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• . . •• ■

C.P. EDINBURGH L

R27049.

BRARY

0236

INTRODUCTION

TO THE

COMPARATIVE ANATOMY

ANIMALS ;

COMPILED WITH CONSTANT REFERENCE TO PHYSIOLOGY,

AND

ELUCIDATED BY TWENTY COPPER-PLATES :

C. G. CARUS, Med. et Phil. Doct.

PROFESSOR OF MIDWIFERY TO THE MEDICO-CHIRURGICAL ACADEMY AT DRESDEN,
DIRECTOR OF THE ROYAL SAXON OBSTETRICAL INSTITUTION AT
THE SAME PLACE, AND ASSOCIATE OF VARIOUS

LEARNED SOCIETIES. . >

TRANSLATED FROM THE GERMAN, BYf

* -vt •y

R. T. GORE, "

MEMBER 01 THE ROYAL COLLEGE OF SURGEONS IN LONDON.

k-9

typ^i

•/

IN TWO VOLUMES VOL. II.

LONDON:

LONGMAN, KF.ES, ORME, BROWN, AND GREEN,
TATER-NOSTER-ROW.

1827

PRINTED BY RICHARD CRUTTWELL,
ST. J A ME.s’s-STREET, BATH.

TABLE OF CONTENTS.

VOL. II.

PAGE

PART II.

History of Organs belonging to the Vegetative Sphere 1

BOOK I.

History of the Organs subservient to Individual Reproduction 2

Chapter I. Organs of Digestion ...» ib.

I. In Animals without Spinal Marrow and Brain ib.

Section I. Zoophytes ib.

II. Mollusca 6

A. Acephala ib.

B. Gasteropoda 8

C. Cephalopoda 11

III. Articulata 13

A. Vermes ib.

B. Crustacea 17

C. Insecta 20

A. Organs of Mastication and

Suction in Insects 22

B. Intestinal Canal in Insects ... 24

C. Of the Termination of the In-

testinal Canal in Insects ... 32

II. In Animals with Brain and Spinal Marrow 35

Section I. Fishes ib.

A. Organs of Mastication, Taste, Suction,

and Deglutition ib.

B. (Esophagus and Stomach 4-1

C. Intestine •. 44

Section II. Amphibia 48

A. Organs of Mastication, Taste, and

Deglutition ib.

B. CEsophagus and Stomach 55

C. Intestine 57

III. Birds 58

A. Organs of Mastication, Taste, Suction,

and Deglutition ib.

B. CEsophagus and Stomach 64

C. Intestine 68

IV. Mammalia 72

A. Organs of Mastication, Taste, Suction,

and Deglutition ib.

B. CEsophagus and Stomach 89

C. Intestine 100

Chapter II. Organs of Respiration and Secretion Ill

I. Of the different Forms of the Cutaneous Organ 112

Section I. In Zoophytes ib.

II. In Molluscs 115

III. In Articulata 117

IV. In Fishes 123

V. In Amphibia 125

VI. In Birds 129

VII. In Mammalia 133

II. Of the various Forms of the Respiratory Organs 141

A. Respiration of Animals without Spinal Marrow and

Brain 142

Section I. Zoophytes ib.

IL Mollusca • »•••• ••••••••••••• »• • rt-( •••••••«• 145

A. Acephala ib.

B. Gasteropoda 150

C. Cephalopoda 152

III. Articulata 154

A. Vermes ib.

B. Crustacea 157

C. Insecta 158

B. Respiration of Animals with Brain and Spinal Marrow 168

Section I. Fishes ib.

II. Respiratory andVoeal Organs of Amphibia 179

A. Batrachia 181

B. Chelonia 185

C. Qphidia 187

D. Sauria - 189

Section III. Respiratory and Vocal Organs of Birds 190
IV. Respiratory and Vocal Organs of Mam-
malia 197

III. Of the different Forms of Repetition of the Respiratory

Organs ; or, Of the Secretory Organs 209

A. Repetition of the Respiratory Organs in the Digestive

System ; or. Of the peculiar Organs of Secretion

belonging to the Intestinal Canal ib ,

Section I. Salivary Organs , 211

1. In Zoophytes ib ,

2. In Mollusca ib,

3. In Articulata 212

4. In Fishes 215

- 5. In Amphibia ib,

6. In Birds 216

7. In Mammalia 217

II. Of some other Secretions poured into

the Intestinal Canal in the remaining
parts of its course, in the higher Classes
of Animals . 219

III. Of the Organs secreting Bile 222

A. In Animals without Vertebrae ib,

1. In Zoophytes ib,

2. In Mollusca ib,

3. In Articulata 225

B. In Vertebral Animals 229

1. In Fishes 230

2. In Amphibia 232

3. In Birds 234

4. In Mammalia 236

IV. Of the Pancreas 238

1. In Amphibia 240

2. In Birds ib,

3. In Mammalia 241

B. Repetition of the Respiratory Organs in the Sexual

System ; or, Of the Urinary Organs 242

Section I. In Fishes 244

II. In Amphibia 246

III. In Birds 251

IV. In Mammalia 254

C. Of Secretions in or near the Respiratory Organs

themselves 257

D. Of tlu' Thymus ami Thyroid in the superior Cla«os

of Animals . ^7*8

Cbaptkr 111. Of the Vascular System -t*3

A. In Animals without Spinal Marrow ami Brain ... 2t>l
Section 1. In Zoophytes

II. In Mollusea 2(*7

A. Acephala A.

B. Gasteropoda 2t>3

C. Ceplui)o|Hxla -71

III. In Artieulata 272

A. Vermes ib.

11. Crustacea 274

C. Inseeta 275

11. In Animals with Spinal Marrow ami Brain 27 r

Section l. In Fishes t?7i>

(a.J Blood- Vessels A.

b.' Lymphatics 2S2

11. In Amphibia 283

(a ) Blood-Vessels ib.

(b. ) Lymphatics 280

III. In Birds 201

t <i. > Blood-l essels ib.

fb.J Lymphatics 201

IV. In Mammalia 20a

a. ) Blood-Vessels A.

lb. Lymphatics 300

BOOR II.

History of the Organs subservient to the Reproduction of the Species ;

and also. Of tlie Developement of individual Animal Organisms 302

Cuaftkk 1. Of the Sexual Organs 3rH*

A. In Animals without Spinal Marrow and Brain A.

Section 1. Zoophytes A.

II. Mollusea 30S

(a.) Acephala ib.

lb. Gastetopoda 311

fc.J Cephalopoda 314

111. Artieulata 31t»

(a.) Venues 317

(b.j Cnistaoea .. 310

(c.j Inseeta 320

Vll

J3. In Animals with Spinal Marrow and Brain 326

Section I. Fishes ib.

II. Amphibia 330

III. Birds 334«

IV. Mammalia 337

(a.) Female Organs ib.

(b.J Male Organs 346

(c.J Secretions connected with the

Sexual Functions 353

Chapter II. Of the Developement of the individual Organism in the

different Classes of Animals 356

Section I. Zoophytes 360

II. Mollusca 361

III. Articulatu 364

IV. Fishes 367

V. Amphibia 369

VI. Birds 374.

VII. Mammdlia 380

APPENDIX I. A few Observations on the Dissection and Prepa-
ration of the Bodies of Animals 389

II. Discovery of a Circulation in Insects 392

‘

1 • " • •

PART II.

HISTORY OF ORGANS BELONGING TO THE
VEGETATIVE SPHERE.

§.432. JLHE reasons (§. 49.) which appeared to justify
us, when treating of the superior animal structures, in
separating them into two series of formations, do not
operate to the same extent as regards the organs of the
Vegetative Sphere; for though in the higher species of
animals there is no want of distinct gradation in the vascu-
lar system, the characteristic member of this sphere, yet,
it is not such as to establish a difference between inferior
and superior species equally decided with that dependent
on the appearance of a Spinal Marrow, Brain, and Skele-
ton : nay, the perfection of even the human frame is here
less absolutely recognizeable ; and consequently, nothing
hinders that we should trace the developement of the
Systems belonging to this Sphere in a continuous series
from the Polype to Man.

As 1 conceive that in the Introduction (§. 17. 18.) I have
established the necessity of distinguishing between indivi-
dual reproduction and generation, we shall here first treat

VOL. II. b

of the Systems subservient to the uniform continuance of
the change of materials in the individual Organism, viz*
the Digestive, Circulatory, Respiratory, and Secretory
Organs; — and subsequently, of the organs engaged in the
generation of new individuals ; concluding with the expo-
sition of whatever is most important in the organization
and different stages of developement of the latter.

BOOK I.

HISTORY OF THE ORGANS SUBSERVIENT TO
INDIVIDUAL REPRODUCTION.

Chap. I. Organs of Digestion.

I. In Animals without Spinal Marrow and Brain.

Section I. Zoophytes.

§. 433. The name alone of this Class sufficiently ex-
presses the fact that the organs of the Vegetative are more
developed than those of the Animal Sphere ; of which a
closer examination will still farther convince us, especially
if a comparison be made with what has been already
(§. 51, &c.) said of the organs here belonging to the animal

Sphere. But the organization for the functions even of
this Sphere is extremely simple, nutritive matter being
introduced in general by mere imbibition, the more com-
plicated organization for the intus-susception of extraneous
matter (organs for biting and masticating) being the pro-
duct of a more advanced formation. The Infusory Animal-
cules, consisting merely of little living animal cellules,
appear to absorb their materials of nutrition through the
parietes of the body, without any mouth. To these nearly
approximate the Medusa-like animals (Berenice, Rhizos-
toma, &c.), which sometimes absorb their nutriment with-
out a mouth, at others by numerous apertures. In the
true Medusse, on the contrary, there is a single aperture for
suction (Tab. I. fig. IX. A. a.) on the inferior surface of
the body, the cavity of which in the Medusa aurita leads
by four apertures into a like number of sacs or stomachs
excavated in the gelatinous substance of the body, which,
in a manner almost inconceivable, are capable of digesting
very hard bodies, e. g. small prickly Fishes.* The mouth
and stomach are equally simple in the Wheel-animals,
(Furcularia rotatoria ,) Polypes, (Tab. I. fig. IJ. IV. B.
VIII. C. a.) and the inhabitants of Corals and Sponges,
where, as the Intestine of several individuals frequently
communicates, ( e . g. in the animal of the Pennatula, Sea-
feather,) the whole in fact form but a single animal in the
{ manner of the Rhizostoma. In the Actiniae, the mouth,
surrounded by numerous Tentacula, opens into a blind sac
or stomach perfectly distinct from the mass of the body,
and which empties itself by rejecting its contents, so that
one aperture combines the two offices of mouth and anus.
(Tab. I. fig. X. A. d.)f

* Glide Beytrage zur Amt. und Phys. der Medusen, s. 1C.
f In the Medusae, the Stomach occupies the base of the pedicle of the
animal : from it a series of tubes radiate towards the superior hemispherical

B 2

§. 434. In tlie Ecliinodermata, which are already some-
what removed from this Class by the commencement of a
Nervous System, the intestinal canal frequently presents a
more perfect organization. In the Asterise, indeed, as in the
Acting, it still consists of a simple blind sac, which can be
protruded through the single opening, * in many instances
beset by five little teeth, so as to seize fish, shells, &c. the
indigestible parts of which are subsequently rejected.
Here, as in nearly all the inferior genera, the creature
lives on animal food. In the Holothuriae, the mouth,
according to Cuvier, is surrounded by a circle consisting
of six bones, which, however, are not to be considered as
organs of mastication : besides this, there is also another
circle of numerous blind sacs around the mouth, which

part of the body, communicating by lateral branches, and forming a compli-
cated network, by means of which nutriment is conveyed directly to every
part of the body : near the surface these vessels are particularly numerous
and form an absolute lace-work. In some species of Medusae there is but a
single large mouth : in others, on the contrary, instead of a mouth there is
a number of tufted tentacula, on each of which is the orifice of a little canal
■uniting with those in its vicinity, so as ultimately to form four-large trunks
leading to the stomach, and conveying thither the fluids collected by the
little orifices of the tentacula, of which there are sometimes upwards of eight
hundred. Of the animals thus characterised, M. Cuvier has formed the
Genus Rhizostoma, remarking that they appear to be nourished by a kind
of root, and that in them, as well as in the other Medusae, the stomach to a
certain extent supplies the place of the Heart.

In the Veretilla (Pennatula cynomorium), the body of each Polype pre-
sents a little brownish stomach from which proceed five tubes, performing
(as in the Medusae) at once the office of Intestines and Vessels. These In-
testines are at first yellowish and undulated, but having reached two-thirds
of the way through the animal, they become straight and smaller, and then
entering the common stalk to whicli the Polypes are attached, diverge in
order to meet the corresponding vessels, and to form with them a net-work
within the trunk. (Cuvier. Comp. Anat. iv. 145.) — Translator .

* Tiedemann in Meckel’s Archiv. b. i. h. 2.

appear to be salivary vessels. The intestine is tolerably
uniform in size ; forms three turns ; and is supported by a
kind of mesentery: according to Oken,* it usually contains
a black earthy excrement, and opens by means of an anus
into the respiratory cavity. In the Echini, the organs of
mastication are peculiarly developed, the aperture in the
shell corresponding to the mouth, having adapted to it a
very remarkable frame-work with five converging portions
(Aristotle’s Lantern), where each portion (a kind of jaw)
contains a long tooth moved by several muscles. (Tab. I.
fig. XIII.) In the large English Sea Hedge-hog, accord-
ing to Home, a narrow CEsophagus extends from the
mouth to the stomach, from which again proceeds an
intestine forming two turns : here the intestine terminates
in an anus opposite to the mouth, but in other instances, at
one side ; it is also confined within the globular shell by
peculiar vessels and membranes (a Mesentery). (Tab. I.
fig. XII. )f

* Zoologie, b. i. s. 331.

f In the Sipunculi the alimentary canal is small and uniform in its first
part, running from one extremity of the body to the other : it then returns,
making spiral convolutions around this first straight portion, and terminates
by a lateral anus very near the mouth, being altogether 6 or 8 times the
length of the body. In the Asterias, the membranous sac or stomach
situated in the centre of the body has two coeca, corresponding to each
' branch of the body, and subdividing into numerous minute ramifications
supported by membranous mesenteries. (Cuvier, Anat. Comp. iv. 144.)
— Translator.

