Chapter I: Part 1

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Transcriber's notes:

(1) Numbers following letters (without space) like C2 were originally
printed in subscript. Letter subscripts are preceded by an
underscore, like C_n.

(2) Characters following a carat (^) were printed in superscript.

(3) Side-notes were relocated to function as titles of their respective
paragraphs.

(4) Macrons and breves above letters and dots below letters were not
inserted.

(5) [root] stands for the root symbol; [alpha], [beta], etc. for greek
letters.

(6) The following typographical errors have been corrected:

ARTICLE GAUDEN, JOHN: "... and on the fact that it was admitted by
Clarendon, who should have had means of being acquainted with the
truth." 'should' amended from 'sould'.

ARTICLE GAWAIN: "In the later Historia of Geoffrey of Monmouth, and
its French translation by Wace, Gawain plays an important and
'pseudo-historic' rôle." 'Geoffrey' amended from 'Goeffrey'.

ARTICLE GAYA: "... and at which a religious fair is held each
September, attended by 10,000 to 20,000 pilgrims." '20,000' amended
from '20,0000'.

ARTICLE GECKO: "The arrangement of the lamellae and pads differs
much in the various genera and is used for classificatory
purposes." 'classificatory' amended from 'classificactory'.

ARTICLE GEDDES, ALEXANDER: "Although under ecclesiastical censures,
he had never swerved from a consistent profession of faith as a
Catholic; and on his death-bed he duly received the last rites of
his communion." 'Although' amended from 'Athough'.

ARTICLE GELSEMIUM: "It was first described in 1640 by John
Parkinson, who grew it in his garden from seed sent by Tradescant
from Virginia; at the present time it is but rarely seen, even in
botanical gardens, in Great Britain." 'Britain' amended from
'Britian'.

ARTICLE GEM: "From the Byzantine period downward one peculiarity of
gem-engraving becomes noticeable." 'peculiarity' amended from
'peculiarty'.

ARTICLE GENEALOGY: "... or that Bilhan points to an old clan
associated with Reuben (Gen. xxxv. 22) or Edom (Bilhan, Gen. xxxvi.
27), ..." 'Bilhan' amended from 'Bilhah'.

ARTICLE GENTIANACEAE: "... bright blue corolla, is visited by
bumble bees; and G. verna, with a still longer narrower tube, is
visited by Lepidoptera." 'bumble' amended from 'humble'.

ARTICLE GENTZ, FRIEDRICH VON: "... but partly supplemented in
Österreichs Teilnahme an den Befreiungskriegen (Vienna, 1887) ..."
'Österreichs' amended from 'Öesterreichs'.

ENCYCLOPAEDIA BRITANNICA

A DICTIONARY OF ARTS, SCIENCES, LITERATURE
AND GENERAL INFORMATION

ELEVENTH EDITION

VOLUME XI, SLICE V

Gassendi, Pierre to Geocentric

ARTICLES IN THIS SLICE:

GASSENDI, PIERRE GEFLE
GASTEIN GEGENBAUR, CARL
GASTRIC ULCER GEGENSCHEIN
GASTRITIS GEIBEL, EMANUEL
GASTROPODA GEIGE
GASTROTRICHA GEIGER, ABRAHAM
GATAKER, THOMAS GEIJER, ERIK GUSTAF
GATCHINA GEIKIE, SIR ARCHIBALD
GATE GEIKIE, JAMES
GATEHOUSE GEIKIE, WALTER
GATES, HORATIO GEILER VON KAISERSBERG, JOHANN
GATESHEAD GEINITZ, HANS BRUNO
GATH GEISHA
GATLING, RICHARD JORDAN GEISLINGEN
GATTY, MARGARET GEISSLER, HEINRICH
GAU, JOHN GELA
GAUDEN, JOHN GELADA
GAUDICHAUD-BEAUPRÉ, CHARLES GELASIUS
GAUDRY, JEAN ALBERT GELATI
GAUDY GELATIN
GAUERMANN, FRIEDRICH GELDERLAND (duchy)
GAUGE GELDERLAND (province of Holland)
GAUHATI GELDERN
GAUL, GILBERT WILLIAM GELL, SIR WILLIAM
GAUL GELLERT, CHRISTIAN FÜRCHTEGOTT
GAULT GELLERT
GAUNTLET GELLIUS, AULUS
GAUR (ruined city of India) GELLIVARA
GAUR (wild ox) GELNHAUSEN
GAUSS, KARL FRIEDRICH GELO
GAUSSEN, FRANÇOIS SAMUEL LOUIS GELSEMIUM
GAUTIER, ÉMILE THÉODORE LÉON GELSENKIRCHEN
GAUTIER, THÉOPHILE GEM
GAUTIER D'ARRAS GEM, ARTIFICIAL
GAUZE GEMBLOUX
GAVARNI GEMINI
GAVAZZI, ALESSANDRO GEMINIANI, FRANCESCO
GAVELKIND GEMISTUS PLETHO, GEORGIUS
GAVESTON, PIERS GEMMI PASS
GAVOTTE GENDARMERIE
GAWAIN GENEALOGY
GAWLER GENELLI, GIOVANNI BUONAVENTURA
GAY, JOHN GENERAL
GAY, MARIE FRANÇOISE SOPHIE GENERATION
GAY, WALTER GENESIS
GAYA GENET
GAYAL GENEVA (New York, U.S.A.)
GAYANGOS Y ARCE, PASCUAL DE GENEVA (Switzerland)
GAYARRÉ, CHARLES ÉTIENNE ARTHUR GENEVA CONVENTION
GAY-LUSSAC, JOSEPH LOUIS GENEVA, LAKE OF
GAZA, THEODORUS GENEVIÈVE, ST
GAZA GENEVIÈVE, OF BRABANT
GAZALAND GENGA, GIROLAMO
GAZEBO GENISTA
GAZETTE GENIUS
GEAR GENUS, STÉPHANIE DE SAINT-AUBIN
GEBER GENNA
GEBHARD TRUCHSESS VON WALDBURG GENNADIUS II.
GEBWEILER GENOA
GECKO GENOVESI, ANTONIO
GED, WILLIAM GENSONNÉ, ARMAND
GEDDES, ALEXANDER GENTIAN
GEDDES, ANDREW GENTIANACEAE
GEDDES, JAMES LORRAINE GENTILE
GEDDES, SIR WILLIAM DUGUID GENTILE DA FABRIANO
GEDYMIN GENTILESCHI, ARTEMISIA and ORAZIO DE'
GEE, THOMAS GENTILI, ALBERICO
GEEL, JACOB GENTLE
GEELONG GENTLEMAN
GEESTEMÜNDE GENTZ, FRIEDRICH VON
GEFFCKEN, FRIEDRICH HEINRICH GEOCENTRIC
GEFFROY, MATHIEU AUGUSTE

