it was situated in a marsh
and had formerly been accessible by river vessels from Cromer, though
the river was then only navigable to Burston, 12 m. from Eye. From the
discovery of numerous bones and Roman urns and coins it has been thought
that the place was once the cemetery of a Roman camp. William I. gave
the lordship of Eye to Robert Malet, a Norman, who built a castle and a
Benedictine monastery which was at first subordinate to the abbey of
Bernay in Normandy. Eye is a borough by prescription. In 1205 King John
granted to the townsmen a charter freeing them from various tolls and
customs and from the jurisdiction of the shire and hundred courts. Later
charters were granted by Elizabeth in 1558 and 1574, by James I. in
1604, and by William III. in 1697. In 1574 the borough was newly
incorporated under two bailiffs, ten chief and twenty-four inferior
burgesses, and an annual fair on Whit-Monday and a market on Saturday
were granted. Two members were returned to each parliament from 1571
till 1832, when the Reform Act reduced the membership to one. By the
Redistribution Act of 1885 the representation was merged in the Eye
division of the county. The making of pillow-lace was formerly carried
on extensively, but practically ceased with the introduction of
machinery.

EYE (O. Eng. _eáge_, Ger. _Auge_); derived from an Indo-European root
also seen in Lat. _oc-ulus_, the organ of vision (q.v.).

ANATOMY.--The eye consists of the eyeball, which is the true organ of
sight, as well as of certain muscles which move it, and of the lachrymal
apparatus which keeps the front of it in a moist condition. The
_eyeball_ is contained in the front of the orbit and is a sphere of
about an inch (24 mm.) in diameter. From the front of this a segment of
a lesser sphere projects slightly and forms the _cornea_ (fig. 1, co).
There are three coats to the eyeball, an external (protective), a middle
(vascular), and an internal (sensory). There are also three refracting
media, the aqueous humour, the lens and the vitreous humour or body.

[Illustration: FIG. 1.--Diagrammatic Section through the Eyeball.

  cj, Conjunctiva.             L, Lens.
  co, Cornea.                  V, Vitreous body.
  Sc, Sclerotic.               Z, Zonule of Zinn, the ciliary
  ch, Choroid.                      process being removed to
  pc, Ciliary processes.            show it.
  mc, Ciliary muscle.          p, Canal of Petit.
  O,  Optic nerve.             m, Yellow spot.
  R,  Retina                        The dotted line behind the
  I,  Iris.                         cornea represents its posterior
  aq, Anterior chamber of           epithelium.]
        aqueous humour.

The protective coat consists of the _sclerotic_ in the posterior
five-sixths and the cornea in the anterior sixth. The sclerotic (fig. 1,
Sc) is a firm fibrous coat, forming the "white of the eye," which
posteriorly is pierced by the optic nerve and blends with the sheath of
that nerve, while anteriorly it is continued into the cornea at the
_corneo-scleral junction_. At this point a small canal, known as the
_canal of Schlemm_, runs round the margin of the cornea in the substance
of the sclerotic (see fig. 1). Between the sclerotic and the subjacent
choroid coat is a lymph space traversed by some loose pigmented
connective tissue,--the _lamina fusca_. The cornea is quite continuous
with the sclerotic but has a greater convexity. Under the microscope it
is seen to consist of five layers. Most anteriorly there is a layer of
stratified epithelium, then an anterior elastic layer, then the
_substantia propria_ of the cornea which is fibrous with spaces in which
the stellate _corneal corpuscles_ lie, while behind this is the
posterior elastic layer and then a delicate layer of endothelium. The
transparency of the cornea is due to the fact that all these structures
have the same refractive index.

The middle or vascular coat of the eye consists of the _choroid_, the
_ciliary processes_ and the _iris_. The choroid (fig. 1, ch) does not
come quite as far forward as the corneo-scleral junction: it is composed
of numerous blood-vessels and pigment cells bound together by connective
tissue and, superficially, is lined by a delicate layer of pigmented
connective tissue called the _lamina suprachoroidea_ in contact with the
already-mentioned perichoroidal lymph space. On the deep surface of the
choroid is a structureless basal lamina.

The _ciliary processes_ are some seventy triangular ridges, radially
arranged, with their apices pointing backward (fig. 1, pc), while their
bases are level with the corneo-scleral junction. They are as vascular
as the rest of the choroid, and contain in their interior the _ciliary
muscle_, which consists of radiating and circular fibres. The radiating
fibres (fig. 1, mc) rise, close to the canal of Schlemm, from the margin
of the posterior elastic lamina of the cornea, and pass backward and
outward into the ciliary processes and anterior part of the choroid,
which they pull forward when they contract. The circular fibres lie just
internal to these and are few or wanting in short-sighted people.