Section II. Mollusca.

A. Acephala.

§. 435. Even here the mouth is still nothing more than
a sucking aperture, without jaws, tongue, or teeth : in the
Teredo, however, the deficiency of teeth is supplied by
some small detached pieces of shell (Tab. II. fig. XV. a. a.) ;
that of lips by small gill-like lamina? about the mouth in
the Bivalves (fig. VII. b. b.) ; and lastly, that of the tongue
by the tentacula about the mouth (§. 98.) in the Balani,
and in Oysters, &c. by transverse folds of the Pharynx.
The organization of the alimentary canal in other points is
very varied. In the Ascidia, the short tube of the mouth
terminates by a valvular opening in a large but delicate
membranous sac, (Tab. II. fig. II. a. d.) which in some
respects appears to be a kind of crop, and in others a respi-
ratory cavity. At the lower part of it is the commencement
of the oesophagus which leads to the stomach, and then
the intestine. The convolutions of the latter are placed
between the Gill-bag and the general muscular sac or
Cloak (§. 125.), and are either wholly unattached, or, as
was the case in a large species- examined by myself, buried
in the substance of the liver. The Rectum terminates
unattached opposite to the second aperture of the body,

(fig. III. II.)

§. 436. According to Home,* the intestinal canal in
the Teredo presents some important peculiarities : from
the mouth a narrow and not very long oesophagus extends

* Philosoph. Trans. 1806. p. 283.

-downwards into the worm-shaped body, and there expands
into a cylindrical stomach, of considerable length, which is
divided by a vertical partition into two cavities, communi-
cating with each other inferiorly, and, according to the
examination of Hatchett, in those species which bore
into wood contains a fine ligneous powder. The stomach
terminates in a long and narrow intestine, which first de-
scends, then ascends, runs over the double-bellied muscle
of the boring shells, then stretches along the respiratory
organs for the whole length of the body, and terminates at
its posterior part in the shortest of the two tubes found
there. (Tab. II. fig. XIV.)

§. 437. In the Bivalves, e. g. the Fresli-water Muscle,
(Unio pictorum,) the oesophagus is very short, but tole-
rably wide ; the stomach and convolutions of the intestine
are placed in the Foot, as it is called : (fig. IX. A. IX. B.)
the former, like that of the Medusa, (§. 433.) is scarcely
formed by any distinct membrane, but is excavated in the
substance of the liver, and presents several tolerably
large openings of biliary ducts. The intestine makes five
turns in the Foot amidst the ovary, and then as Rectum
runs posteriorly along the back of the animal beneath the
hinge and above the respiratory organs, passing through
the midst of the heart, and opening above the posterior
muscle closing the shells, beneath the small tube (§. 125.)
of the Cloak. (Fig. XI. s.) This description applies gene-
rally to most Bivalves : in the Oyster, however, the Rectum
does not pass through the heart : in the Pholas, &c. there
is externally, at the commencement of the intestinal canal,
a singular cartilaginous style, the point of which passes
through the side of the intestine, and a peculiar septum
belonging to it. It is probably analogous to the teeth of
the Echini, (§. 434.) or may, perhaps, be connected with
the sexual functions.

B. Gasteropoda.

§. 438. The mode of taking in nutritive matter is much
farther perfected in this than in the preceding Order, the
organs for the purpose not being merely an apparatus for
suction, but including also organs of mastication and of
perfect deglutition. These organs approach most closely
to the apparatus for suction of the inferior species in those
animals of this Order which are provided with proboscides,
— as Buccinum, Murex, Voluta. The proboscis of the
Buccinum undatum has been particularly examined by Cl>
vier :* like the tentacula of Snails, (§. 98. 110.) it has the
power of elongating itself by circular fibres, and is retracted
by longitudinal ones; its cavity is partly occupied by the aper-
ture of the oesophagus, (Tab. III. fig. IX. g.) and partly
by a tongue (fig. IX. h.) beset with hooks or teeth. In
the Snails which have not a proboscis, e. g. Helix, Limax,
Aplysia, the mouth is provided with broad lips ; and inter-
nally there is either a kind of horny upper jaw with several
tooth-like projections, as in the Helix pomatia and in
Slugs (Tab. III. fig, VI.); or else a similar jaw on each
side of the mouth, as in the Tritonia, on the authority of
Cuvier, The tongue noticed in the Buccinum here also
exists, presenting itself as a small elevation on the floor of
the mouth behind the jaws, and furnished with minute
prickles. The cavity of the mouth itself, into which open
salivary ducts, to be hereafter noticed, is usually very
fleshy, and forms a round pharynx, moved by several mus-
cles. (Tab. III. fig. VII. a. fig. X. XI. p.)

* Annalcs du Museum d'Hist. Nat. t. xi. p. 447.

§. 439. The course of the intestinal canal is extremely
various in the different genera of this Order. It is some-
times more simple, at others more complicated, but always
composed of distinct coats, and, together with the other
abdominal viscera, lies either in the general muscular sac,
(§. 131.) e. g. in the Slug and Aplysia, (Tab. III. fig.
VII.) or external to it within the shell, (§. 132.) covered
by the peritoneum like a hernial sac, e. g. in the Snails.
(Tab. III. fig. I. II. X. XI.) There is no true mesen-
tery. It is remarkable that here also it is usual to find the
Rectum in immediate juxta-position with the respiratory
organs. (See §. 434, 436, 437.) The Helix pomatia and
the Slug, as minutely described by Swammerdam, afford
instances of the more simple formation of the alimentary
canal. In the former the oesophagus descends through the
nervous circle of the neck, (Tab. III. fig. III. e.) and then
expands into a membranous stomach, divided into two
parts by a slight depression, (b. b.J and receiving the bile
into its posterior extremity fb.J ; the intestine then com-
mences, which makes a turn upon the liver, (fig. II. q. r.)
and running as Rectum close to the Gill-sac, (fig. III. b. c.)
terminates at the edge of the respiratory aperture. ( Fig. I.
f.) The same description applies in all essential points to
the Slugs and several nearly related species. In the Helix
stagnalis, however, the stomach differs so far from the form
1 here described, as it is much smaller, and is provided with
extraordinarily thick fleshy sides. I have not myself been
able to detect the crop described by Cuvier as being con-
nected with the oesophagus in these animals.*

* In the Onchidium the first stomach is a true Gizzard, very like that of
Birds, perforated at its commencement by two hepatic ducts, and lined by a
membrane of cartilaginous consistence : the second stomach is funnel shaped,
and furnished with deep longitudinal grooves, and corresponding ridges pro-
jecting atjtheir upper part in such a manner as must very much retard the

§. 440. The stomach of the Aplysia is peculiarly remark-
able, as well for the great increase in the complicity of its
structure, as for the manner in which it is armed inter-
nally; in which latter respect it appears to present a
further developement of the style found in Bivalves. (§.
437.) According to Cuvier, the narrow oesophagus run-
ning through the nervous circle of the neck (Tab. III.
fig. VII. d.) expands into a spacious and delicately mem-
branous Crop, (g. g.) convoluted in a half spiral shape
(something similar to which we have already noticed in the
Ascidia, §. 435) ; it then terminates in a narrow but very
muscular stomach, (h.) which is furnished on its internal
surface with rhomboidal semi-cartilaginous laminae, (fig.
VIII. b.) that appear to act like grinding teeth. The
third stomach (i.) is pretty similar to the preceding one,
and is also armed on its internal surface with hook-shaped
teeth (fig. VIII. c.) directed forwards : it contracts at its
posterior part in order to form the commencement of the
intestine ; at which point open into it the biliary canals,
(fig. VIII. f.) together with a peculiar ccecum, (e.) which
here, as well as in several other genera, appears to form the
prototype of the Pancreas, in the same manner as the blind

passage of food from the Gizzard .: the third stomach is short, cylindrical,
and disposed in folds, less deeply, however, than the second. In the Pleuro-
branchus the (Esophagus dilates into a membranous crop, at the lower part
of which the bile is poured in. It communicates by a narrow cardia with the
second stomach, which is a Gizzard with thin but muscular parietes. The
third stomach is membranous, and precisely resembles the plicated stomach
of Ruminants in being disposed in large but delicate folds, by means of which
the alimentary matter contained in it is moulded into long whitish cords.
The fourth stomach is membranous like the crop, but smaller. It is remark-
able that the Gizzard contains a narrow groove running through its whole
length, leading from the first to the fourth stomach, and probably subser-
vient to a species of Rumination. (Cuvier, Anal. Comp. iv. 118.) — Trans-
lator.

sac at the mouth of the Holothurise (§. 434.) does of the
salivary organs. The subsequent course of the intestine
has nothing very remarkable, making some turns on the
liver (fig. VII. k.) as in Slugs, and ending in the Rectum,
(1.) which opens into the anus (m.) close to the Gills, (v. w.)
According to Cuvier, the stomach in the Genus Bulla is
most powerfully armed ; for though the rest of the intes-
tinal canal pretty closely corresponds with that of the
Aplysia, the laminse of the second stomach of the latter
are here found extraordinarily enlarged, and converted into
true calcareous shells. These were long considered as
actual shells, and distinguished as a new species (Tricla).
It is singular to find in this instance the internal surface of
the intestine with the same power of secreting calcareous
matter as the external surface of the body (§. 121-24.) ; in
the same manner that liqie is deposited by Zoophytes, some-
times internally, at others externally. These laminae are
here three in number, nearly of this shape G$D ; and as
they are connected together by strong muscular fibres,
must possess considerable power as stomacal jaws or grind-
ing teeth.

C. Cephalopoda.

§. 441. In the Sepiae, and particularly in the S. octo -
podia, there is, as in most Snails, a thick fleshy pharynx,
(Tab. IV. fig. II. a.) which, in proportion to the bulk of
the animal, is here of considerable size. It lies in and in
front of the ring-shaped cartilage of the head ; and exter-
nally (not internally, as in the preceding Order) is armed
with two powerful horny jaws, of the shape of a parrot’s
bill, but not articulated to the cartilage of the head. This

beak, consisting of a superior and inferior portions,' (Tab.
IV. fig. X. a. b.) is possessed of considerable muscular
power, and is surrounded by a fleshy funnel or lip, as well
as by the circle of arms. (§. 135, 136.) The mouth con-
tains a small cartilaginous tongue, which, as in the pre-
ceding Order, has but little motion : the salivary ducts also
discharge themselves here. The oesophagus (Tab. IV.
fig. II. li. ; fig. XIII. c.) is rather narrow ; passes through
the cartilaginous ring of the head and the nervous circle
placed there, and in the natural position of the animal,
when the mouth,* as in the Echini and Asterise, is directed
downwards, runs upwards ; it then enters the cavity of the
abdomen formed by the peritoneum, and, in the Sepia
officinalis and loligo, expands into a spacious fleshy stomach,
leading by a rather narrow aperture to a second expansion
at the commencement of the intestine, having appended to
it a spirally convoluted coeeum, into which, precisely as in
the Aplysia, (§. 440.) the bile is discharged.*

§. 442. The stomach of the S. octopodia , however,
comes nearest to that of the Aplysia: the oesophagus in
the same manner expands into a large crop-like cavity ;
then again into a second, but imperfectly separated from
the true fleshy stomach, which terminates in the intestinal
canal, and at the same time has appended to it the usual
spiral-shaped coecum. (Fig. II. i. k. 1. m.) The intestine
itself in the Sepite is never attached by a true mesentery :
it is included, together with the stomach, in the delicate
sac formed by the peritoneurri, and is usually of no great

* The spiral Coecum forms one turn and a half, and is provided internally
with a spiral valve, which forms numerous and closely approximated convo-
lutions. In the Calmar it forms a long sac with thin parietes descending to
the bottom of the abdomen, without any trace of a curve or of transverse
folds except just at its origin, (Cumin, Mem. sur Ics Mvllusqucs. 1817, Ito.)
• — Translator.

length, in the Calmar it is broad, and, like the Stomach,
has longitudinal plicae on its internal surface. (Fig. XIV.
t.) It here no longer forms convolutions around the liver,
and ultimately terminates by a free extremity, nearly as in
the Ascidia, (§. 435.) within the large funnel-shaped aper-
ture (fig. I. a.) at the fore part of the neck, which serves
for the discharge not only of excrement, but, as we shall
hereafter find, of ova, semen, and the black fluid peculiar
to these animals. As to the latter, it is the product of the
membranous sac lined internally by a villous membrane ;
and, in the S. officinalis , is situated at the lower part of the
abdomen, but somewhat higher near the liver in the Calmar
(S. loligo) : in the former, as well in the S. octopodia , (fig.
II. q. p.) it empties itself by a distinct excretory duct of
some length ; in the latter it opens by a short canal into
the orifice of the rectum. (Fig. XIV. g. i.)

Section III. Articulata .