GASSENDI[1] [GASSEND], PIERRE (1592-1655), French philosopher, scientist and mathematician, was born of poor parents at Champtercier, near Digne, in Provence, on the 22nd of January 1592. At a very early age he gave indications of remarkable mental powers and was sent to the college at Digne. He showed particular aptitude for languages and mathematics, and it is said that at the age of sixteen he was invited to lecture on rhetoric at the college. Soon afterwards he entered the university of Aix, to study philosophy under P. Fesaye. In 1612 he was called to the college of Digne to lecture on theology. Four years later he received the degree of doctor of theology at Avignon, and in 1617 he took holy orders. In the same year he was called to the chair of philosophy at Aix, and seems gradually to have withdrawn from theology. He lectured principally on the Aristotelian philosophy, conforming as far as possible to the orthodox methods. At the same time, however, he followed with interest the discoveries of Galileo and Kepler, and became more and more dissatisfied with the Peripatetic system. It was the period of revolt against the Aristotelianism of the schools, and Gassendi shared to the full the empirical tendencies of the age. He, too, began to draw up objections to the Aristotelian philosophy, but did not at first venture to publish them. In 1624, however, after he had left Aix for a canonry at Grenoble, he printed the first part of his _Exercitationes paradoxicae adversus Aristoteleos_. A fragment of the second book was published later at La Haye (1659), but the remaining five were never composed, Gassendi apparently thinking that after the _Discussiones Peripateticae_ of Francesco Patrizzi little field was left for his labours.

After 1628 Gassendi travelled in Flanders and Holland. During this time he wrote, at the instance of Mersenne, his examination of the mystical philosophy of Robert Fludd (_Epistolica dissertatio in qua praecipua principia philosophiae Ro. Fluddi deteguntur_, 1631), an essay on parhelia (_Epistola de parheliis_), and some valuable observations on the transit of Mercury which had been foretold by Kepler. He returned to France in 1631, and two years later became provost of the cathedral church at Digne. Some years were then spent in travelling through Provence with the duke of Angoulême, governor of the department. The only literary work of this period is the _Life of Peiresc_, which has been frequently reprinted, and was translated into English. In 1642 he was engaged by Mersenne in controversy with Descartes. His objections to the fundamental propositions of Descartes were published in 1642; they appear as the fifth in the series contained in the works of Descartes. In these objections Gassendi's tendency towards the empirical school of speculation appears more pronounced than in any of his other writings. In 1645 he accepted the chair of mathematics in the Collège Royal at Paris, and lectured for many years with great success. In addition to controversial writings on physical questions, there appeared during this period the first of the works by which he is known in the history of philosophy. In 1647 he published the treatise _De vita, moribus, et doctrina Epicuri libri octo_. The work was well received, and two years later appeared his commentary on the tenth book of Diogenes Laërtius, _De vita, moribus, et placitis Epicuri, seu Animadversiones in X. librum Diog. Laër_. (Lyons, 1649; last edition, 1675). In the same year the more important _Syntagma philosophiae Epicuri_ (Lyons, 1649; Amsterdam, 1684) was published.

In 1648 ill-health compelled him to give up his lectures at the Collège Royal. He travelled in the south of France, spending nearly two years at Toulon, the climate of which suited him. In 1653 he returned to Paris and resumed his literary work, publishing in that year lives of Copernicus and Tycho Brahe. The disease from which he suffered, lung complaint, had, however, established a firm hold on him. His strength gradually failed, and he died at Paris on the 24th of October 1655. A bronze statue of him was erected by subscription at Digne in 1852.

His collected works, of which the most important is the _Syntagma philosophicum_ (_Opera_, i. and ii.), were published in 1658 by Montmort (6 vols., Lyons). Another edition, also in 6 folio volumes, was published by N. Averanius in 1727. The first two are occupied entirely with his _Syntagma philosophicum_; the third contains his critical writings on Epicurus, Aristotle, Descartes, Fludd and Lord Herbert, with some occasional pieces on certain problems of physics; the fourth, his _Institutio astronomica_, and his _Commentarii de rebus celestibus_; the fifth, his commentary on the tenth book of Diogenes Laërtius, the biographies of Epicurus, N.C.F. de Peiresc, Tycho Brahe, Copernicus, Georg von Peuerbach, and Regiomontanus, with some tracts on the value of ancient money, on the Roman calendar, and on the theory of music, to all which is appended a large and prolix piece entitled _Notitia ecclesiae Diniensis_; the sixth volume contains his correspondence. The _Lives_, especially those of Copernicus, Tycho and Peiresc, have been justly admired. That of Peiresc has been repeatedly printed; it has also been translated into English. Gassendi was one of the first after the revival of letters who treated the _literature_ of philosophy in a lively way. His writings of this kind, though too laudatory and somewhat diffuse, have great merit; they abound in those anecdotal details, natural yet not obvious reflections, and vivacious turns of thought, which made Gibbon style him, with some extravagance certainly, though it was true enough up to Gassendi's time--"le meilleur philosophe des littérateurs, et le meilleur littérateur des philosophes."

Gassendi holds an honourable place in the history of physical science.
He certainly added little to the stock of human knowledge, but the
clearness of his exposition and the manner in which he, like Bacon,
urged the importance of experimental research, were of inestimable
service to the cause of science. To what extent any place can be
assigned him in the history of philosophy is more doubtful. The
_Exercitationes_ on the whole seem to have excited more attention than
they deserved. They contain little or nothing beyond what had been
already advanced against Aristotle. The first book expounds clearly,
and with much vigour, the evil effects of the blind acceptance of the
Aristotelian dicta on physical and philosophical study; but, as is the
case with so many of the anti-Aristotelian works of this period, the
objections show the usual ignorance of Aristotle's own writings. The
second book, which contains the review of Aristotle's dialectic or
logic, is throughout Ramist in tone and method. The objections to
Descartes--one of which at least, through Descartes's statement of it
in the appendix of objections in the _Meditationes_ has become
famous--have no speculative value, and in general are the outcome of
the crudest empiricism. His labours on Epicurus have a certain
historical value, but the want of consistency inherent in the
philosophical system raised on Epicureanism is such as to deprive it
of genuine worth. Along with strong expressions of empiricism we find
him holding doctrines absolutely irreconcilable with empiricism in any
form. For while he maintains constantly his favourite maxim "that
there is nothing in the intellect which has not been in the senses"
(_nihil in intellectu quod non prius fuerit in sensu_), while he
contends that the imaginative faculty (_phantasia_) is the counterpart
of sense--that, as it has to do with material images, it is itself,
like sense, material, and essentially the same both in men and brutes;
he at the same time admits that the intellect, which he affirms to be
immaterial and immortal--the most characteristic distinction of
humanity--attains notions and truths of which no effort of sensation
or imagination can give us the slightest apprehension (Op. ii. 383).
He instances the capacity of forming "general notions"; the very
conception of universality itself (_ib._ 384), to which he says
brutes, who partake as truly as men in the faculty called _phantasia_,
never attain; the notion of God, whom he says we may imagine to be
corporeal, but understand to be incorporeal; and lastly, the reflex
action by which the mind makes its own phenomena and operations the
objects of attention.