The _iris_ (fig. 1, I) is the coloured diaphragm of the eye, the centre
of which is pierced to form the pupil; it is composed of a connective
tissue stroma containing blood-vessels, pigment cells and muscle fibres.
In front of it is a reflection of the same layer of endothelium which
lines the back of the cornea, while behind both it and the ciliary
processes is a double layer of epithelium, deeply pigmented, which
really belongs to the retina. The pigment in the substance of the iris
is variously coloured in different individuals, and is often deposited
after birth, so that, in newly-born European children, the colour of the
eyes is often slate-blue owing to the black pigment at the back of the
iris showing through. White, yellow or reddish-brown pigment is
deposited later in the substance of the iris, causing the appearance,
with the black pigment behind, of grey, hazel or brown eyes. In
blue-eyed people very little interstitial pigment is formed, while in
Albinos the posterior pigment is also absent and the blood vessels give
the pink coloration. The muscle fibres of the iris are described as
circular and radiating, though it is still uncertain whether the latter
are really muscular rather than elastic. On to the front of the iris, at
its margin, the posterior layer of the posterior elastic lamina is
continued as a series of ridges called the _ligamentum pectinatum
iridis_, while between these ridges are depressions known as the _spaces
of Fontana_.

The inner or sensory layer of the wall of the eyeball is the _retina_;
it is a delicate transparent membrane which becomes thinner as the front
of the eye is approached. A short distance behind the ciliary processes
the nervous part of it stops and forms a scalloped border called the
_ora serrata_, but the pigmented layer is continued on behind the
ciliary processes and iris, as has been mentioned, and is known as the
_pars ciliaris retinae_ and _pars iridica retinae_. Under the microscope
the posterior part of the retina is seen to consist of eight layers. In
its passage from the lens and vitreous the light reaches these layers in
the following order:--(1) Layer of nerve fibres; (2) Layer of ganglion
cells; (3) Inner molecular layer; (4) Inner nuclear layer; (5) Outer
molecular layer; (6) Outer nuclear layer; (7) Layer of rods and cones;
(8) Pigmented layer.

  The layer of nerve fibres (fig. 2, 2) is composed of the
  axis-cylinders only of the fibres of the optic nerve which pierce the
  sclerotic, choroid and all the succeeding layers of the retina to
  radiate over its surface.

  The ganglionic layer (fig. 2, 3) consists of a single stratum of large
  ganglion cells, each of which is continuous with a fibre of the
  preceding layer which forms its axon. Each also gives off a number of
  finer processes (dendrites) which arborize in the next layer.

  The inner molecular layer (fig. 2, 4) is formed by the interlacement
  of the dendrites of the last layer with those of the cells of the
  inner nuclear layer which comes next.

  The inner nuclear layer (fig. 2, 5) contains three different kinds of
  cells, but the most important and numerous are large bipolar cells,
  which send one process into the inner molecular layer, as has just
  been mentioned, and the other into the outer molecular layer, where
  they arborize with the ends of the rod and cone fibres.

  The outer molecular layer (fig. 2, 6) is very narrow and is formed by
  the arborizations just described. The outer nuclear layer (fig. 2, 7),
  like the inner, consists of oval cells, which are of two kinds. The
  rod granules are transversely striped, and are connected externally
  with the rods, while internally processes pass into the outer
  molecular layer to end in a knob around which the arborizations of the
  inner nuclear cells lie. The cone granules are situated more
  externally, and are in close contact with the cones; internally their
  processes form a foot-plate in the outer molecular layer from which
  arborizations extend.

  The layer of rods and cones (fig. 2, 9) contains these structures, the
  rods being more numerous than the cones. The rods are spindle-shaped
  bodies, of which the inner segment is thicker than the outer. The
  cones are thicker and shorter than the rods, and resemble Indian
  clubs, the handles of which are directed outward and are transversely
  striped. In the outer part of the rods the visual purple or rhodopsin
  is found.

  The pigmented layer consists of a single layer of hexagonal cells
  containing pigment, which is capable of moving towards the rods and
  cones when the eye is exposed to light and away from them in the dark.

[Illustration: FIG. 2.--Diagrammatic section through the retina to show
the several layers, which are numbered as in the text. Ct, The radial
fibres of the supporting connective tissue.]

Supporting the delicate nervous structures of the retina are a series of
connective tissue rods known as the _fibres of Müller_ (fig. 2, Ct);
these run through the thickness of the retina at right angles to its
surface, and are joined together on the inner side of the layer of nerve
fibres to form the _inner limiting membrane_. More externally, at the
bases of the rods and cones, they unite again to form the outer limiting
membrane.