A. Vermes.

( §• 443. It has been already more than once noticed, that

the inferior species of this Order converge towards Zoo-
phytes in the same manner as is the case in the Acephalous
Mollusca in certain instances, and, as may probably be
still more clearly shewn, by the examination of species
already known, or by the discovery of new ones. Intes-
tinal Worms, for instance, might frequently be considered
as true Zoophytes; an idea confirmed by the structure of
their nutritive organs. The mode of taking in nutritive

matter is usually by apertures adapted for suction, or even
(as in the llhizostomata, §. 433.) by several such : in the
Hydatid, for instance, commonly found in the brain of
Sheep (Coenurus), there is a limpid bladder having attached
to it several bodies or necks, capable of being elongated or
retracted like the horns of Snails, each of which has a head
provided with four sucking apertures, surrounded by a circle
of hooks. As in these animals there is no longer any
intestine, properly so called, we may either, as already
observed, consider this structure as similar to that of the
Rhizostomata, or else view each of the bodies attached to
such a bladder as an individual animal, deriving, like the
animals of the Pennatula, (§. 433.) nutriment from a
common source. The approximation to the lowest genera
of Zoophytes (§. 433.) is still more evident, when, as in the
greater number of Intestinal Worms, the whole surface
presents itself as an organ of absorption of considerable
activity.*

§. 444. These animals, as we have already remarked,
have no intestine, being, in fact, nothing more than a sto-
mach with several openings for the admission of food. It
is interesting to mark the manner in which they gradually
advance towards a more perfect organization. First, the
bladder or stomach becomes smaller, and has only a single
tube for suction opening by four mouths ; as, for instance,
in the Cysticerus pisiformis , which I have occasionally
found enclosed in distinct membranous sacs, in vast numbers,
between the uterus and rectum of the Hare. In other
species the neck or body is longer, disposed in transverse
plicae, and jointed, with a bladder appended to the posterior
extremity : such is the case in the Cysticerus fasciolaris ,
which is very common in the Liver of the mouse, and like
the former is contained within a sac formed of the organ
* Rudolphi, Entozoorum Historia Nat. vol. i. p. 275.

iii which it is lodged.* Here, as in so many instances
among Zoophytes, the anus is wanting. Next come the
Toenise, in which there is a head with a jointed body, often
of extraordinary length, the head itself being provided with
from two to four sucking apertures, as well as with a pro-
boscis armed with hooks. From the sucking orifices run
fine canals, more like vessels than intestines, connected
by little transverse vessels, and frequently united in their
course through the body so as to form two instead of four.
It has not yet been satisfactorily determined whether there
be any anus ; but this much is certain, that in these animals
nutrition is effected not only by the intestine, but also by
absorption from the whole surface of the body.

§. 445. On the other hand, the organs of digestion are
more perfect in the Ascarides and several similar species.
The aperture of the mouth is simple; occasionally sur-
rounded by little tubercles, but still a true sucking orifice.
The intestinal canal, which is of pretty uniform size and
tolerably wide, runs through the whole length of the body,
and terminates in an anus at its posterior extremity; a
form of organization in which they evidently approach to
those species of W orms that do not live in other animals.
In the Lumbricus terrestris , for instance, there is a sucking
orifice as in the Ascarides ; posterior to it is a fleshy pha-
rynx ; then, in succession, — a narrow oesophagus ; a small
dilatation ; a fleshy roundish stomach, precisely like that of
certain Snails, e. g. Helix stagnalis, with a hard lining
membrane that easily separates ; and lastly, an intestine,
usually of an orange-red colour, with many transverse
plicae and a longitudinal ridge, — connected, as are also the
stomach and oesophagus, by means of numerous transverse
ligaments to the integuments, — and terminating in an anus
at the posterior extremity of the body. (Tab. V. fig. IL
* Oken Zoologie, b. i. s. 144.

III.) In the. Leech (Hirudo medicinal is), the sucking
orifice is triangular, with little sharp edges for the division
of the skin : attached to it is a strong fleshy pharynx,
which is the principal agent in sucking blood; next to this
follows a long and capacious stomach with thin membranous
sides, pretty closely connected to the integuments, and
divided by several septa into large cells communicating
with each other by oval apertures. Somewhat more than
midway down the body the narrow intestine arises from
this stomach by a small and funnel-shaped valvular opening:
it runs backwards between two imperforate sacs appended
to the stomach, and terminates in a minute anus placed at
the superior edge of the posterior sucking disc.* (Tab.
V. fig. VIII.) These organs are still more developed in
the great Marine Worms, e. g. the Nereis ; where the
mouth, or pharynx, which can be protruded like the sto-
macal sac of the Asterias, presents small horny teeth,
placed in opposition to each other, with a lateral motion,
and occasionally also small coeca appended to the stomach
(Tab. V. fig. XIII.) : the latter exist in great number in
the Amphitrite aculeata , being found in pairs in each joint
of the body, ramifying, however, still farther, and being
mutually connected.-]- t

* The slowness of the digestion of this animal is remarkable, blood being
found to remain unchanged in its stomach for months. Something similar
may be remarked in many of the superior cold-blooded animals. It must
also be considered as an approximation to the inferior stages of organization,
that the Leech should more frequently discharge its excrement from the
mouth than through the narrow intestinq. (Blumenbach Handbuch. der
Veryl. Anat. s. 177.)

f Meckel, Translation of Cuvier’s Comp. Anat. vol. iii. p. 167. and
Oken Zoologie, b. i. s. 376.

| In the Amphinoma capillata and tetradru there are in succession, in a
fleshy mass of the mouth or proboscis, a narrow oesophagus ; a stomach

B. Crustacea.

§. 446. The organization of the alimentary canal is much
more complicated in this than in the preceding Order, and
remarkable from the important fact of the developement of
organs of mastication (jaws) simultaneously with the lower
extremities, and in every respect in most intimate connec-
tion with them. In the description of the lower jaw of the
superior Classes of Animals I have already noticed the rela-
tion between the manner in which it is composed of two
lateral rami, and the structure of the jaws in the Articulata.
(§, 204.) If we carry our examination still farther, I think
it possible to prove, also, that the lateral motion of the jaws
in the Articulata corresponds to a still lower stage of orga-
nization, in fact, to the structure of the bivalve shells.
Thus, in some vermiform Acephala (Teredo, §. 436.) we
found moveable shells acting as jaws; with these the lateral
jaws or teeth of the Nereides (§. 445.) completely coin-
cide ; and these again, as their jaws are horny, form a
transition to the larvae of perfect Insects, Caterpillars, which
are in many points related to them, — and by that means
pass into the superior Orders.

§. 447. In Crustacea we find similar jaws with lateral

enormously dilated, with sacculi like those of a Colon, its folds being fixed
by a tendinous line situated on the ventral surface, and occupying the upper
two-thirds of the length of the body ; and then a short but capacious intes->
tine. In the Lumbricus marinus there b not any fleshy mass of the mouth :
the oesophagus extends through one-eighth of the length of the animal : the
stomach, which is more dilated, occupies one-third ; it is of a beautiful
yellow colour, its surface being arranged in lozenge-shaped sacculi, with the
divisions between them marked by vessels of a bright red colour. (Cuvier,
Comp. Anal. iv. 140.) — Translator.

VOL, II.

motion, though here we may divide them into two kinds:
Mandibulse, which, from their size, strength, hardness,
and resemblance in shape to grinding-teeth, appear to
correspond with the moveable shells of the Teredines and
teeth of the Nereides ; and Maxillae, which appear to be
formed merely by the continuation of the legs towards the
opening of the mouth. If we examine these parts in the
Cray-fish (Astacus JluviatilisJ, we shall find that the mouth,
which, as in the Echini and Asterias, is turned downwards,
presents a small longitudinal fissure, or rather an elongated
triangle, (Tab. VI. fig. I. a. seen from within,) having at
its anterior extremity two strong Mandibulse, as large as
peas, with teeth on their inner surfaces, and elongated
internally into a bony style on each side, moved by a
strong muscle attached to the dorsal plate. At each side
of, and diverging from, these Mandibulse is a series of six
pairs of Maxillse ; the innermost of which is merely a thin
lamina, whilst the outermost, on the contrary, is strong,
and in form precisely similar to a leg of the animal. (Tab.
VI. fig. VII.) Internally, these Maxillse, like the legs, (§.
144.) are elongated into horny laminse, which, in the two
largest of the Maxillse, have Gills attached to them, like
those of the legs. Above the mouth, also, there is a fleshy
projection, or lip; all the jaws, too, Mandibulse as well as
Maxillae, support small Feelers (Palpi), which, on the
three largest of the Maxillae, are very large and jointed :
they appear to serve the purpose of touching or examining
the food, and, in so far as they ascertain its sensible qua-
lities, may perhaps be viewed in the light of organs of
taste.* At least, of all the species of animals hitherto con-
sidered, there are none in which the existence, of that
sense is more probable than here, because of its intimate

• We may either consider such Feelers as tongues around the mouth, or
the tongues of the superior animals as similar organs within it.

connection with touch ; which justifies us in supposing that
the same developement of perfect extremities, which is
accompanied by the presence of organs for the latter, may
also be attended with similar results as regards the sense of
taste. (See §. 103, 104.) The description of the organi-
zation of the organs of mastication here given is applicable
in the most essential points to other Crustacea, though
there are occasional variations, particularly in the form and
number of the Maxillae : thus, according to Cuvier, a
Molucca Crab has five pairs with large feelers like legs,
and terminating in nippers.

§. 448. The (Esophagus of the Cray-fish is generally very
short, (Tab. VI. fig. V. a.) and formed by thin membranes ;
it quickly expands into a very large membranous stomach,
which, more particularly at its upper part and in the region
of the pylorus, is supported by a peculiar bony frame, and
by the same means rendered more capable of bruising the
contained food. This remarkable mechanism consists of five
flat bony masses, moved by muscles supposed to be volun-
tary ; to them are attached on the inner side three larger
and two smaller teeth, surrounding the pyloric opening of
the stomach (Tab. VI. fig. VI. a. a. a. b. b.); an organi-
zation, of which we find traces in the mode in which
the stomach is armed in several Mollusca. (§. 440. 437.)
The remark already made (§. 440.) as to the similarity of
the lining membrane of the stomach and the common inte-
guments, in so far as both are capable of secreting calca-
reous shells, is still more applicable here ; for in this case the
bony matter and teeth of the stomach are included, together
with the external shell, in the annual separation and rege-
neration of these parts. Home (Lect. on Comp . Anat.)
supposes that the round discs (§. 143.) which are found at
that time at each side of the stomach admit of being rubbed
against each other, like those in the stomach of the Bullae :

c 2

this, however, is not probable, inasmuch as they are only
temporary ; and, according to Oken,* are thrown off at the
same time as the old coating of the stomach. The intes-
tine is not fixed by a mesentery : it extends from the pyloric
end of the stomach in the form of a straight and narrow
canal along the body to the anus, which is placed below the
broad terminal plates or scales of the tail. The same form
of organization, according to Cuvier, prevails pretty gene-
rally through most of the corresponding species ; in some,
however, the stomach is merely membranous, and provided
with small teeth.

C. Insecta.

§. 449. In the varied Genera of this Order we find
almost all the forms of the alimentary canal already de-
scribed, as well as a multitude of new and peculiar forma-
tions. The organs of mastication, deglutition, and suction
here present such remarkable differences, that the arrange-
ments of modem Systems of Entomology have been chiefly
founded upon them. We need here notice only the most
important varieties by producing a few characteristic
examples ; it is interesting, however, to remark how the
organization of the apparatus for taking in nutritive matter
forms a complete series. Thus, Scorpions, Spiders, Mille-
pedes, &c. are related to the Crustacea, not only with
regard to their general form, but also by the mode in which
they take their food, the dev elopement of powerful organs
of mastication, &c. In this particular, Beetles, Orthop-
tera, and Neuroptera approach nearest to these Gnathaptera.
In the Hymenoptera we already find the animal deserting

* Zoologie, b. i. s. 393.

the coarser kinds of food, living chiefly on juices, and, in
this respect, approaching nearer to the true aerial nature
of the most perfect Insects. In them, also, we again find
the same mode of taking in nutritive matter as in the lowest
stages of the animal kingdom, viz. by means of organs of
suction, which here, however, are combined with organs
for mastication. These organs of suction are still more
developed in the Hemiptera and Diptera; and in the But-
terflies, which are almost wholly independent of solid nutri-
tive matter, present themselves in the greatest perfection,
and without any addition of teeth, &c. In their Larvae,
however, we find a repetition of the inferior organization;
and Caterpillars are, consequently, provided with powerful
jaws. The Aptera among Insects appear to bear the same
relation to the external surface of other animals as the
Intestinal Worms to the inner surface of their alimentary
canal : so, likewise, they resemble them in the mode of
taking their food, and have organs of suction armed with
hooks, &c.

We must next consider the different organs employed
in taking food, and then the varied forms of the alimen-
tary canal, as well as of its mode of termination. I may
first, however, remark, that in this Order of Animals
nutrition by vegetable substances is much more common
than in those below it.

A. Organs of Mastication and Suction in Insects.

§. 450. The type of formation of the jaws in Insects is
essentially the same as in the preceding Order : they are
usually moved by strong bundles of muscular fibres. Here,
also, they move in the same manner in a horizontal plane ;
and in the same manner a division may here also be esta-
blished into Maxillae and Mandibulae ; nay, in the Wood-
louse (Oniscus), there are several pairs of Maxillae: and
in the Spider, as in the Cray-fish, the lower lip is wanting,
— a part which is found in all other Insects with jaws.
Feelers or Antennae (probably organs of taste) are also
found in Insects, according to Cuvier, being absent in the
Julus only. Here, however, they are placed only on the
Maxillae and upper lip.* (Tab. VII. fig. XX. A. b. c.)
The Mandibulae are rarely wanting, as is the case in the
Ephemera ; and the Maxillae in the Ricinus.