The _Syntagma philosophicum_, in fact, is one of those eclectic
systems which unite, or rather place in juxtaposition, irreconcilable
dogmas from various schools of thought. It is divided, according to
the usual fashion of the Epicureans, into logic (which, with Gassendi
as with Epicurus, is truly _canonic_), physics and ethics. The logic,
which contains at least one praiseworthy portion, a sketch of the
history of the science, is divided into theory of right apprehension
(_bene imaginari_), theory of right judgment (_bene proponere_),
theory of right inference (_bene colligere_), theory of right method
(_bene ordinare_). The first part contains the specially empirical
positions which Gassendi afterwards neglects or leaves out of account.
The senses, the sole source of knowledge, are supposed to yield us
immediately cognition of individual things; phantasy (which Gassendi
takes to be material in nature) reproduces these ideas; understanding
compares these ideas, which are particular, and frames general ideas.
Nevertheless, he at the same time admits that the senses yield
knowledge--not of things--but of qualities only, and holds that we
arrive at the idea of thing or substance by induction. He holds that
the true method of research is the analytic, rising from lower to
higher notions; yet he sees clearly, and admits, that inductive
reasoning, as conceived by Bacon, rests on a general proposition not
itself proved by induction. He ought to hold, and in disputing with
Descartes he did apparently hold, that the evidence of the senses is
the only convincing evidence; yet he maintains, and from his special
mathematical training it was natural he should maintain, that the
evidence of reason is absolutely satisfactory. The whole doctrine of
judgment, syllogism and method is a mixture of Aristotelian and Ramist
notions.

In the second part of the _Syntagma_, the physics, there is more that
deserves attention; but here, too, appears in the most glaring manner
the inner contradiction between Gassendi's fundamental principles.
While approving of the Epicurean physics, he rejects altogether the
Epicurean negation of God and particular providence. He states the
various proofs for the existence of an immaterial, infinite, supreme
Being, asserts that this Being is the author of the visible universe,
and strongly defends the doctrine of the foreknowledge and particular
providence of God. At the same time he holds, in opposition to
Epicureanism, the doctrine of an immaterial rational soul, endowed
with immortality and capable of free determination. It is altogether
impossible to assent to the supposition of Lange (_Gesch. des
Materialismus_, 3rd ed., i. 233), that all this portion of Gassendi's
system contains nothing of his own opinions, but is introduced solely
from motives of self-defence. The positive exposition of atomism has
much that is attractive, but the hypothesis of the _calor vitalis_
(vital heat), a species of _anima mundi_ (world-soul) which is
introduced as physical explanation of physical phenomena, does not
seem to throw much light on the special problems which it is invoked
to solve. Nor is his theory of the weight essential to atoms as being
due to an inner force impelling them to motion in any way reconcilable
with his general doctrine of mechanical causes.

In the third part, the ethics, over and above the discussion on
freedom, which on the whole is indefinite, there is little beyond a
milder statement of the Epicurean moral code. The final end of life is
happiness, and happiness is harmony of soul and body (_tranquillitas
animi et indolentia corporis_). Probably, Gassendi thinks, perfect
happiness is not attainable in this life, but it may be in the life to
come.

The _Syntagma_ is thus an essentially unsystematic work, and clearly
exhibits the main characteristics of Gassendi's genius. He was
critical rather than constructive, widely read and trained thoroughly
both in languages and in science, but deficient in speculative power
and original force. Even in the department of natural science he shows
the same inability steadfastly to retain principles and to work from
them; he wavers between the systems of Brahe and Copernicus. That his
revival of Epicureanism had an important influence on the general
thinking of the 17th century may be admitted; that it has any real
importance in the history of philosophy cannot be granted.

AUTHORITIES.--Gassendi's life is given by Sorbière in the first
collected edition of the works, by Bugerel, _Vie de Gassendi_ (1737;
2nd ed., 1770), and by Damiron, _Mémoire sur Gassendi_ (1839). An
abridgment of his philosophy was given by his friend, the celebrated
traveller, Bernier (_Abrégé de la philosophie de Gassendi_, 8 vols.,
1678; 2nd ed., 7 vols., 1684). The most complete surveys of his work
are those of G.S. Brett (_Philosophy of Gassendi_, London, 1908),
Buhle (_Geschichte der neuern Philosophie_, iii. 1, 87-222), Damiron
(_Mémoires pour servir à l'histoire de philosophie au XVII^e siècle_),
and P.F. Thomas (_La Philosophie de Gassendi_, Paris, 1889). See also
Ritter, _Geschichte der Philosophie_, x. 543-571; Feuerbach, _Gesch.
d. neu. Phil. von Bacon bis Spinoza_, 127-150; F.X. Kiefl, _P.
Gassendis Erkenntnistheorie und seine Stellung zum Materialismus_
(1893) and "Gassendi's Skepticismus" in _Philos. Jahrb._ vi. (1893);
C. Güttler, "Gassend oder Gassendi?" in _Archiv f. Gesch. d. Philos._
x. (1897), pp. 238-242. (R. Ad.; X.)

FOOTNOTE:

[1] It was formerly thought that _Gassendi_ was really the genitive
of the Latin form _Gassendus_. C. Güttler, however, holds that it is
a modernized form of the O. Fr. _Gassendy_ (see paper quoted in
bibliography).

GASTEIN, in the duchy of Salzburg, Austria, a side valley of the Pongau or Upper Salzach, about 25 m. long and 1¼ m. broad, renowned for its mineral springs. It has an elevation of between 3000 and 3500 ft. Behind it, to the S., tower the mountains Mallnitz or Nassfeld-Tauern (7907 ft.) and Ankogel (10,673 ft.), and from the right and left of these mountains two smaller ranges run northwards forming its two side walls. The river Ache traverses the valley, and near Wildbad-Gastein forms two magnificent waterfalls, the upper, the Kesselfall (196 ft.), and the lower, the Bärenfall (296 ft.). Near these falls is the Schleierfall (250 ft.), formed by the stream which drains the Bockhart-see. The valley is also traversed by the so-called Tauern railway (opened up to Wildbad-Gastein in September 1905), which goes to Mallnitz, piercing the Tauern range by a tunnel 9260 yds. in length. The principal villages of the valley are Hof-Gastein, Wildbad-Gastein and Böckstein.