When the retina is looked at with the naked eye from in front two small
marks are seen on it. One of these is an oval depression about 3 mm.
across, which, owing to the presence of pigment, is of a yellow colour
and is known as the yellow spot (_macula lutea_); it is situated
directly in the antero-posterior axis of the eyeball, and at its margin
the nerve fibre layer is thinned and the ganglionic layer thickened. At
its centre, however, both these layers are wanting, and in the layer of
rods and cones only the cones are present. This central part is called
the _fovea centralis_ and is the point of acutest vision. The second
mark is situated a little below and to the inner side of the yellow
spot; it is a circular disk with raised margins and a depressed centre
and is called the _optic disk_; in structure it is a complete contrast
to the yellow spot, for all the layers except that of the nerve fibres
are wanting, and consequently, as light cannot be appreciated here, it
is known as the "blind spot." It marks the point of entry of the optic
nerve, and at its centre the retinal artery appears and divides into
branches. An appreciation of the condition of the optic disk is one of
the chief objects of the ophthalmoscope.

The _crystalline lens_ (fig. 1, L) with its ligament separates the
aqueous from the vitreous chamber of the eye; it is a biconvex lens the
posterior surface of which is more curved than the anterior. Radiating
from the anterior and posterior poles are three faint lines forming a Y,
the posterior Y being erect and the anterior inverted. Running from
these figures are a series of lamellae, like the layers of an onion,
each of which is made up of a number of fibrils called the lens fibres.
On the anterior surface of the lens is a layer of epithelial cells,
which, towards the margin or equator, gradually elongate into lens
fibres. The whole lens is enclosed in an elastic structureless membrane,
and, like the cornea, its transparency is due to the fact that all its
constituents have the same refractive index.

The ligament of the lens is the thickened anterior part of the hyaloid
membrane which surrounds the vitreous body; it is closely connected to
the iris at the ora serrata, and then splits into two layers, of which
the anterior is the thicker and blends with the anterior part of the
elastic capsule of the lens, so that, when its attachment to the ora
serrata is drawn forward by the ciliary muscle, the lens, by its own
elasticity, increases its convexity. Between the anterior and posterior
splitting of the hyaloid membrane is a circular lymph space surrounding
the margin of the lens known as the _canal of Petit_ (fig. 1, p).

The _aqueous humour_ (fig. 1, aq) is contained between the lens and its
ligament posteriorly and the cornea anteriorly. It is practically a very
weak solution of common salt (chloride of sodium 1.4%). The space
containing it is imperfectly divided into a large anterior and a small
posterior chamber by a perforated diaphragm--the iris.

The _vitreous body_ or _humour_ is a jelly which fills all the contents
of the eyeball behind the lens. It is surrounded by the hyaloid
membrane, already noticed, and anteriorly is concave for the reception
of the lens.

From the centre of the optic disk to the posterior pole of the lens a
lymph canal formed by a tube of the hyaloid membrane stretches through
the centre of the vitreous body; this is the _canal of Stilling_, which
in the embryo transmitted the hyaloid artery to the lens. The
composition of the vitreous is practically the same as that of the
aqueous humour.

The _arteries of the eyeball_ are all derived from the ophthalmic branch
of the internal carotid, and consist of the retinal which enters the
optic nerve far back in the orbit, the two long ciliaries, which run
forward in the choroid and join the anterior ciliaries, from muscular
branches of the ophthalmic, in the circulus iridis major round the
margin of the iris, and the six to twelve short ciliaries which pierce
the sclerotic round the optic nerve and supply the choroid and ciliary
processes.

The _veins of the eyeball_ emerge as four or five trunks rather behind
the equator; these are called from their appearance _venae vorticosae_,
and open into the superior ophthalmic vein. In addition to these there
is a retinal vein which accompanies its artery.

_Accessory Structures of the Eye._--The _eyelids_ are composed of the
following structures from in front backward: (1) Skin; (2) Superficial
fascia; (3) Orbicularis palpebrarum muscle; (4) _Tarsal plates_ of
fibrous tissue attached to the orbital margin by the superior and
inferior _palpebral ligaments_, and, at the junction of the eyelids, by
the external and internal _tarsal ligaments_ of which the latter is also
known as the _tendo oculi_; (5) _Meibomian glands_, which are large
modified sebaceous glands lubricating the edges of the lids and
preventing them adhering, and _Glands of Moll_, large sweat glands
which, when inflamed, cause a "sty"; (6) the _conjunctiva_, a layer of
mucous membrane which lines the back of the eyelids and is reflected on
to the front of the globe, the reflection forming the fornix: on the
front of the cornea the conjunctiva is continuous with the layer of
epithelial cells already mentioned.