§. 451. Among the Gnathaptera the Spiders are re-
markable for having strong Mandibulae armed with a move-
able curved tooth (Tab. VII. fig. I. II.), which is perforated
by a canal conveying venom. The Maxillae are very
small, but have attached to them long leg-like feelers ;
which, according to Treviranus,-|- are spoon-shaped at
their extremities in the male, and serve to excite the female
organs. In the Scorpion, the process of the under lip,
which is usually called the tongue in Insects, is provided

* According to Treviranus, ( Ueber den innern Ban der Arachniden, s. 2,)
however, the nipper-like feelers of the Scorpion are placed on the Mandibulae,
and not on the Maxillae.

+ Loc. ci(. p. 33. \

with a kind of lingual bone. (Tab. VII. fig. IX.) In the
Orthoptera, e. g. the Cockroach, (Blatta orietitalis,) the
Mandibulae are pretty strong ; the Maxillae are less so, and
are provided with feelers ; there are also an upper and a
lower lip. These organs are most particularly developed in
Beetles ; except that occasionally the Maxillae are wanting
in the larva state: the Mandibulae are frequently of extra-
ordinary strength, as in theCerambyx textor ; or elongated in
the form of antlers, as in the Stag-beetle (Lucanus cervusj.
The jaws of most Neuroptera, e. g. the Libellulae, approach
very closely to the lateral halves of the lower jaw in the supe-
rior animals ; for here each Mandibula has a long, curved,
and sharp tooth anteriorly, and posteriorly a crown-shaped
projection ; the Maxillae being also provided with long and
sharp teeth. The lower lip, also, is distinguished for its
size, covering the organs of mastication like a mask, and
being so moveable in the larva as to serve the purpose of
an organ of prehension. In all these genera the name of
Tongue has been given to a membranous elongation of the
lower lip : it deserves this name chiefly in some Orthoptera
being there placed below the opening of the pharynx, and
not serving merely for an organ of suction, as in this Order.
(See Tab. VII. fig. XX. A. d.)

§. 452. In the Hymenoptera, ( e. g. Bees,) to which
some Neuroptera (Panorpa, Ephemera) appear to form
a transition, the cylindrically rolled tongue is elongated
into a sucking tube,* over which a perfect internal and
external sheath are formed by the elongation of the
Maxillae. The Mandibulae still remain, but are more
spoon-shaped, and unarmed, being no longer used in mas-
tication, but rather as weapons, &c. ; the proper cavity of
the mouth being wanting generally in those Insects which

* Trkviranus, on the Suction of Insects, in the Essays of the Wcttera*
vian Society for Zooloyy.

suck, as opposed to those which masticate. Even where
the tongue is not elongated, the opening of the pharynx is
found below it; and, consecpiently, it cannot act as a
tongue, properly so called. The Mandibulse of the Larvse
of this Order act, however, as true organs of mastication.

The structure is nearly similar in the Diptera and
Aptera, in which a proboscis, apparently representing the
elongated lips, contains a sucking tube, and sometimes,
as in Gnats, several penetrating points in addition. In
the Larvse of the former (Diptera), there is an apparatus
for chewing, composed of two jaws ; nay, in the larvse of
those which live within the intestines of other animals,
( e. g. in the larvse of CEstrus equi, so common in the Horse’s
stomach,) there are, as in many Intestinal Worms, (§. 152.)
little hooks on the head, by means of which the animal is
enabled to attach itself. Lastly, in the Butterflies, the only
one of these organs which remains is a flat and spirally-
rolled tongue or sucking tube : it is only in the larva state
that we again find either powerful Mandibulse (Tab. VII.
fig. XI. a.), or else small and almost proboscis-like rudiments
of Maxillse and a lower lip.

B. Intestinal Canal in Insects.

§. 453. I here first notice the intestinal canal of the
Arachnida, which, in accordance with the mode of nutri-
tion, differs remarkably from that of other Insects.
According to Treviran.us,* the GEsophagus in the Spider
is straight, small, and with thin coats: it communicates

* Ueber den innern Bau der Arachniden.

with four blind stomach-like pouches* in the thorax, and
then runs towards the posterior part of the body, where it
disappears in a delicate web inseparable from the fatty
substance around. (Tab. VII. fig. I.) It is probably at
this point that the nutritive materials pass immediately into
this fatty body, which we fiod in most Insects (fig. XXIII.)
as a kind of mesentery or omentum, in which those mate-
rials are deposited in the form of little globules of fat or
chyle. This deposition of fat from the intestinal canal is
still more distinct in the Scorpion ; for here, according to
Treviranus, five vessels, (fig. IX.) comparable to the
lacteals in Man, arise from each side of the stomach, and
are diffused through the fatty bodies.f

* Similar blind appendages to the intestinal canal are tolerably common
in Insects, and appear to be of the same nature as the Cceca already noticed
in several Mollusca, i. e. prototypes of the Pancreas.

f In Scorpions, the short (Esophagus is succeeded by a cylindrical elon-
gated stomach, with four pairs of lateral branches opening into it, and receiv-
ing the hepatic vessels, which are composed of an infinite number of rounded
glands, usually filled with a thick brown fluid. The Duodenum is shorter
and more capacious than the Stomach, and separated by valves, as well from
it as from the Rectum : at its lower part open into it two lateral branches,
which are probably chyliferous vessels. In the Onisci, the (Esophagus is
wide, but short : the Stomach is long, occupying more than three-fourths of
the body, and is distinguished from the (Esophagus only by its greater dia-
nr^ter. The Rectum is smaller than the Stomach, and is separated from it
by a valve very distinctly marked externally. According to Cuvier, the
hepatic vessels are four principal trunks inserted close to the termination of
the (Esophagus. The characteristic of the alimentary canal of Spiders is its
ramified structure : the (Esophagus has two lateral branches ; the Stomach
four ; the Duodenum and Rectum are also ramified. The Stomach is the
only dilated part of the canal ; its shape is quadrilateral, the branches arising
from its sides. The hepatic organs, consisting of an infinite number of little
glands containing a peculiar, thick, brown fluid, are attached to the branches
of the alimentary canal, and occupy the greater part of the abdomen.
(Marcel De Serres, Mem. du Museum , v. 63.) — Translator.

§. 454. We may take the intestinal canal of the
Dytiscus as a specimen of its structure in Beetles, the
more so, as, according to Cuvier, the Genera Carabus
and Cicindela are similar in this point. As is the case in
many Insects and several Genera of the Orders already
described, the Oesophagus expands into a crop-like cavity,
and then passes into a small roundish muscular stomach,
(nearly as in certain Mollusca and Vermes, §. 445.) which
is beset internally with little horny teeth, and is chiefly
devoted to the object of dividing the food. Ramdohr*
distinguishes this by the name of the plicated stomach.
Next to it follows a long piece of intestine, the first half
of which is surrounded externally with shaggy appendages
(probably small secreting Coeca, §. 453.), whilst the lower
is smooth and formed of thin membrane. Both together
form the true stomach, which, according to Ramdohr,
comprehends the whole extent of the space to the insertion
of the biliary vessels to be hereafter noticed, and conse-
quently, in many instances, forms by far the largest portion
of the alimentary canal. Next follows a simple small in-
testine of nearly equal length, which, in the last place,
terminates in a distinct large intestine with long blind
appendages, the nature of which will be considered here-
after. In the Larva these subdivisions of the intestine are
less strongly marked ; the whole canal appears shorter in
proportion to the body ; more uniform in size, like that of

Vermes, and provided with a longer ccecum.f
0

* Ueber die Verdauungswerhzeuge der Imekten. Halle. 1811.

f As regards the Intestinal Canai, the Coleoptera may be arranged in
two divisions, according to the absence or presence of a Gizzard. Of the
former kind are Curculio, Cerambyx, Cebrio, &c. where the stomach is
immediately continuous with the (Esophagus, and is succeeded by a Gizzard
with six firm coriaceous laminse projecting from its internal surface. In the
Carabi, Cicindelae, &c. the Stomach opens laterally from the (Esophagus,

§. 455. In the Orthoptera, e. g. the Grylli, we gene-
rally find in the Larva, as well as the perfect Insect, a short
and straight intestinal canal, a fact which perfectly coin-
cides with the voracity and rapacity of these animals. The
(Esophagus first expands into a crop-like cavity, which is
followed by a small, roundish, muscular stomach, plentifully
furnished with horny teeth on its internal surface ; next
comes a circle of little coeca,* or, as in some Species, a
heart-shaped expansion with large folds at its inner and
upper part; and lastly, a narrow gut-like stomach. (Tab.
VII. fig. XX. XXII.) On account of this complicated
structure, which is pretty closely imitated in the ruminat-
ing Mammalia, and also from the results of numerous
observations, the power of ruminating has been ascribed to
these Insects. I have myself frequently seen their jaws
in active motion, though not employed in eating. M. De
Serres, f however, conceives that the organization of their
intestinal canal is opposed to the idea of their rumination.
In the Neuroptera, which are generally rapacious, and in
which we found the organs of mastication so powerful, we
find the intestinal canal short, as compared with the body,
*• e. nearly of the same length with it. The (Esophagus
terminates in a muscular stomach provided with little horny

and is followed by a Gizzard of considerable size, but without having inserted
jfito it any coeca or hepatic vessels. In the Coleoptera without a Gizzard,
e. g. Scarabeus, Geotrupes, Chrysomeles, &c. the narrow (Esophagus
opens into a small stomach, which, like the Duodenum, is covered by hepatic
vessels. The Genera Tenebrio, Blaps, &c. differ from the latter only in
having an additional portion of small Intestine interposed between the
Duodenum and Rectum. (M. De Serres Memoires du Museum, v. 14-3. )
— Translator.

* In an excellent Essay on the Organs of Digestion in Insects, ( Annales
du Museum d’ His. Nat. vol. xx.) Marcel de Serres calls these Coeca the
superior biliary vessels.

f Zoc. r.il. p. 365.

teeth; then follows a long and membranous stomach, which
is immediately succeeded by an expansion forming the
commencement of a large intestine of no great length.
In the Larva the whole intestinal canal is proportionally
wider ; but here more particularly the proper and peculiar
character of the large intestine is displayed, inasmuch as
we find in it the seat of the respiratory organ, (little gill-
laminae, to be hereafter described ;) and consequently dis-
cover in this portion of intestine a repetition of the pre-
ceding formations, where the intestine either opened
immediately into the respiratory cavity (§. 434, 436, 439,
442), or the anus was closely connected with the Gills or
respiratory cavity. In the Ephemera, the perfect develope-
ment of the body, according to Cuvier, is accompanied by
an extraordinary contraction of the intestinal canal, its
functions ceasing almost completely, the animal no longer
taking in any nutriment. Nay, in the Larva of the Myr-
meleon furmicarius, (Ant-Lion,) the stomach is a blind sac
closed inferiorly, as is the case in many Zoophytes.-}-

f The forms of the Stomach and Intestinal Canal present considerable
varieties in the different species of Orthoptera. In Acheta and Gryllo-talpa
the Stomach is shaped like a hag-pipe, and situated at the side of the (Eso-
phagus, communicating with the Gizzard by a narrow cervix. The Gizzard
is very large, and corresponds to the insertion of the cceca, or superior hepatic
vessels, as they are called by M. De Serres. In Loeusta, the Stomach is
immediately continuous above and below with the CEsophagus and the Gia-
zard. The latter is still very considerable, and, as in the former case, is
placed immediately above the insertion of the cceca, which, at their un-
attached extremities, terminate in secretmg vessels. In the Acheta and
Gryllo-talpa the inferior hepatic vessels open into the Duodenum by a com-
mon trunk.

In the Genera Gryllus and Truxalis, where the superior hepatic vessels
are more developed, the Gizzard is proportionally diminished in size. The
inferior hepatic vessels here form long capillary canals which adhere to the
parietes of the Duodenum. In the Genera Mantis and Blatta, the Stomach
is immediately continuous with the CEsophagus, and the Gizzard, which is

§. 456. As to the Ilymenoptera, the organs of digestion
in Bees are important, not merely as such, but also as
organs for the preparation of honey and wax. The slender
(Esophagus opens into a membranous crop, in which appa-
rently the nectar that has been sucked is converted into
honey, and then thrown out into the cells of the comb.*1
This honey-stomach is succeeded by a contracted portion,
and then by the true stomach, which, extending to the
insertion of the gall-vessels, exceeds the first in length and
breadth. It is probably in this second stomach that the
wax-meal (bee-bread) is converted into the Wax which
escapes through the rings of the abdomen ; it is collected
as pollen from flowers, is accumulated in a fossa on the
thigh, and after having been mixed with some fluid, is
deposited in the cells partly for a supply of food, and partly
for the formation of wax.f The small intestine which
succeeds is but short, and. terminates in a large intestine
of considerable width and containing five little elevations,
which are probably excretory organs : these elevations may
be ranged with the Gills contained in the large intestine
of the Larva of the Libellulae, (§. 455.) and shew the con-
nection between the functions of secretion and respiration.
In the Larvae, the intestinal canal is much more simple,
consisting almost solely of a broad sac-like stomach, from
which, as in the Ant-Lion, there is no communication to
y the intestine.

much developed, is attached to it laterally. The remaining parts of the
alimentary canal, which generally consist of a Duodenum and a Rectum,
are much more uniform in size and structure. (M. De Serres Memoires
du Museum, v. 106.) — Translator.

* Swammerdam Bibl. Nat. p. 162.
f Sprengel’s Brie/e ucber Botanik. Th. i. s. 336.