HOF-GASTEIN, pop. (1900) 840, the capital of the valley, is also a watering-place, the thermal waters being conveyed here from Wildbad-Gastein by a conduit 5 m. long, constructed in 1828 by the emperor Francis I. of Austria. Hof-Gastein was, after Salzburg, the richest place in the duchy, owing to its gold and silver mines, which were already worked during the Roman period. During the 16th century these mines were yielding annually 1180 lb. of gold and 9500 lb. of silver, but since the 17th century they have been much neglected and many of them are now covered by glaciers.

WILDBAD-GASTEIN, commonly called _Bad-Gastein_, one of the most celebrated watering-places in Europe, is picturesquely situated in the narrow valley of the Gasteiner Ache, at an altitude of 3480 ft. The thermal springs, which issue from the granite mountains, have a temperature of 77°-120° F., and yield about 880,000 gallons of water daily. The water contains only 0.35 to 1000 of mineral ingredients and is used for bathing purposes. The springs are resorted to in cases of nervous affections, senile and general debility, skin diseases, gout and rheumatism. Wildbad-Gastein is annually visited by over 8500 guests. The springs were known as early as the 7th century, but first came into fame by a successful visit paid to them by Duke Frederick of Austria in 1436. Gastein was a favourite resort of William I. of Prussia and of the Austrian imperial family, and it was here that, on the 14th of August 1865, was signed the agreement known as the Gastein Convention, which by dividing the administration of the conquered provinces of Schleswig and Holstein between Austria and Prussia postponed for a while the outbreak of war between the two powers. It was also here (August-September 1879) that Prince Bismarck negotiated with Count Julius Andrássy the Austro-German treaty, which resulted in the formation of the Triple Alliance.

See Pröll, _Gastein, Its Springs and Climate_ (Vienna, 5th ed., 1893).

GASTRIC ULCER (ulcer of the stomach), a disease of much gravity, commonest in females, and especially in anaemic domestic servants. It is connected in many instances with impairment of the circulation in the stomach and the formation of a clot in a small blood-vessel (thrombosis). It may be due to an impoverished state of the blood (anaemia), but it may also arise from disease of the blood-vessels, the result of long-continued indigestion and gastric catarrh.

When clotting takes place in a blood-vessel the nutrition of that limited area of the stomach is cut off, and the patch undergoes digestion by the unresisted action of the gastric juices, an ulcer being formed. The ulcer is usually of the size of a silver threepence or sixpence, round or oval, and, eating deeply, is apt to make a hole right through the coats of the stomach. Its usual site is upon the posterior wall of the upper curvature, near to the pyloric orifice. It may undergo a healing process at any stage, in which case it may leave but little trace of its existence; while, on the other hand, it may in the course of cicatrizing produce such an amount of contraction as to lead to stricture of the pylorus, or to a peculiar hour-glass deformity of the stomach. Perforation is in most cases quickly fatal, unless previously the stomach has become adherent to some neighbouring organ, by which the dangerous effects of this occurrence may be averted, or unless the condition has been promptly recognized and an operation has been quickly done. Usually there is but one ulcer, but sometimes there are several ulcers.

The symptoms of ulcer of the stomach are often indefinite and obscure, and in some cases the diagnosis has been first made on the occurrence of a fatal perforation. First among the symptoms is pain, which is present at all times, but is markedly increased after food. The pain is situated either at the lower end of the breast-bone or about the middle of the back. Sometimes it is felt in the sides. It is often extremely severe, and is usually accompanied with localized tenderness and also with a sense of oppression, and by an inability to wear tight clothing. The pain is due to the movements of the stomach set up by the presence of the food, as well as to the irritation of the inflamed nerve filaments in the floor of the ulcer. Vomiting is a usual symptom. It occurs either soon after the food is swallowed or at a later period, and generally relieves the pain and discomfort. Vomiting of blood (haematemesis) is a frequent and important symptom. The blood may show itself in the form of a brown or coffee-like mixture, or as pure blood of dark colour and containing clots. It comes from some vessel or vessels which the ulcerative process has ruptured. Blood is also found mixed with the discharges from the bowels, rendering them dark or tarry-looking. The general condition of the patient with gastric ulcer is, as a rule, that of extreme ill-health, with pallor, emaciation and debility. The tongue is red, and there is usually constipation. In most of the cases the disease is chronic, lasting for months or years; and in those cases where the ulcers are large or multiple, incomplete healing may take place, relapses occurring from time to time. But the ulcers may give rise to no marked symptoms, and there have been instances where fatal perforation suddenly took place, and where post-mortem examination revealed the existence of long-standing ulcers which had given rise to no suggestive symptoms. While gastric ulcer is to be regarded as dangerous, its termination, in the great majority of cases, is in recovery. It frequently, however, leaves the stomach in a delicate condition, necessitating the utmost care as regards diet. Occasionally the disease proves fatal by sudden haemorrhage, but a fatal result is more frequently due to perforation and the escape of the contents of the stomach into the peritoneal cavity, in which case death usually occurs in from twelve to forty-eight hours, either from shock or from peritonitis. Should the stomach become adherent to another organ, and fatal perforation be thus prevented, chronic "indigestion" may persist, owing to interference with the natural movements of the stomach. Stricture of the pylorus and consequent dilatation of the stomach may be caused by the cicatrization of an ulcer.

The patient should at once be sent to bed and kept there, and allowed for a while nothing stronger than milk and water or milk and lime water. But if bleeding has recently taken place no food whatever should be allowed by the stomach, and the feeding should be by nutrient enemata. As the symptoms quiet down, eggs may be given beaten up with milk, and later, bread and milk and home-made broths and soups. Thus the diet advances to chicken and vegetables rubbed through a sieve, to custard pudding and bread and butter. As regards medicines, iron is the most useful, but no pills of any sort should be given. Under the influence of rest and diet most gastric ulcers get well. The presence of healthy-looking scars upon the surface of the stomach, which are constantly found in operating upon the interior of the abdomen, or as revealed in post-mortem examinations, are evidence of the truth of this statement. It is unlikely that under the treatment just described perforation of the stomach will take place, and if the surgeon is called in to assist he will probably advise that operation is inadvisable. Moreover, he knows that if he should open the abdomen to search for an ulcer of the stomach he might fail to find it; more than that, his search might also be in vain if he opened the stomach itself and examined the interior. Serious haemorrhages, however, may make it necessary that a prompt and thorough search should be made in order that the surgeon may endeavour to locate the ulcer, and, having found it, secure the damaged vessel and save the patient from death by bleeding.