The _lachrymal_ gland is found in the upper and outer part of the front
of the orbit. It is about the size of an almond and has an upper
(orbital) and a lower (palpebral) part. Its six to twelve ducts open on
to the superior fornix of the conjunctiva.

The _lachrymal canals_ (canaliculi) (see fig. 3, 2 and 3) are superior
and inferior, and open by minute orifices (puncta) on to the free
margins of the two eyelids near their inner point of junction. They
collect the tears, secreted by the lachrymal gland, which thus pass
right across the front of the eyeball, continually moistening the
conjunctiva. The two ducts are bent round a small pink tubercle called
the _caruncula lachrymalis_ (fig. 3, 4) at the inner angle of the
eyelids, and open into the _lachrymal sac_ (fig. 3, 5), which lies in a
groove in the lachrymal bone. The sac is continued down into the _nasal
duct_ (fig. 3, 6), which is about ¾ inch long and opens into the
inferior meatus of the nose, its opening being guarded by a valve.

[Illustration: FIG. 3.--Lachrymal Canals and Duct.

  1, Orbicular muscle.    5, Lachrymal sac.
  2, Lachrymal canal.     6, Lachrymal duct.
  3, Punctum.             7, Angular artery.
  4, Caruncula.]

The orbit contains seven muscles, six of which rise close to the optic
foramen. The _levator palpebrae superioris_ is the highest, and passes
forward to the superior tarsal plate and fornix of the conjunctiva. The
_superior_ and _inferior recti_ are inserted into the upper and lower
surfaces of the eyeball respectively; they make the eye look inward as
well as up or down. The external and internal recti are inserted into
the sides of the eyeball and make it look outward or inward. The
superior oblique runs forward to a pulley in the inner and front part of
the roof of the orbit, round which it turns to be inserted into the
outer and back part of the eyeball. It turns the glance downward and
outward. The inferior oblique rises from the inner and front part of the
floor of the orbit, and is also inserted into the outer and back part of
the eyeball. It directs the glance upward and outward. Of all these
muscles the superior oblique is supplied by the fourth cranial nerve,
the external rectus by the sixth and the rest by the third.

The posterior part of the eyeball and the anterior parts of the muscles
are enveloped in a lymph space, known as the _capsule of Tenon_, which
assists their movements.

    FIG. 4.                         FIG. 5.

  Diagram of Developing           Diagram of Developing
    Eye (1st stage).                Eye (2nd stage).
  [alpha], Forebrain.             [beta], Optic cup.
  [beta], Optic vesicle.          [delta], Invagination of lens.
  [gamma], Superficial ectoderm.    Other letters as in fig. 4.]
  [delta], Thickening for lens.

EMBRYOLOGY.--As is pointed out in the article BRAIN, the _optic
vesicles_ grow out from the fore-brain, and the part nearest the brain
becomes constricted and elongated to form the optic stalk (see figs. 4
and 5, [beta]). At the same time the ectoderm covering the side of the
head thickens and becomes invaginated to form the lens vesicle (see
figs. 4 and 5, [delta]), which later loses its connexion with the
surface and approaches the optic vesicle, causing that structure to
become cupped for its reception, so that what was the optic vesicle
becomes the optic cup and consists of an external and an internal layer
of cells (fig. 6 [beta] and [delta]). Of these the outer cells become
the retinal pigment, while the inner form the other layers of the
retina. The invagination of the optic cup extends, as the _choroidal
fissure_ (not shown in the diagrams), along the lower and back part of
the optic stalk, and into this slit sinks some of the surrounding
mesoderm to form the vitreous body and the hyaloid arteries, one of
which persists.[1] When this has happened the fissure closes up. The
anterior epithelium of the lens vesicle remains, but from the posterior
the lens fibres are developed and these gradually fill up the cavity.
The superficial layer of head ectoderm, from which the lens has been
invaginated and separated, becomes the anterior epithelium of the
cornea (fig. 6, [epsilon]), and between it and the lens the mesoderm
sinks in to form the cornea, iris and anterior chamber of the eye, while
surrounding the optic cup the mesoderm forms the sclerotic and choroid
coats (fig. 7, [eta] and [zeta]). Up to the seventh month the pupil is
closed by the _membrana pupillaris_, derived from the capsule of the
lens which is part of the mesodermal ingrowth through the choroidal
fissure already mentioned. The hyaloid artery remains, as a prolongation
of the retinal artery to the lens, until just before birth, but after
that its sheath forms the canal of Stilling. Most of the fibres of the
optic nerve are centripetal and begin as the axons of the ganglionic
cells of the retina; a few, however, are centrifugal and come from the
nerve cells in the brain.

[Illustration: FIG. 6.

  Diagram of Developing Eye (3rd stage).

  [delta], Solid lens.
  [epsilon], Corneal epithelium.