§. 4-57. In the Hemiptera, e. g. Bug's, there are usually
two stomachs, the posterior of which, according to 11am-
dohr, has annular hands upon it, and is composed of four
half-canals. Besides a small, there is also a large intestine
of considerable size, which generally has a coecal appen-
dage to it. The intestinal canal of the Tettigonia plebeia,
as described by Meckel,* is very singular, the second
stomach leading to a long canal, which ultimately termi-
nates in the first. In the Diptera, e. g. Gnats, the intes-
tinal canal is of tolerable length, and the most remarkable
part of it a sac-like appendage to the oesophagus of consi-
derable size, which, probably, is accessory to suction
(§. 452), and usually contains little air-vesicles. In the
Larvse, which are provided with jaws, this appendage does
not exist. In the Larva of the Cheese-fly, Swammerdam
found a roundish muscular stomach, followed by a circle of
four coeca, a long gut-like stomach, and an intestine of
uniform size.

§. 458. In the Papiliones, which, in every stage of their
developement, live solely on vegetable matter, the intestine
is narrow and does not materially exceed the body in length.
Here also we find a sac-shaped appendage at the side of
the oesophagus, frequently containing air,f and similar to
that found in the Diptera, as an agent in suction : next
follows a roundish stomach interrupted by many transverse
folds ; then a cylindrical stomach ; and then the small in-
testine, which ultimately terminates in a large one of con-
siderable width, and generally provided with a ccecum.
(Tab. VII. fig. XVI.) It is remarkable to observe how

* Beytriigc zur Verglekhende Anatomie. Th. i.

f May we not view this sac containing air and appended to the oeso-
phagus, as the prototype of the lungs, which also in the superior animate
are concerned in the action of suction?

the Caterpillar is distinguished from the perfect Insect by
its intestinal canal, as much as by its general form and the
structure of the organs of mastication. Thus, in some
Caterpillars, I find the whole of the intestinal canal per-
fectly straight, and almost exclusively formed by the mon-
strously long and broad stomach, which reminds us of that
of several Vermes, e. g. the Leech. The great size and
the straight course of the intestinal canal in these animals
perfectly coincides with their extraordinary voracity, some
of them devouring in 24 hours more than three times their
own weight. The parietes of this stomach consist of six
half-cylinders, and have deep transverse furrows upon them.
Below it are placed two globular swellings, and then a
large but short intestine. (Tab. VII. fig. XI. XII.) This
intestinal canal, which, from the nature of the food, is
generally green in the Caterpillar, contracts very conside-
rably in the Pupa. In a Pupa of twelve days, I found it
scarcely half as long, and only one-sixth as wide, as in the
Caterpillar (fig. XV.) ; and ultimately in the perfect
Insect only the upper globular and transversely plicated
swelling of the stomach remains.

In the parasitic Insects of the skin, the intestinal canal,
as far as we may conclude from Swammerdam’s examina-
tion of the Louse, is tolerably simple: the stomach is wide
and long; has two cceca at its upper part; and terminates
ipferiorly in a curved small intestine, followed by a wide
large intestine.

As to the mode of attachment of the intestinal canal in
Insects, it is usually effected by means of numerous air
tubes which ramify upon it. There is not any mesentery,
properly so called ; and the place of Omentum is supplied
by the fatty substance already mentioned, (§. 453.) and
forming a deposit of chyle, the nature of which is eluci-
dated by the fact that it is always found large in the imper-

foet Insect, c. g. Caterpillars ; and is much reduced in the
perfect one, e. g. Butterflies.*

C. Of the Termination of the Intestinal Canal in Insects.

§. 459. The intestinal canal of Insects invariably opens
at the posterior extremity of the body, in front of, or below
the genitals : hence, the opening of the anus will require
a more particular description in those cases only, in which
it is furnished with peculiar weapons, such as a sting and
poison-glands, or with an equally remarkable organ for
spinning. In the Scorpion, we find a weapon of the kind
alluded to, the anus being placed between the penultimate
and terminal segments of the body; the last ending in a
horny point, (Tab. VII. fig. IX. k.) the aperturef of which
gives exit to the poison. The little poison-gland lies in
the globular swelling of the last segment of the body, and
is surrounded by powerful muscular fibres. (Tab. VII.
fig. IX. k.) A similar apparatus exists in several species
of Hymenoptera, e. g. Bees and Wasps. In the former,

* The alimentary canal in Insects is fixed only by means of the trachere
distributed to it, without the assistance of mesentery, vessels, or even cellu-
lar tissue : hence, when an Insect is opened in water, the folds of the canal
are raised and stretched by means of the air contained in their tracheae. The
name of peritoneum may be assigned to the delicate membrane which lines
the inner surface of the abdomen, and which is covered externally by the
segments of the skin and the muscles belonging to them. (Cuvier Comp.
Anat. iv. 158.) — Translator.

f Although Treviranus (foe. cit. p. 14) could not discover such an
opening, there can be no doubt of its existence, for Redi long ago observed
the venom escaping from the point of the tail.

the Queen and the Workers only are possessed of stings
and poison-bladders, with the organization of which we are
acquainted chiefly by means of the excellent descriptions
of Swammerdam. The sting is here also placed on the
last segment of the body above the opening of the rectum:
at its basis is lodged the little poison-bag, the coats of which
are very firm and surrounded by strong muscular fibres ;
the latter, however, do not compress the bladders equally
on every side, but merely flatten them. At the upper
part of the little bag are two long narrow vessels, which
appear to secrete the poison. * The sting itself consists of
two rami at its upper part bent to each side, the opposed
surfaces presenting deep grooves serving for the lodgment
of the excretory ducts of the venom-bags. Each half of
the sting is beset externally with a row of barbs, by which
it is retained in the wound it makes, with a fatal result to
the animal to which it belongs. Lastly, the two halves
are again inclosed within a distinct sheath, the whole
weapon being moved by a peculiar apparatus of voluntary
muscles.

§. 460. The spinning organs are almost peculiar to
Spiders. They consist of four tubercles placed immediately
below the anus, having their rounded extremities perforated
in a cribriform manner, so as to permit the passage of the
viscous fluid which forms the thread. (Tab. VII. fig. IV.
c/r.) Within are numerous ramified sacs, of various
length, and variously formed in the different species, usually
occupying a large portion of the back part of the body,
(fig. III.) and serving to secrete the glutinous matter.
Close to the tubercles are two little extremities, which are

* As we shall hereafter find, a true vascular system is apparently wanting
in Insects, and consequently, all the secretory organs must collect their
peculiar fluids from the general cavity of the body by means of similar
vessels.

VOL. II.

singularly similar to the feelers of the jaws, and probably
serve to interweave the four threads issuing from the
tubercles. Something similar exists in the larvaa of some
of the more perfect Insects : according to Ramdohr, in
that of the Ant-lion, where an expansion of the large
intestine forms the receptacle for the silky substance.

As to the nature of these poison-organs and spinning
apparatus ; on the one hand, with many other secretions in
the vicinity of the anus, (§. 455.) these may recal to our
recollection the relation already noticed between the termi-
nation of the intestine and the respiratory organs, i. e.
the frequent repetition of respiration in secretion, (compare
for instance the descriptions of the spinning organ of the
larva of the Ant-lion, and of the excretory organ in the
large intestine of Bees, §. 456.) : on the other hand, we
observe a close analogy between them and the salivary and
poisonous organs of the mouth, — the Mandibulae in Spiders
being armed precisely like the anus in the Scorpion, — the
sting of Bees having considerable similarity to the pene-
trating proboscis of Gnats, — and lastly, organs for spinning,
similar to those which in the Spider are placed near the
anus, being situated about the mouth in the larvae of the
more perfect Insects, which, as being in the vicinity of the
salivary organs, and in many respects resembling them,
will best be considered hereafter.

C . •*

Chap. II. Of the Organs of Digestion in Animals with
Brain and Spinal Marrow.

§. 461. As the great diversity in the structure of the
individual parts of the alimentary canal in the four superior
Classes of animals renders a more precise consideration of
these parts necessary, we shall (in each Class) examine
their organization under three different heads; viz. 1st.
the Teeth, or organs of mastication, together with those
of taste, suction, and deglutition ; 2d, the (Esophagus
and Stomach; and lastly, the intestinal canal with its
termination.

Section I. Organs of Digestion in Fishes.

A. Of the Organs of Mastication , Taste , Suction , and

Deglutition.

fy 462. The form of the mouth in Fishes, as well as
the mode of its motions, are partly explained by what has
been already said (§. 176, 178.) as to the various forms of
the bones of the jaws, and I need here only refer to a
point that has been before briefly noticed (§. 204. Remark);
viz. that the nature of the lateral rami of the jaws in
Fishes, as well as in the following Classes, is explained by
the form of the lateral jaws of the Articulata. But, if we
still farther compare the bones forming the cavity of the

d 2

mouth in the four superior Classes of animals with the
organs of mastication in the Crustacea and Insects, we shall
be led to assimilate the lateral segments of the Upper Jaw
in the former to the Maxillee of the latter : — the Inter-
maxillary Bone (which, in Fishes, has usually (§. 176.) a
moveable connection with the Upper Jaw) to the Upper
Lip; the lateral segments of the Lower Jaw to the Man-
dibulse; and the Lingual Bone to the Lower Lip of these
inferior species of animals. As concerns the situation of
the mouth, I may notice as a remarkable analogy with the
inferior formations, that in many of the superior species of
Fishes, e. g. Rays, the Sturgeon, &c. the mouth is placed
on the inferior surface of the body, in the same manner as
in the higher Species of Zoophytes, which present so
many points of comparison with Fishes, (§. 38.) ; e. g. in
the Echinodermata. (§. 434.) It is still more interesting
to observe how perfectly the form of the sucking aperture
in several Worms appears to recur in the fleshy, funnel-
shaped, sucking orifice attached to the circular jaw (§.178.) .
of the Lamprey (Tab. VIII. fig. IV. A.): it is by this
means that the fish attaches itself so closely as to admit of
being raised out of the water with a stone of 10 or 12
pounds adhering to its mouth. In the Shark, (Tab. VIII.
fig. VI.) also, the lateral segments of the superior and
inferior maxillcE, which are almost completely separate from
the Cranium, may be considered as a repetition of the
similar structure of the Sepise. (§. 441.)

§. 463. As to the organs of mastication in Fishes, it is
remarkable, that as in the inferior Classes we frequently
met with hooked points or actual teeth, partly in the mouth,
as in snails (§. 438.), partly in the (Esophagus and Stomach,
as in the Aplysia, Nereis, and Cray-fish, without any con-
nection with a true skeleton, — so also, in Fishes, the teeth
are found, sometimes having a slight connection with the

skeleton, at others placed not merely in the jaws, but also
on the palate, the tongue, or even (as in the Nereis) in the
pharynx. The imperfect connection of the teeth with the
skeleton altogether corresponds with the general want of
compactness in the latter, and is particularly evident when
we trace the mode of formation of the individual teeth. The
most usual kind of teeth in Fishes, i. e. the pointed, hook-
shaped, found in the Pike, in which they are surrounded
by a membranous retractile sheath, and the flat triangular
teeth of the Shark, wholly differ from those of man, in
being formed in the gums instead of in cavities of the jaws.
Without any great incorrectness we might consider them
as the papilke of the gums, palate, tongue, &c. indurated
and covered with a tooth-like substance, and which are only
gradually connected to the bones of the jaw or palate over
which they happen to be placed. Hence, we find them
in the Pike originally adhering to the gum alone, and not
united to the subjacent bone by bony substance until a
later period. In the Shark there are several rows of teeth
one behind the other, a new tooth raising itself forwards
whenever one is lost,* but still without having any con-
nection with the bone. According to Cuvier, in those
Fishes which have flat or cutting teeth (e. g. the Spari),
they are renewed rather in the same manner as in man.

§. 464. In the different Genera of this Class there are
Endless varieties, as well in the situation as the shape of
the teeth. In the Pike they are exclusively hook-shaped,
and situated in all parts of the mouth, except the Superior
Maxillary Bone, (§. 176.): viz. on the lower jaw, where
they are very strong ; on the palate bones ; on the Vomer

• Even this erection may remind us of the turgescence of the papillae of
the tongue.

(§. 176.); on the tongue; in the pharynx (§. 170.); and
on the thoracic Ribs, or arches supporting the Gills.
(§• 165.) In the Carp there are none in the mouth; the
jaws of the pharynx have strong flat teeth, which are
pointed in the smaller species of the Genus Cyprinus
(Tab. VIII. fig. V. c.); a distinct tooth-like lamina of
bone also rests upon a process of the Occipital bone.
(§. 172.) In the Genus Sparus we find anteriorly wedge-
shaped cutting teeth, like the incisors of man, and poste-
riorly hemispherical teeth closely crowded together. (Fig.
VIII.) The Lampreys have their brownish hook-like
teeth internally upon the fleshy funnel of the mouth. (Fig.
V. 2.) The Sturgeon is altogether "without teeth. Rays
and Sharks approximate to the superior animals in so far as
they have teeth only in the upper and lower jaws (fig. VI.) :
the Ray, however, is singular from the numerous teeth,
or rather teeth-like laminae, placed close together. Accord-
ing to Cuvier, the Anarrhichas lupus is remarkable for
hemispherical bony excrescences, which, though they drop
out themselves like teeth, have originally little teeth upon
them. In the Genera Tetrodon and Diodon, mastication
is performed by tooth-like elevations of the jaws, consisting
of numerous horizontal parallel laminae, which are gradually
exposed on the masticating surface which crosses the direc-
tion of the laminae obliquely.