Perforation of a gastric ulcer having taken place, the septic germs, which were harmless whilst in the stomach, escape with the rest of the contents of the stomach into the general peritoneal cavity. The immediate effects of this leakage are sudden and severe pain in the upper part of the abdomen and a great shock to the system (collapse). The muscles of the abdominal wall become hard and resisting, and as peritonitis appears and the intestines are distended with gas, the abdomen is distended and becomes greatly increased in size and ceases to move, the respiratory movements being short and quick. At first, most likely, the temperature drops below normal, and the pulse quickens. Later, the temperature rises. If nothing is done, death from the septic poisoning of peritonitis is almost certain.

The treatment of ruptured gastric ulcer demands immediate operation. An incision should be made in the upper part of the middle line of the abdomen, and the perforation should be looked for. There is not, as a rule, much difficulty in finding it, as there are generally deposits of lymph near the spot, and other signs of local inflammation; moreover, the contents of the stomach may be seen escaping from the opening. The ulcer is to be closed by running a "purse-string" suture in the healthy tissue around it, and the place is then buried in the stomach by picking up small folds of the stomach-wall above and below it and fixing them together by suturing. This being done, the surface of the stomach, and the neighbouring viscera which have been soiled by the leakage, are wiped clean and the abdominal wound is closed, provision being made for efficient drainage. A large proportion of cases of perforated gastric ulcer thus treated recover. (E. O.*)

GASTRITIS (Gr. [Greek: gastêr], stomach), an inflammatory affection of the stomach, of which the condition of catarrh, or irritation of its mucous membrane, is the most frequent and most readily recognized. This may exist in an acute or a chronic form, and depends upon some condition, either local or general, which produces a congested state of the circulation in the walls of the stomach (see DIGESTIVE ORGANS: _Pathology_).

_Acute Gastritis_ may arise from various causes. The most intense forms of inflammation of the stomach are the toxic conditions which follow the swallowing of corrosive poisons, such as strong mineral acids of alkalis which may extensively destroy the mucous membrane. Other non-corrosive poisons cause acute degeneration of the stomach wall (see POISONS). Acute inflammatory conditions may be secondary to zymotic diseases such as diphtheria, pyaemia, typhus fever and others. Gastritis is also caused by the ingestion of food which has begun to decompose, or may result from eating unsuitable articles which themselves remain undigested and so excite acute catarrhal conditions. These give rise to the symptoms well known as characterizing an acute "bilious attack," consisting in loss of appetite, sickness or nausea, and headache, frontal or occipital, often accompanied with giddiness. The tongue is furred, the breath foetid, and there is pain or discomfort in the region of the stomach, with sour eructations, and frequently vomiting, first of food and then of bilious matter. An attack of this kind tends to subside in a few days, especially if the exciting cause be removed. Sometimes, however, the symptoms recur with such frequency as to lead to the more serious chronic form of the disease.

The treatment bears reference, in the first place, to any known source of irritation, which, if it exist, may be expelled by an emetic or purgative (except in cases due to poisoning). This, however, is seldom necessary, since vomiting is usually present. For the relief of sickness and pain the sucking of ice and counter-irritation over the region of the stomach are of service. Further, remedies which exercise a soothing effect upon an irritable mucous membrane, such as bismuth or weak alkaline fluids, and along with these the use of a light milk diet, are usually sufficient to remove the symptoms.

_Chronic Gastric Catarrh_ may result from the acute or may arise independently. It is not infrequently connected with antecedent disease in other organs, such as the lungs, heart, liver or kidneys, and it is especially common in persons addicted to alcoholic excess. In this form the texture of the stomach is more altered than in the acute form, except in the toxic and febrile forms above referred to. It is permanently in a state of congestion, and its mucous membrane and muscular coat undergo thickening and other changes, which markedly affect the function of digestion. The symptoms are those of dyspepsia in an aggravated form (see DYSPEPSIA), of which discomfort and pain after food, with distension and frequently vomiting, are the chief; and the treatment must be conducted in reference to the causes giving rise to it. The careful regulation of the diet, alike as to the amount, the quality, and the intervals between meals, demands special attention. Feeding on artificially soured milk may in many cases be useful. Lavage or washing out of the stomach with weak alkaline solutions has been used with marked success in the treatment of chronic gastritis. Of medicinal agents, bismuth, arsenic, nux vomica, and the mineral acids are all of acknowledged efficacy, as are also preparations of pepsin.

GASTROPODA, the second of the five classes of animals constituting the phylum Mollusca. For a discussion of the relationship of the Gastropoda to the remaining classes of the phylum, see MOLLUSCA.

The Gastropoda are mainly characterized by a loss of symmetry,
produced by torsion of the visceral sac. This torsion may be resolved
into two successive movements. The first is a ventral flexure in the
antero-posterior or sagittal plane; the result of this is to
approximate the two ends of the alimentary canal. In development, the
openings of the mantle-cavity and the anus are always originally
posterior; later they are brought forward ventrally. During this first
movement flexure is also produced by the coiling of the visceral sac
and shell; primitively the latter was bowl-shaped; but the ventral
flexure, which brings together the two extremities of the digestive
tube, gives the visceral sac the outline of a more or less acute cone.
The shell necessarily takes this form also, and then becomes coiled in
a dorsal or anterior plane--that is to say, it becomes exogastric.
This condition may be seen in embryonic _Patellidae, Fissurellidae_
and _Trochidae_ (fig. 1, A), and agrees with the method of coiling of
a mollusc without lateral torsion, such as _Nautilus_. But ultimately
the coil becomes ventral or endogastric, in consequence of the second
torsion movement then apparent.

FIG. 1.--Three stages in the development of Trochus, during the
process of torsion. (After Robert.)

A, Nearly symmetrical larva (veliger).
B, A stage 1½ hours later than A.
C, A stage 3½ hours later than B.
f, Foot.
op, Operculum.
pac, Pallial cavity.
ve, Velum.]

The shell is represented as fixed, while the head and foot rotate from
left to right. In reality the head and foot are fixed and the shell
rotates from right to left.