§. 465. The muscular apparatus employed in biting and
chewing,* as well as in opening and shutting the mouth,
is subject to many varieties according to the form of the
jaws, &c. We usually find, however, that the depression

* In this, as well as most of the inferior Classes of Animals which live
upon -animal food, there arc but few instances of true mastication, properly
so called.

of the lower jaw is effected by a muscle on each side,
( Genio-hyoideus, Tab. VIII. fig. XII. u.) proceeding from
the lingual bone to the edge of the lower jaw, and its
elevation by another (Temporalis, fig. XII. t.) running
below the eye. When the Superior Maxilla and Inter-
Maxilla are moveable, as in the Carp, (§. 176.) they have
peculiar muscles belonging to them. (Fig. VII. r. s.)
The principal agent, however, in elevating them is an
elastic ligament, (fig. XII. o.) performing pretty nearly
the same office as the cervical ligament of the long-necked
Mammalia. (§. 4-25.)

§. 466. The Tongue has here no claim to be considered
as an organ of taste, but rather (as in Snails and Sepise,
§. 438. 441.) as an apparatus for ingestion, inasmuch as it
is not only almost completely deprived of motion, but like-
wise generally composed of cartilage, covered with an
insensible membrane, or even armed with teeth. (§. 464.)
We have already described (§. 179.) the osseous girdle
which supports the lingual cartilage (Tab. VIII. fig. I. II.
V. VII. n.); it is only necessary in this place to remark,
that, on the one hand, either the tongue or its cartilage are
wanting in certain Genera, — the former in Rays, the latter,
according to Cuvier, in the Genus Trigla and the Esox
belone ; on the other, that the size of the tongue is in some
cases very considerable, e. g. in the Pike, the Perch, and,
according to Cuvier, particularly in the Conger. The
organ which, in some respects, supplies the place of the
tongue in the Lamprey, merits particular remark : it con-
sists of a quadrangular, dentated, and almost bony projection,
quite at the base of the funnel-shaped mouth; its office
appears to me to be that of closing the posterior part of the
cavity of the mouth in the action of suction (§. 462.), by
which means that part is enabled to act precisely like the
sucking organ of a Sepia. (§. 136.)

§• 407. The fauces in Fishes are in no other way sepa-
rated from the cavity of the mouth than by the openings
for the Gills at each side, to be hereafter noticed. They
are continued backwards into the pharynx, which is marked
by a contraction depending on the presence of a circle of
muscular fibres, and which in many species is strengthened
by the maxillae of the Pharynx, (§. 170.) and the muscles
belonging to them. The CEsophagus, again, is immediately
continuous with the pharynx, and it is only in the Lamprey
that a peculiar description is rendered necessary by the
unusual formation of the part. In that animal two canals
or passages open into the lower part of the pharynx, of
which the anterior or lowest leads to the respiratory organ
(a membranous canal with lateral pouches and apertures),
and the posterior or superior to the oesophagus; an arrange-
ment which evidently corresponds to the relative position
of the pharynx and larynx in the superior animals, and
even in Man himself. From the commencement of the
oesophagus the spouting tube ascends, which has been
already noticed, (§. 348.) and the communication of which
with the pharynx has been recently, though incorrectly,
denied by Home ( Phibsoph . Trans. 1815.) Lastly, we
must notice here the temporal holes, as they are called, of
Rays and Sharks, which open externally behind the Eyes,
and convey water to the fauces and Gills. They are to
be considered as farther (double) developements of the
spouting hole of the Lamprey and Gastrobranchus caucus.

B. Of the (Esophagus and Stomach of Fishes.

§. 468. In proportion to the body the intestinal canal
of Fishes is extraordinarily short, frequently extending in
a straight line through the abdomen, and being, conse-
quently, as the anus is placed at the anterior extremity of
the caudal vertebrae, much inferior in extent to the body of
the animal; as was also the casein Worms and Insects.
This shortness of the intestinal canal would render diges-
tion almost impossible, were it not compensated by the
length of time that the food, which is usually animal, is
detained in it.# It is also probable that Fishes in general
are supported by other means than the mere taking of food
into the stomach : this is sufficiently shewn by their long-
continued residence, and even growth, in water alone,
without any supply of food; a circumstance that again
reminds us of Zoophytes, in which we found the nutrition
of so many species effected by general absorption without
any evident intestinal canal.

§. 469. In those Fishes where the alimentary canal
stretches directly through the abdomen, the only means of
estimating the extent of the stomach is afforded by the
point at which the gall-ducts penetrate ; consequently, in
the Lampreys for instance, we must consider as the (Eso-
phagus that narrow portion of the canal which runs above
or behind the respiratory organ ; and as the stomach the
somewhat more expanded part which lies behind the liver.
It is only in a few species, however, that the structure of

* Home ( Led. on Comp. Amt. p. 310) mentions that a Perch took lood
but once in from ten to fourteen days.

the intestinal canal is thus simple : in far the greater num-
ber the (Esophagus is of considerable width, has longitu-
dinal folds on its internal surface, (Tab. IX. fig. XIX. q.
XX. XXL XXII. a.) after a short course insensibly
expands into the stomach,* the structure of which is nearly
similar, and communicates by a canal with the swim-
bladder. According to Home, (Phil. Trans. 1815,) the
(Esophagus is most extraordinary in the Myxine (Gastro-
branchus ccecns ) , which, besides the six lateral branchial
foramina, has a single hole opening externally, and pro-
bably in some respect connected with the respiratory
function.f

§. 410. The form of the stomach is very various in the
different kinds of Fishes, though its cavity is ordinarily

* In rapacious Fishes, the Pike for instance, we not unfrequently find a
portion of the prey still lodged in the (Esophagus, whilst the rest extends
into the stomach ; a proof that the same functions are common to both
organs.

f The distinction between the large and small intestine in Fishes cannot
always be established with certainty. Sometimes it is the part next to the
anns that is smallest, at the same time that its parietes are thinner than those
of the intestine above it : such is the case in Rays, Sharks, the Sturgeon, and
the Bichir, where the first part of the intestine has a spiral valve ; and in the
Syngnathi, Ostracions, and Balistes, where the first is separated from the
second part of the intestine by a circular valve. In other cases there is no
difference in the diameter of the two divisions of the intestine; which, how-
ever, are distinguished by variations in the structure of the mucous mem-
brane, by the different direction of the fibres of the muscular membrane, or
even by the presence of a circular valve. In many other species the second
part of the canal is more dilated than the first, e. (j. in Siluri, Chcetodon,
Sciaenae, Scombri, Pleuronectes, Triglae, Gadi, Mursense, &c. There is not
any appendage to the intestine at the point where its two divisions (when
they exist) communicate, the one portion inosculating with the other in such
a manner as not to leave any cul de sac of sufficient importance to deserve to
be distinguished by any particular name. (Cuvier, Comp. Amt. iii. 471.)
— T r emulator.

simple: in the Frog-fish (Lophius piscatorius) alone,
according to Home, it is divided into two parts by a groove
of no great depth. (Tab. IX. fig. XXI. b. b.*) The most
usual form, however, as it presents itself in the Pike, Bur-
bot, (Gadus lota,) (Tab. IX. fig. XIX.) Sturgeon, (fig.
XX.) Eel, Electric Eel, (fig. XXII.) &c. is that of a blind
sac, which, reascending and lessening in size, terminates
in the intestine by a Pylorus, which is usually not very
much contracted. The structure of the parietes is gene-
rally pretty much the same as in man : the muscular coat
is evident, and frequently very much developed : there are
but few glands : the internal membrane is usually thrown
into many longitudinal folds, particularly at the lower part
of the organ : occasionally, also, there are several trans-
verse folds, giving somewhat the appearance of a reticulated
structure. As instances of peculiarities in the form of the
stomach, I may mention the Conger ( Muraena conger) and
Tetrodon oblongus as described by Cuvier. In the latter
it forms a broad globular swelling, into which the (Eso-
phagus penetrates at its superior extremity, whilst the
intestine commences at the point diametrically opposite.
In the former the blind sac of the stomach turns upwards as
is usual, and contracts to the point of its termination in the
intestine, but has, in addition, at its inferior part a long
appendage terminating in a pointed extremity. The stomach
of Rays and Sharks in general corresponds so closely to the
usual form of the organ in Fishes as not to require any
particular description. In the Squalus maximus (Basking
Shark), however, Home| found a structure differing from
the common in this respect, — that the first or ordinary sto-
mach communicated by a very narrow aperture with a
second roundish and smaller one, which again opened into
the intestine by an equally narrow pylorus. The stomach
f Philos. Trans . 1809, p. 216.

itself contained many stones ; which vve may therefore sup-
pose supply the deficiency of grinding teeth as well as
of the stomacal teeth observed in many Mollusca4

C. Of the Intestine in Fishes.

§. 471. As we have already noticed the shortness of the
alimentary canal generally, and of the intestine itself parti-
cularly, we may at once direct our attention to the blind
appendages so universally found in the vicinity of the
pylorus in Fishes, and so evidently presenting a repetition
of the coeea so frequently found both in Mollusca and In-
sects. (§. 440.) In certain species these appendages are
extremely small, and but few in number; according to
Cuvier there are but two short ones in several species of
Sole (Pleuronectes), and two larger in the Lophius pisca-
torius. (Tab. IX. fig. XXI.) In other instances, on the
contrary, they are extremely numerous, as in the Gym-

| “ Fishes whose food is inclosed in shells have an apparatus for breaking
“ the shells, which is not always placed in the mouth, but sometimes in the
“ stomach, forming a Gizzard similar to that of Birds. This structure is
“ most conspicuous in the stomach of the Mullet : it is confined to the pyloric
“ portion, the muscular coats of which are extremely thick, while those of the
“ cardiac are very thin. It is also met with in the Gillaroo Trout in Ireland,
“ though in a less degree. In that Fish the form of the stomach is exactly
“ the same as in the Salmon and common Trout, only having the coats of
“ the pyloric portion two-thirds thicker. The common Trout lives upon the
“ same kind of food occasionally, and swallows stones for the purpose of
“ assisting in breaking the shells ; so that it is probable that the coats of the
“ pyloric portion in the Irish 'Trout acquire their increased thickness from
“ being more constantly employed in this exertion, in like manner as the
“ Sea-Gull’s gizzard becomes increased in strength after it lias lived seme
“ time upon giuin,” (Home, Comp. Anal. i. 354.) — Translator.

notus electricus (fig. XXII.); of considerable length, as in
the Gad us lota (fig. XIX. t.) ; or consolidated together into
a mass of glandular appearance, as in the Sturgeon. (Fig.
XX. c.) As there is a considerable secretion of mucus
from these blind sacs, and as the secreted fluid is poured out
at the same spot as the pancreatic juice in the superior
animals, we find an additional reason for admitting the cor-
rectness of the opinion already expressed, (§. 440.) that
these organs correspond to the Pancreas of Man.

§. 472. On the other hand these appendages are alto-
gether wanting in many other species, e. g. the Carp, Pike,
Eel, Lamprey, Ray, Shark, &c. : in the two latter, how-
ever, there is another structure of a very singular nature, —
the inner membrane of the intestine being raised in a broad
fold immediately below the stomach, continuing in spiral
turns through the canal, and terminating in the rectum.
This spirally convoluted fold, when examined from below,
has the appearance of arose not full blown. In a Shark
(Squalus maximus) thirty feet six inches long, the stomach
was followed by an expanded portion of intestine, into
which the biliary duct opened. The small intestine was
four feet ten inches long, and furnished with a strong spiral
valve,* (fold of the internal membrane.) That organ ap-
pears to compensate for the shortness of the intestinal canal,
and to impede the too rapid passage of its contents. The re-
gaining part of the course of the intestine is’infinitely various
in the different species, not only as relates to its convolutions,
but also its structure, the internal surface being some-
times furnished with serpentine longitudinal folds, as in the
Eel; at others reticulated, as in the Sturgeon, &c. In
the Pike I find the external membrane of the first half of
the intestine extraordinarily thick, and of nearly cartilagi-
nous consistence. As to the convolutions, they are almost
* Home, Led. on Comp . Anat. p. 391.

wholly wanting’ when the intestine proceeds direct to the an ns,
as in Lampreys, Rays, and Sharks: in most other species
it makes a few turns, which are rarely very serpentine, as,
for instance, in the Sturgeon, (Tab. IX. fig. XX.) the
Burbot, (fig. XVIII.) the Frog-fish, (fig. XXI.), Electric
Eel, (fig. XXII.) &c. In the latter. Home* states that
the rectum reascends towards the stomach, and notices this
fact, together with the position of the anus near the ante-
rior extremity of the body, as a coincidence with the course
of the intestine in several Mollusca, e. g. the Sepise. (§.
442.) In most Fishes the intestinal canal expands at its
posterior extremity, and, in the same manner as in Insects,
(§. 445, where the original character of this structnre
is pointed out,) forms a large intestine, into which the
small intestine frequently projects with a fleshly circular
fold. (See this large intestine in the Burbot, Tab. IX. fig.
XVIII. XIX. 1.) This part of the alimentary canal is
rarely wanting, as is the case in the Carp : in other
instances it is extremely large, as, according to Cuvier,
in the Sparus melops , or furnished with a spiral valve,
as in the Sturgeon. (Fig. XX. d.) In Sharks a hollow
glandular sac opens into the rectum by a little excretory
duct, and is compared by Home to the ink-bag of the
Sepise. This, like many other secretions in the vicinity of
the anus serves to remind us of the original relation existing
between this spot, where indigestible matters are collected,
and the respiratory organ (the apparatus for the volatiliza-
tion of organic materials) — (§. 434. 436. 439.) ; and also
of the connection between the respiratory and secretory
organs, so intimate that the latter appear to be merely
repetitions of the former, a fact which will be still more
evident in considering their history.

* Loc. eil, p. 387.