The second movement is a lateral torsion of the visceral mass, the
foot remaining a fixed point; this torsion occurs in a plane
approximately at right angles to that of the first movement, and
carries the pallial aperture and the anus from behind forwards. If, at
this moment, the animal were placed with mouth and ventral surface
turned towards the observer, this torsion carries the circumanal
complex in a clockwise direction (along the right side in dextral
forms) through 180° as compared with its primitive condition. The
(primitively) right-hand organs of the complex thus become left-hand,
and vice versa. The visceral commissure, while still surrounding the
digestive tract, becomes looped; its right half, with its proper
ganglion, passes to the left side over the dorsal face of the
alimentary canal (whence the name supra-intestinal), while the left
half passes below towards the right side, thus originating the name
infra-intestinal given to this half and to its ganglion. Next, the
shell, the coil of which was at first exogastric, being also included
in this rotation through 180°, exhibits an endogastric coiling (fig.
1, B, C). This, however, is not generally retained in one plane, and
the spire projects, little by little, on the side which was originally
left, but finally becomes right (in dextral forms, with a clockwise
direction, if viewed from the side of the spire; but counter-clockwise
in sinistral forms). Finally, the original symmetry of the circumanal
complex vanishes; the anus leaves the centre of the pallial cavity and
passes towards the right side (left side in sinistral forms); the
organs of this side become atrophied and disappear. The essential
feature of the asymmetry of Gastropoda is the atrophy or disappearance
of the primitively left half of the circumanal complex (the right half
in sinistral forms), including the gill, the auricle, the osphradium,
the hypobranchial gland and the kidney.

In dextral Gastropods the only structure found on the topographically
right side of the rectum is the genital duct. But this is not part of
the primitive complex. It is absent in the most primitive and
symmetrical forms, such as _Haliotis_ and _Pleurotomaria_. Originally
the gonads opened into the kidneys. In the most primitive existing
Gastropods the gonad opens into the right kidney (_Patellidae,
Trochidae, Fissurellidae_). The gonaduct, therefore, is derived from
the topographically right kidney. The transformation has been
actually shown to take place in the development of Paludina. In a
dextral Gastropod the shell is coiled in a right-handed spiral from
apex to mouth, and the spiral also projects to the right of the median
plane of the animal.

FIG. 2.--Four stages in the development of a Gastropod showing the
process of body torsion. (After Robert.)

A, Embryo without flexure.
B, Embryo with ventral flexure of the intestine.
C, Embryo with ventral flexure and exogastric shell.
D, Embryo with lateral torsion and an endogastric shell.
a, Anus.
f, Foot.
m, Mouth.
pa, Mantle.
pac, Pallial cavity.
ve, Velum.]

When the shell is sinistral the asymmetry of the organs is usually
reversed, and there is a complete situs _inversus viscerum_, the
direction of the spiral of the shell corresponding to the position of
the organs of the body. _Triforis, Physa, Clausilia_ are examples
of sinistral Gastropods, but reversal also occurs as an individual
variation among forms normally dextral. But there are forms in which
the involution is "hyperstrophic," that is to say, the turns of the
spire projecting but slightly, the spire, after flattening out
gradually, finally becomes re-entrant and transformed into a false
umbilicus; at the same time that part which corresponds to the
umbilicus of forms with a normal coil projects and constitutes a false
spire; the coil thus appears to be sinistral, although the asymmetry
remains dextral, and the coil of the operculum (always the opposite to
that of the shell) sinistral (e.g. _Lanistes_ among Streptoneura,
_Limacinidae_ among Opisthobranchia). The same, _mutatis mutandis_,
may occur in sinistral shells.

A, Unrotated ancestral condition.
B, Quarter-rotation.
C, Complete semi-rotation (the limit).
an, Anus.
ln, rn, Primarily left nephridium and primarily right nephridium.
lvg, Primarily left (subsequently the sub-intestinal) visceral
ganglion.
rvg, Primarily right (subsequently the sub-intestinal) visceral
ganglion.
cerg, Cerebral ganglion.
plg, Pleural ganglion.
pedg, Pedal ganglion.
abg, Abdominal ganglion.
bucc, Buccal mass.
W, Wooden arc representing the base-line of the wall of the visceral
hump.
x, 'x, Pins fastening the elastic cord (representing the visceral
nerve loop) to W.]

The problem of the causes of the torsion of the Gastropod body has
been much discussed. E.R. Lankester in the ninth edition of this work
attributed it to the pressure of the shell and visceral hump towards
the right side. He referred also to the nautiloid shell of the larva
falling to one side. But these are two distinct processes. In the
larva a nautiloid shell is developed which is coiled exogastrically,
that is, dorsally, and the pallial cavity is posterior or ventral
(fig. 2, C): the larva therefore resembles _Nautilus_ in the relations
of body and shell. The shell then rotates towards the left side
through 180°, so that it becomes ventral or endogastric (fig. 2, D).
The pallial cavity, with its organs, is by this torsion moved up the
_right_ side of the larva to the dorsal surface, and thus the left
organs become right and vice versa. In the subsequent growth of the
shell the spire comes to project on the right side, which was
originally the left. Neither the rotation of the shell as a whole nor
its helicoid spiral coiling is the immediate cause of the torsion of
the body in the individual, for the direction of the torsion is
indicated in the segmentation of the ovum, in which there is a
complete reversal of the cleavage planes in sinistral as compared
with dextral forms. The facts, however, strongly suggest that the
original cause of the torsion was the weight of the exogastric shell
and visceral hump, which in an animal creeping on its ventral surface
necessarily fell over to one side. It is not certain that the
projection of the spire to the originally left side of the shell has
anything to do with the falling over of the shell to that side. The
facts do not support such a suggestion. In the larva there is no
projection at the time the torsion takes place. In some forms the
coiling disappears in the adult, leaving the shell simply conical as
in _Patellidae, Fissurellidae_, &c., and in some cases the shell is
coiled in one plane, e.g. _Planorbis_. In all these cases the torsion
and asymmetry of the body are unaffected.

The characteristic torsion attains its maximum effect among the
majority of the Streptoneura. It is followed in some specialized
Heteropoda and in the Euthyneura by a torsion in the opposite
direction, or detorsion, which brings the anus farther back and
untwists the visceral commissure (see Euthyneura, below). This
conclusion has shown that the Euthyneura do not represent an archaic
form of Gastropoda, but are themselves derived from streptoneurous
forms. The difference between the two sub-classes has been shown to be
slight; certain of the more archaic Tectibranchia (_Actaeon_) and
Pulmonata (_Chilina_) still have the visceral commissure long and not
untwisted. The fact that all the Euthyneura are hermaphrodite is not a
fundamental difference; several Streptoneura are so, likewise
_Valvata, Oncidiopsis, Marsenina, Odostomia, Bathysciadium,
Entoconcha_.