The rectum of Fishes usually opens by a round anus,
immediately in front of the urinary and genital aperture,
into a longitudinal groove before the anal fin. In Rays
and Sharks this groove is deeper, and has more the appear-
ance of a final expansion (Cloaca) of the intestine, through
which, as through the funnel of the Sepise, are discharged
fceces, ova, semen, and urine. As to the attachment of the
intestine, it is here no longer effected, as in the preceding
Classes, by vessels merely, but by means of a true mesen-
tery. Its laminae which are usually very fine are formed
by a duplicature of the peritoneum, and are reflected either
from the vertebral column, or, when as in the Burbot, the
Swim-bladder is firmly attached to the spine, (fig. XIX.)
from the Swin-bladder itself. The whole intestinal canal,
together with the liver and spleen, is inclosed within the
bag of the peritoneum, which we already found in Snails
and the Sepiae. It lines the abdominal cavity internally,
and in all essential points is organised as in Man. In Rays
and Sharks* however, it has one distinguishing peculiarity,
viz. that a free access of the surrounding medium into its
cavity is permitted by two small openings placed at the
sides of the anus — a peculiarity, the true character of which
we shall hereafter have occasion to examine in connection
with the description of the respiratory and sexual organs.

Section If. Organs of Digestion In the Amphibia.

A. Of the Organs of Mastication, Taste, and Deglutition.

§. 473. It is unnecessary to give any farther description
of the position and external form of the mouth than has
been already done in considering the jaws, which applies
the more accurately as those bones are here not covered by
any great quantity of soft parts, and frequently merely by
the dense, and generally scaly integuments. It is, however,
physiologically important that suction in this, and also in
the following Class, (Humming-Birds excepted,) does not
present itself as the first and simplest mode of conveying
nutritive matter into the alimentary canal. As to the
muscles of the jaws, — the lower jaw is here also raised
principally by a temporal muscle (Tab. XII. fig. II. 36.) ;
it is depressed in a peculiar way, viz. by a muscle corres-
ponding to the Digastric in Man, which, descending from
the back part of the neck, is inserted into the process be-
hind the articulation. (See it in the Crocodile, Tab. XI.
fig. X. i.*) In proportion as this process is drawn up, the
extremity of the Maxillaj- Inferior must be depressed,
(Tab. XII. fig. II. 48.) the articulating process of the
Temporal Bone (§. 184, 191, 203.) forming the centre of

| According to Geoffroy ( A nnalcs du Museum rT Hist. Nat. vol. ii.)
it is not improbable that the Crocodile, as stated by Herodotus, moves the
superior Maxilla (together with the Cranium) rather than the inferior. This
motion, which is possible even in Man, is a natural consequence of the great
length and size of the Lower Jaw. (See Tab. XI. fig. X.)

motion. In Serpents we have also to notice an apparatus
consisting' of several small, muscles, by means of which not
only the bones of the superior maxilla, but also the lateral
branches of the inferior can be approximated or separated,
so as to increase the extent of the aperture of the fauces ;
a motion which appears to be an evident repetition of the
lateral action of the jaws in the Articulata.

§. 474. The teeth of the Amphibia, like the pointed or
hook-shaped teeth generally found in Fishes, are calculated
rather for lacerating and holding than for masticating food.
In form too, they ordinarily coincide with them, being
fixed, as pointed hollow cones, partly to the arches of the
jaws, and partly to the bones of the palate. The succes-
sion of these teeth has been observed chiefly in the Croco-
dile, and is there effected by the formation of new germs
or rudiments within the old teeth, the full number of which,
according to Cuvier, is found in the young animal. The
position of the teeth is not the same in all Amphibia.
They are altogether wanting in Tortoises, the deficiency
being in some degree supplied by a firm horny coating on
both jaws. In the Frog there are very minute teeth in
the Upper Jaw and on the bones of the palate (Tab. XI.
fig. I. d.# fig. III. v.#): in the Salamander there are some
below also. In Serpents, likewise, there are two rows of
teeth on the palate parallel to the edge of the jaw : besides
these, the upper jaw itself is furnished with two fangs in
the poisonous species, and in those which are not so, with
two long rows of teeth; whilst the lower jaw in all is armed
with numerous sharp hook-like teeth, pointing backwards.
(Fig. VII.) The poison fangs are the most remarkable,
on the one hand coinciding in point of structure with the
mandibular hooks of Spiders, (§. 451.) and on the other,
with the teeth of Sharks (§. 463.) as regards their succes-
sion. As to the first point, the venom-fang is provided with

VOL. II. E

a canal opening by a fissure, the poison secreted by a pecir-
liar gland (Tab. XII. fig. III. d.) being propelled through
it by the action of a muscle (fig. III. c.), and thus infused
into the wound inflicted by the tooth. As to the succession
of teeth ; several rudiments are placed in the gum one be-
hind the other, and, according as those in front are lost or
worn away, rise up and become attached to the bone.
Lastly, in Lizards (a few only excepted, as the Iguana,
where there are also teeth on the palate) the teeth are con-
fined to the two jaws as in Rays and Sharks.*

§. 475. In considering the tongue in the Amphibia we
must make a close examination of the different forms pre-
sented by the lingual bone. If for that purpose we turn
our attention to the lingual bone of Fishes, (§. 179.) which
forms almost an integral part of the branchial apparatus,
(§. 164.) we shall, from the forms it there presents, be
better enabled to estimate the true character of those which
occur here. For, in the same manner as the lingual bone
in Fishes presents itself as a bony belt, (like the arches of
the jaws, gills, or ribs, — all equivalent to anterior vertebral
arches,) the rami of which support the lingual cartilage at
the point where they meet in front, — are connected poste-
riorly with the Sternum, and in addition are frequently
beset with repetitions of the branchial arches, (rays of the

* The Cayman has 19 teeth on each side, both in the upper and lower
jaw: in the Crocodile there are 19 above, and only 15 below. In the
Gavial there are 27 above, and 25 below. In the Tupinambis 10 above,
and 13 below. In common Lizards, and in the Iguana, they are sharp and
more or less serrated : in the latter there are 20 on each side, of which
many have six or eight notches. In the Stellio they are t.iangular, and
slightly serrated both anteriorly and posteriorly. The horny substance
covering the jaws of Tortoises is essentially similar to that of the beak of
Birds. Its edges are sometimes merely terminated by an acute angle ; at
others minutely serrated, or divided into large tooth-like processes. (Cuvier,
Comp. And. iii. 199.) — Translator.

branchial membrane,) — so also, in the Amphibia, we find
a middle piece supporting the tongue, and frequently ter-<
minuting in a point ; two large lateral cornua analogous
to the rami of the lingual bone in Fishes, and which in the
same manner have attached to them a point turned back-
wards ; and several smaller cornua analogous to the rays of
the branchial membrane or the arches of the gills.

§. 4-76. Thus, in Frogs, we usually find a quadrangular
cartilaginous lamina with four cornua. (Tab. XIII. fig.
VI. a.) The great lateral rami arise from the front angles
of this lamina in the form of slender cartilaginous threads,
proceed forwards, and then, bending backwards towards
the joints of the jaws, are ultimately attached to the cra-
nium. The smaller posterior cornua are bony, shorter, and
placed at each side of the larynx. In the Surinam Toad
{ Rana pipa )* the body of the lingual bone has only two
small cornua in front, whilst the posterior larger cornua
expand from slender threads into considerable cartilaginous
laminge about an inch long, which are broadest in the female
and longest in the male. In the Salamander, on the con-
trary, the Lingual bone is slender and pointed in front,
whilst the great cornua are separated from the body of the
bone in the form of moveable lateral laminae. (Tab. XIII.
fig. III. a.) In Tortoises, too, according to Cuvier, the
lingual bone appears usually to consist of one broad lamina
with several cornua. The representation given by Meyer
of the lingual bone in the Fresh- water Tortoise has a very
striking resemblance to the lingual bone and branchial
apparatus of Fishes. (Tab. XI. fig. IV. a.) In Serpents,
the lingual bone, when the tongue is small and admits of
being concealed in a sheath, is also very small and shaped
like a ^ ; in the Amphisboena, for instance : — on the con-

* Breyer, Observations Ana/, circa fabric. liana: pipce. Berol. 1811,

p. 14.

E 2

trary, when the tongue can be protruded to a considerable'
extent, the rami of the lingual bone are much elongated
posteriorly; such is the case in most Serpents. In Lizards
we again meet with these various forms : the lingual carti-
lage is sometimes shaped, as Cuvier and I found in the
Gecko; at others, with a point anteriorly penetrating the'
substance of the tongue, and with several lateral cornua,
as in the common Lizard (Lacerta agilis ) ; or lastly, is
furnished with a flat scutiform body and two large lateral
rami, as in the Crocodile. The muscles of the lingual
bone proceed as in Man, partly to the lower jaw, partly
to the tongue, and when it exists, also to the Sternum,
(See in the Frog. Tab. XII. fig. I. 1. 2. 3. 4.)

§. 477. The tongue itself is usually much more com-
pletely formed than in the preceding Class, though still
very imperfect as an organ of taste. In the Frog it forms
a kind of valve, the root of the organ being attached close
to the anterior edge of the lower jaw, and the cloven
extremity turned .towards the opening of the glottis, thus
performing the office of an Epiglottis. (Tab. XII. fig.
XVIII. f.) In the Surinam Toad the tongue is small,
and, as in the Salamander, firmly attached to the floor of
the mouth. In the latter, and also in Tortoises, where
likewise it does not admit of being protruded, it isfurnished
with short satin-like villi ; in the Frog, on the other hand,
it is very soft, smooth, and slimy. Such also, according to
Cuvier, is the case in the Amphisbcense : in the remaining
Serpents, on the contrary, it is distinguished by its length
and mobility. Thus, in a Coluber natrix, thirty-three
inches long, the length of the tongue with its retractor
muscles was 4 inches.; its breadth only about two lines, and
its thickness nearly the same. This long and moveable
tongue, which reminds us of the sucking tube of Insects,
and the proboscis of many Mollusca, is usually vermiform

,<>r nearly cylindrical, — its point being cloven* and coated
with a dark horny covering. It is moved in the following
manner : the membrane lining the mouth is reflected in
front of the aperture of the glottis, so as to form a cylinder
surrounding the lower part of the tongue like a sheath ; to
the root of this sheath are attached two muscles arising
from the long parallel rami of the lingual bone, and, con-
sequently, serving to draw the tongue baek ; another pair,
on the contrary, extends between the same part of the
sheath and the lower jaw, by means of which the tongue
can be protruded. In Lizards, also, the tongue is usually
elongated and cloven ; in the Chameleon it is even suscep-
tible of vermiform motion. In the Crocodile, on the con-
trary, the tongue is so large as to occupy nearly the whole
of the space between the rami of the lower jaw, but at the
same time is immovably attached to the floor of the mouth :
it is covered by a firm membrane with rhomboidal furrows,
and but little calculated for receiving gustatory impressions :
it terminates posteriorly by a small projecting border placed
transversely, and partially covering the aperture of the glottis.

§. 478. In Amphibia, as in most Fishes, the cavities of
the mouth and fauces run almost insensibly into each other,
particularly when, as in Frogs, Serpents, and Tortoises,
the internal apertures of the nares are placed immediately
behind the edge of the jaw. (Tab. XII. fig. XVIII.)
In such instances, as we shall hereafter find, the aperture
of the glottis lies considerably forwards, and there is no
trace ot a Velum Palati. This applies also to several

* This division of the tongue is to he explained only by viewing in it the
fact of the composition of the organ of two lateral halves, which are separate
even in the human foetus : which composition must itself be considered as
a consequence of the separation already remarked in the tongue and lateral
feelers of the Articulata (§. 44-7. 452.), but more paiticularly of the lateral
portions of their jaws.

Lizards, as I found in the Gecko for instance. But in the
Crocodile, where, as already stated, (§. 350.) the internal
aperture of the nares is placed so far backwards, I find in
several small specimens a kind of Velum, though without a
Uvula, by means of which, together with the posterior
raised margin of the tongue, a separation is established
between the mouth and the cavity of the fauces. In
several species of Frogs and Lizards the cavity of the
fauces is much enlarged by an expansion of the skin in
front of the larynx. In the male Frog there are two such
pouches placed one on each side : in the Iguana, Draco,
&c. there is a single one placed inferiorly. These laryn-
geal sacs, as they are called, appear to be receptacles for
air rather than food, for although not connected with the
larynx,* they are extraordinarily distended in rage, &c.
Instead of the branchial openings, which in Fishes w’ere
found at the sides of the cavity of the mouth and fauces,
the CEsophagus is here, as in Man, crossed by the course
of the air from the nasal canal to the aperture of the glottis,
and at the points where we before found the openings of
the gills, we meet in most Amphibia with the orifice of the
Eustachian Tube. But when we shall hereafter have to
remark that true Gills actually exist in some Amphibia,
properly so called, (Siren and Proteus,) and that the Gills
of the Larvae of some other Amphibia are seated in the
Tympanum, f we must consider these facts as throwing
much light on the real character of the Eustachian Tube,
inasmuch as we find that canal, on the one hand, forming a
repetition of the respiratory aperture, on the other present-
ing itself as the primary external auditory passage in the

* According to Cuvif.r, they are connected with the larynx in the
Chameleon only.

f As is the case, according to the remark of Dutrochet. See Meckel’*
ArcJiiv. b. i. h. 1. s. 157.

animal series (§. 363.) ; and lastly, in the superior animals
again forming a canal for the conveyance of air to the
organ of Hearing.