_Classification._--The class Gastropoda is subdivided as follows:

Sub-class I. Streptoneura.
Order 1. Aspidobranchia.
Sub-order 1. Docoglossa.
" 2. Rhipidoglossa.
Order 2. Pectinibranchia.
Sub-order 1. Taenioglossa.
Tribe 1. Platypoda.
" 2. Heteropoda.
Sub-order 2. Stenoglossa.
Tribe 1. Rachiglossa.
" 2. Toxiglossa.

Sub-class II. Euthyneura.
Order 1. Opisthobranchia.
Sub-order 1. Tectibranchia.
Tribe 1. Bullomorpha.
" 2. Aplysiomorpha.
" 3. Pleurobranchomorpha.
Sub-order 2. Nudibranchia.
Tribe 1. Tritoniomorpha.
" 2. Doridomorpha.
" 3. Eolidomorpha.
" 4. Elysiomorpha.
Order 2. Pulmonata.
Sub-order 1. Basommatophora.
" 2. Stylommatophora.
Tribe 1. Holognatha.
" 2. Agnatha.
" 3. Elasmognatha.
" 4. Ditremata.

Sub-Class I.--STREPTONEURA

In this division the torsion of the visceral mass and visceral commissure is at its maximum, the latter being twisted into a figure of eight. The right half of the commissure with its ganglion is supra-intestinal, the left half with its ganglion infra-intestinal. In some cases each pleural ganglion is connected with the opposite branch of the visceral commissure by anastomosis with the pallial nerve, a condition which is called dialyneury; or there may be a direct connective from the pleural ganglion to the visceral ganglion of the opposite side, which is called zygoneury. The head bears only one pair of tentacles. The radular teeth are of several different kinds in each transverse row. The heart is usually posterior to the branchia (proso-branchiate). The sexes are usually separate.

The old division into Zygobranchia and Azygobranchia must be abandoned, for the Azygobranchiate Rhipidoglossa have much greater affinity to the Zygobranchiate _Haliotidae_ and _Fissurellidae_ than to the Azygobranchia in general. This is shown by the labial commissure and pedal cords of the nervous system, by the opening of the gonad into the right kidney, and by other points. Further, the _Pleurotomariidae_ have been discovered to possess two branchiae. The sub-class is now divided into two orders: the Aspidobranchia in which the branchia or ctenidium is bipectinate and attached only at its base, and the Pectinibranchia in which the ctenidium is monopectinate and attached to the mantle throughout its length.

x, y, The median antero-posterior axis.
a, Cephalic tentacle.
b, Plantar surface of the foot.
c, Free edge of the shell.
d, The branchial efferent vessel carrying aerated blood to the
auricle, and here interrupting the circlet of gill lamellae.
e, Margin of the mantle-skirt.
f, Gill lamellae (_not_ ctenidia, but special pallial growths,
comparable with those of Pleurophyllidia).
g, The branchial efferent vessel.
h, Factor of the branchial advehent vessel.
i, Interspaces between the muscular bundles of the root of the foot,
causing the separate areae seen in fig. 5, c.]

Order I. ASPIDOBRANCHIA.--These are the most primitive Gastropods,
retaining to a great degree the original symmetry of the organs of the
pallial complex, having two kidneys, in some cases two branchiae, and
two auricles. The gonad has no accessory organs and except in
_Neritidae_ no duct, but discharges into the right kidney.

c, Muscular bundles forming the root of the foot, and adherent to
the shell.
e, Free mantle-skirt.
em, Tentaculiferous margin of the same.
i, Smaller (left) nephridium.
k, Larger (right) nephridium.
l, Pericardium.
lx, Fibrous septum, behind the pericardium.
n, Liver.
int, Intestine.
ecr, Anterior area of the mantle-skirt over-hanging the head
(cephalic hood).]

Forms adapted to terrestrial life and to aerial respiration occur in
various divisions of Gastropods, and do not constitute a single
homogeneous group. Thus the _Helicinidae_, which are terrestrial, are
now placed among the Aspidobranchia. In these there are neither
branchia nor osphradium, and the pallial chamber which retains its
large opening serves as a lung. Degeneration of the shell occurs in
some members of the order. It is largely covered by the mantle in some
_Fissurellidae_, is entirely internal in _Pupilia_ and absent in
_Titiscaniidae_.

The common limpet is a specially interesting and abundant example of
the more primitive Aspidobranchia. The foot of the limpet is a nearly
circular disk of muscular tissue; in front, projecting from and raised
above it, are the head and neck (figs. 4, 13). The visceral hump forms
a low conical dome above the sub-circular foot, and standing out all
round the base of this dome so as completely to overlap the head and
foot, is the circular mantle-skirt. The depth of free mantle-skirt is
greatest in front, where the head and neck are covered in by it. Upon
the surface of the visceral dome, and extending to the edge of the
free mantle-skirt, is the conical shell. When the shell is taken away
(best effected by immersion in hot water) the surface of the visceral
dome is found to be covered by a black-coloured epithelium, which may
be removed, enabling the observer to note the position of some organs
lying below the transparent integument (fig. 5). The muscular columns
(c) attaching the foot to the shell form a ring incomplete in front,
external to which is the free mantle-skirt. The limits of the large
area formed by the flap over the head and neck (ecr) can be traced,
and we note the anal papilla showing through and opening on the right
shoulder, so to speak, of the animal into the large anterior region of
the sub-pallial space. Close to this the small renal organ (i, mediad)
and the larger renal organ (k, to the right and posteriorly) are seen,
also the pericardium (l) and a coil of the intestine (int) embedded
in the compact liver.

a, Cephalic tentacle.
b, Foot.
c, Muscular substance forming the root of the foot.
d, The capito-pedal organs of Lankester (= rudimentary ctenidia).
e, Mantle-skirt.
f, Papilla of the larger nephridium.
g, Anus.
h, Papilla of the smaller nephridium.
i, Smaller nephridium.
k, Larger nephridium.
l, Pericardium.
m, Cut edge of the mantle-skirt.
n, Liver.
p, Snout.]

On cutting away the anterior part of the mantle-skirt so as to expose
the sub-pallial chamber in the region of the neck, we find the right
and left renal papillae (discovered by Lankester in 1867) on either
side of the anal papilla (fig. 6), but no gills. If a similar
examination be made of the allied genus _Fissurella_ (fig. 17, d), we
find right and left of the two renal apertures a right and left
gill-plume or ctenidium, which here as in _Haliotis_ and
_Pleurotomaria_ retain their original paired condition. In _Patella_
no such plumes exist, but right and left of the neck are seen a pair
of minute oblong yellow bodies (fig. 6, d), which were originally
described by Lankester as orifices possibly connected with the
evacuation of the generative products. On account of their position
they were termed by him the "capito-pedal orifices," being placed near
the junction of head and foot. J.W. Spengel has, however, in a most
ingenious way shown that these bodies are the representatives of the
typical pair of ctenidia, here reduced to a mere rudiment. Near to
each rudimentary ctenidium Spengel has discovered an olfactory patch
or osphradium (consisting of modified epithelium) and an olfactory
nerve-ganglion (fig. 8). It will be remembered that, according to
Spengel, the osphradium of mollusca is definitely and intimately
related to the gill-plume or ctenidium, being always placed near the
base of that organ; further, Spengel has shown that the nerve-supply
of this olfactory organ is always derived from the visceral loop.
Accordingly, the nerve-supply affords a means of testing the
conclusion that we have in Lankester's capito-pedal bodies the
rudimentary ctenidia. The accompanying diagrams (figs. 9, 10) of the
nervous systems of _Patella_ and of _Haliotis_, as determined by
Spengel, show the identity in the origin of the nerves passing from
the visceral loop to Spengel's olfactory ganglion of the Limpet, and
that of the nerves which pass from the visceral loop of _Haliotis_ to
the olfactory patch or osphradium, which lies in immediate relation on
the right and on the left side to the right and left gill-plumes
(ctenidia) respectively. The same diagrams serve to demonstrate the
streptoneurous condition of the visceral loop in Aspidobranchia.

Thus, then, we find that the limpet possesses a symmetrically disposed
pair of ctenidia in a rudimentary condition, and justifies its
position among Aspidobranchia. At the same time it possesses a
totally distinct series of _functional_ gills, which are not derived
from the modification of the typical molluscan ctenidium. These gills
are in the form of delicate lamellae (fig. 4, f), which form a series
extending completely round the inner face of the depending
mantle-skirt. This circlet of gill-lamellae led Cuvier to class the
limpets as Cyclobranchiata, and, by erroneous identification of them
with the series of metamerically repeated ctenidia of _Chiton_, to
associate the latter mollusc with the former. The gill-lamellae of
_Patella_ are processes of the mantle comparable with the plait-like
folds often observed on the roof of the branchial chamber in other
Gastropoda (e.g. _Buccinum_ and _Haliotis_). They are termed pallial
gills. The only other molluscs in which they are exactly represented
are the curious Opisthobranchs _Phyllidia_ and _Pleurophyllidia_ (fig.
55). In these, as in _Patella_, the typical ctenidia are aborted, and
the branchial function is assumed by close-set lamelliform processes
arranged in a series beneath the mantle-skirt on either side of the
foot. In fig. 4, d, the large branchial vein of _Patella_ bringing
blood from the gill-series to the heart is seen; where it crosses the
series of lamellae there is a short interval devoid of lamellae.

B, Surface view of a rudimentary ctenidium of _Patella_ excised and
viewed as a transparent object. (Lankester.)]

ce, Cerebral ganglia.
c'e, Cerebral commissure.
pl, Pleural ganglion.
pe, Pedal ganglion. p'e, Pedal nerve.
s, s', Nerves (right and left) to the mantle.
o, Olfactory ganglion, connected by nerve to the streptoneurous
visceral loop.]

The heart in _Patella_ consists of a single auricle (not two as in
_Haliotis_ and _Fissurella_) and a ventricle; the former receives the
blood from the branchial vein, the latter distributes it through a
large aorta which soon leads into irregular blood-lacunae.

The existence of two renal organs in _Patella_, and their relation to
the pericardium (a portion of the coelom), is important. Each renal
organ is a sac lined with glandular epithelium (ciliated cell, with
concretions) communicating with the exterior by its papilla, and by a
narrow passage with the pericardium. The connexion with the
pericardium of the smaller of the two renal organs was demonstrated by
Lankester in 1867, at a time when the fact that the renal organ of the
Mollusca, as a rule, opens into the pericardium, and is therefore a
typical nephridium, was not known. Subsequent investigations carried
on under the direction of the same naturalist have shown that the
larger as well as the smaller renal sac is in communication with the
pericardium. The walls of the renal sacs are deeply plaited and thrown
into ridges. Below the surface these walls are excavated with
blood-vessels, so that the sac is practically a series of
blood-vessels covered with renal epithelium, and forming a meshwork
within a space communicating with the exterior. The larger renal sac
(remarkably enough, that which is aborted in other Anisopleura)
extends between the liver and the integument of the visceral dome very
widely. It also bends round the liver as shown in fig. 12, and forms
a large sac on half of the upper surface of the muscular mass of the
foot. Here it lies close upon the genital body (ovary or testis), and
in such intimate relationship with it that, when ripe, the gonad
bursts into the renal sac, and its products are carried to the
exterior by the papilla on the right side of the anus (Robin, Dall).
This fact led Cuvier erroneously to the belief that a duct existed
leading from the gonad to this papilla. The position of the gonad,
best seen in the diagrammatic section (fig. 13), is, as in other
Aspidobranchia, devoid of a special duct communicating with the
exterior. This condition, probably an archaic one, distinguishes the
Aspidobranchia from other Gastropoda.

ce, Cerebral ganglion.
pl.pe, The fused pleural and pedal ganglia.
pe, The right pedal nerve.
ce.pl, The cerebro-pleural connective.
ce.pe, The cerebro-pedal connective.
s, s', Right and left mantle nerves.
ab, Abdominal ganglion or site of same.
o, o, Right and left olfactory ganglia and osphardia receiving nerve
from visceral loop.]

pl, Pallial nerve.
p, Pedal nerve.
A, Abdominal ganglia in the streptoneurous visceral commissure, with
supra- and sub-intestine ganglion on each side.
B, Buccal ganglia.
C, C, Cerebral ganglia.
es, Cerebral commissure.
o, Otocysts attached to the cerebro-pedal connectives.]

f, Papilla of the larger nephridium.
g, Anal papilla with rectum leading from it.
h, Papilla of the smaller nephridium, which is only represented by
dotted outlines.
l, Pericardium indicated by a dotted outline--at its right side are
seen the two reno-pericardial pores.
ff, The sub-anal tract of the large nephridium given off near its
papilla and seen through the unshaded smaller nephridium.
ks.a, Anterior superior lobe of the large nephridium.
ks.l, Left lobe of same.
ks.p, Posterior lobe of same.
ks.i, Inferior sub-visceral lobe of same.]