B. Of the (Esophagus and Stomach in the Amphibia.

§. 479. The close connection between this and the
preceding Classes is shewn as well in the structure of these
organs, as in the general proportional shortness of the
intestinal canal. The (Esophagus is a funnel-shaped canal
continued from the fauces, and of smaller diameter : in
consequence of the contraction of the muscular.'jTcoat, the
internal membrane is usually disposed in longitudinal folds.
Its width is nearly uniform with that of the stomach, par-
ticularly in Serpents, in which the whole- intestinal canal,
by its very direct course, approaches closely to that of the
Lampreys. According to Cuvier and Blumenbach, the
CElsophagus in several marine Tortoises (Turtles) is fur-
nished with numerous horny points directed backwards,
like the teeth on the tongue, palate, and pharynx of Fishes,
and apparently serving to prevent the escape of the food
of these otherwise nearly toothless animals. In the Eft,
Home* found a crop-like dilatation of the (Esophagus.

/ §• 480. I he form of the Stomach in the Amphibia is
usually very simple : its glands are but little developed,
and its position is principally on the left side. In Serpents,
as already remarked, it is a direct continuation of the
(Esophagus; in Frogs, Salamanders, (Tab. XIII. fig. III.
b.) and Tortoises, (fig. I. II. b.) it is a simple longitudinal
expansion, which turns upwards, and gradually contracts
into the intestine. HoMEf has described the remarkable

* Led. on Comp. Anal. p. 322. f Loc, cit. p. 327.

thickness of the muscular membrane in a species of Turtle
(Testudo mydas) that lives on vegetable food; where, as
in many other instances, the strength of the coats of the
stomach appears to compensate for the absence of teeth.
According to the same authority, the stomach is nearly
similar in the Siren with two legs, which lives on vegetable
food, and in which the intestine is found to contain little
pebbles to assist in triturating the food : it has also a
horny beak like the Turtle, with two teeth behind it in
each jaw.f In the Pipaf the stomach is divided into two
parts ; of which the first and largest is more than an inch
long, one-tliird of an inch wide, and communicates by a
narrow contraction with the second, which is roundish, and
of the size of a large pea. Such, also, is the case in the
large globular stomach of the Crocodile, (Tab. XII. fig.
XIX. o.) where we find a peculiar distinct portion in the
region of the pylorus, which is close to the cardiac orifice
of the organ. This simplicity in the form of the stomach,
together with the shortness of the alimentary canal gene-
rally, and the coldness of the blood, appear to be the chief
causes of the tardiness of digestion noticed in these animals
by several observers. Thus Home remarked that an Alli-
gator took food but once in several days, and found, as the
animal lived chiefly on birds, that the feathers and other
indigestible parts passed through the alimentary canal.
The fact established by Gruithuisen,|| viz. that the Frog
has the power of completely protruding the stomach through
the mouth, reminds us in a forcible manner of some Zoo-
phytes, (Asterias, §. 434.) in which the food is taken
in a similar manner.^

f Loc. cit. p. 328. \ Breyeu, Obscrvat. Anal. p. 16.

|| Reil’s ArcJiiv.f Physiol, b. viii. h. 2.

«j According to Home, (Comp. Anal. i. 321,) the stomach of the Croco-
dile bears a considerable resemblance to those of birds of prey. It is tole-

C. Of the Intestine in Amphibia.

§. 481. The close resemblance existing between Am-
phibia and Fishes, as regards the stomach, extends like-
wise to the remaining portion of the intestinal canal ; which
is usually placed chiefly on the right side, is short, and but
little convoluted. We almost always find a distinction
between the small and large intestine, the latter being pro-
portionally long and strong. Where the small intestine
is inserted into it, there is a circular projecting fold, or rather
an intussusception. Such is the general disposition of the
parts in Frogs, Salamanders, (Tab. XIII. fig. III. c. d.)
Tortoises, (fig. I. II. c. d.) and Lizards. (Tab. XII. fig.
XIX. r. s. t.) According to Home, however, there is a
long contracted portion in the lower part of the large intes-
tine, and also a little coecum at the insertion of the small,
intestine. Cuvier, also, states, that the inner surface of
the small' intestine in the Egyptian Crocodile is covered
at its upper part with small villi, and inferiorly with a
glandular stratum. The intestine is shortest in Serpents;
where it is usually of less extent than the body, and (in the
Coluber natrix, for instance) runs direct to the anus, the
only indication of the large intestine consisting in the
increased size of the internal longitudinal plicae. On the

rably large for the size of the animal : it is surrounded by a digastric muscle,
as in birds, the middle tendons of which are each about the size of a shilling,
the bellies of the muscle resembling in size those of the gizzard of an Eagle.
The orifice of the pylorus is at a short distance from that of the cardia, and is
extremely small : beyond it is a dilatation, forming a small cavity before the
duodenum begins Translator.

other hand, Home* states that the intestine in the 'Water-
Snake is long1, and much convoluted ; and that there is a
long ccecum in a large African Serpent. Immediately
before the anus the intestine of the Amphibia (as in Rays
and Sharks) forms the Cloaca, as it is called, i. e. a small
expansion, into which open the rectum, urinary and sexual
organs. (Tab. XII. fig. XIX. z. ; Tab. XIII. fig. III. e.)
The anus itself is T shaped in Frogs ; in the Salamander is
a longitudinal fissure with two prominent lips ; and is trans-
verse in Serpents and Lizards.

As to the attachment of the intestinal canal, it is usually
effected, as in Fishes, by means of a delicate mesentery :
as is well known, the transparency of this part, particularly
in Frogs, renders it peculiarly suited for observing the
course of the circulation.f

Section III. Organs of Digestion in Birds.

A. Of the Organs of Mastication , Taste, Suction, and
Deglutition in Birds .

§. 4-82. As the organs of digestion in the Amphibia
approached to those of Fishes, so, also, on the other hand,
the same organs in Birds approximate in a most remarkable
(degree to those of Amphibia. From what has been already

* Home, loc. cit. p. 394.

| In the Iguana and Scincu's, which live on vegetable food, the Intestine
is of considerable length, and is distinguished by the existence of a small
Ccecum at the point where the small enters the large Intestine : such, also, is
the case in the Chameleon. (Home, Comp. Anat. i. .396.) — Translator.

(§. 221 — 224..) said as to the form of the bones of the jaws
in Birds, it will be easy to deduce the shape of the aperture
of the mouth, and of the organs of mastication. The
Bill is formed by two jaws, and being covered with a horny
lamina, nearly resembling that of the claws, constitutes the
organ of prehension, (not mastication,) the influence of the
form of which on every other part of the animal is such
as to render it a most essential element in the formation of
ornithological systems. But, as the most important points
relating to the internal structure and mobility of the two
portions of the bill have been already exposed, and as the
differences in its external form are objects rather for Zoology
than physiological Zootomy, I think it necessary only to
notice some few particulars in the structure of this part, in
which I may add, that we have a very evident repetition of
the beak of the Sepise. On the one hand, we have already
remarked (§. 342.) that the bill for the most part is com-
pletely covered with horn, whilst in others, e. g. the Goose,
Duck, Snipe, it is furnished with a soft membrane, copi-
ously supplied with nerves, which, supplying the place of
lips, must serve as an organ of taste :* on the other, it is
remarkable that not infrequently, e. g. in the Goose and
Duck, Falcon, Shrike, &c. there are either entire rows or
merely single tooth-like projections from the horny cover-
ing of the bill. But as these little teeth are not firmly
fixed to the bones of the jaws, they rather resemble the
tooth-like irregularities on the jaws of Insects than the true
teeth of the higher Classes of Animals.

§. 483. The most remarkable circumstance in the mode
of motion of the two portions of the bill is, that besides
that the lower jaw admits of being drawn away and sepa-
rated from the upper, the latter also has a peculiar motion

* The Cere, also, at the root of the bill in several birds of prey appears to
have a similar character.

its own upon , ami not, as in the Crocodile, (§. 478.)
With , the Cranium. (See §. 220.) As in Amphibia, (§. 473.)
the lower jaw is depressed, chiefly by one or more muscles
(of which the largest and most uniformly present is called
Pyramidalis by Herissant) attached to the process of the
lower jaw behind the articular pit, (Tab. XIV. fig. v. q.)
and to the occiput, (Tab. XV. fig. X. b.) and, conse-
quently, acting upon a lever so as to depress the fore part of
the jaw, and open the bill. It is elevated partly by a large
muscle analogous to the Temporal and Masseter, (Tab. XV.
fig. X. a.) and partly by one or two Pterygoid muscles
arising from the Palate bones. When there is a joint in
the lateral ramus of the lower jaw, as in the Goat-Sucker,
(§. 224.) the Pyramidalis appears to serve the purpose of
expanding, and the Pterygoidei of contracting, that part,
>vhilst both together communicate a certain degree of lateral
piotion to the whole lower jaw. The motion of the upper
jaw is produced partly by muscular action, and partly by
the elasticity of the Nasal and Intermaxillary Bones. (§.
220.) In opening the bill the upper jaw is raised up as by
a lever through the medium of the Zygoma and Palate
Bones acted upon by some muscles attached to the Os
Quadratum : on the other hand, in shutting the bill, when
the Os Quadratum resumes its original position, the upper
jaw is brought down chiefly by the elasticity of the lamina
which forms the sole connection between il and the Cra-
nium. The mechanism of these motions is very curious in
the Cross-bill (Loxia curvirostraj, as described by Town-
son;* where the dissimilar formation of the two rami of the
lower jaw favours a peculiar lateral motion of the two halves
of the bill.

* On the Structure of the Bill of the Crosshcah, in Tracts and Observations
in Natural History* London,. 1799.

§. 484. The lingual bone of Birds (Tab. XVI. fig. I. IL
ill.) is in many respects analogous to that of the Amphibia:
it consists of a long but narrow body, placed parallel to
the vertebral column, its posterior part having attached to
it a long cornu curved upwards on each side. These
Cornua usually consist of an anterior bony, and a posterior
cartilaginous, portions : in the Falcon, however, I find that
the second piece is also bony, and that there is an addition
of a third cartilaginous portion. The course of these cornua
is most remarkable in the Woodpecker; where the long
vermiform tongue reminds us of that of Serpents. (§. 477.)
The cornua of the lingual bone here, like those of Ser-
pents, are long and filiform; are attached at acute angles
to the posterior part of the body of the bone ; run upwards
on each side of the vertebral column ‘along the posterior
surface of the cranium, where they are continued in pecu-
liar grooves to the root of the bill, and are ultimately con-
nected to a canal on the right side of the bill by means of
a tendon, which, however, is double in the first part of its
course. The body of the bone supporting the narrow dart-
like process contained in the tongue is itself nearly filiform,
but has not the posterior straight process usually found in
other instances, as well as in many Fishes and Amphibia.
Iri the Pelican and Spoonbill Cuvier found a flat penta-
gonal shape of the body of the hyoid bone, which reminds
/fis of the flat lingual bone of the Frog.

§• 485. The tongue itself is usually supported by a
bone or cartilage, connected in various modes with the
anterior edge of the body of the lingual bone. In the
Goose, for instance, it is by means of a hinge-like joint ;
where, however, the projection of an anterior and superior
process of the body of the bone prevents any other than
lateral and downward motion of the great lancet-shaped
process entering the tongue. In the Falcon, on the other

hand, where the bone of the tongue is smaller, I find it
divided posteriorly into two rami, between which the body
of the lingual bone is inserted. Several muscles contribute
to the motions of the lingual bone, and of the tongue
itself. The latter is carried forwards by a kind of Genio-
•Hyoideus, the conical shaped muscle of Vico d’Azyr,*
(Tab. XV. fig. X. f.) which turns round the cornu of the
lingual bone, is attached anteriorly to the lower jaw, and
is of great length in the Woodpecker. It is retracted
chiefly by a kind of Stylo-hyoideus, which runs from the
posterior hook-like process of the lower jaw to the lingual
bone (Serpi-hyoideus, fig. X. e.); arid in the Woodpecker
is fixed by a muscle proceeding from the cornu of the lin-
gual bone to the trachea. Besides these there are also
•a Mylo-hyoideus, a Cerato-hyoideus, (fig. X. g.) and a
Thyro-hyoideus. As may be supposed, from the attach-
ments of the bone of the tongue, the latter organ has but
little motion, and but few muscles of its own.

486. The form of the tongue is subject to many
varieties, and presents many approximations to the earlier
formations. Thus the long tube-shaped tongue of Hum-
ming-Birds,!- employed in sucking the juices of flowers, is
a perfect repetition .of the sucking-tube of Beesf and But-
terflies. The dart-shaped, soft, and slimy tongue of Wood-
peckers, of which the anterior part is horny, and the
posterior beset with bristles turned backwards, is also re-
markable; particularly as by the mechanism already described
it can be protruded beyond the bill to the extent of several
inches, in order to seek for insects beneath the bark of
trees. Here, also, as in several Amphibia, we find the

* Memoir es del'Academie des Sciences, 1772, 1773.
f Tiedemann, Zooloyie, th. 2, s. 116.

$ It is to remembered, likewise, that in Bees the elongated Mandibulse
form a sheath for the tongue nearly in the same manner as the two portions
of the Bill in Birds.

tongue sometimes cloven, e. g. in several rapacious Birds,
or even divided into several fringes at the extremity, as in
Thrushes, Starlings, &c. The tongue is also very gene-
rally furnished with sharp points turned backwards, and
resembling the lingual teeth of Fishes. Such is the case
in several aquatic Birds, and to a certain extent at the root
of the tongue in most species. In Parrots the tongue is
particularly soft and fleshy : hence the propriety of con-
sidering it in them as a true organ of taste instead of an
organ of ingestion, as in many other instances.

§. 487. There is not any very absolute distinction between
the cavities of the mouth and fauces in Birds, the Velum
Palati being deficient, and the posterior aperture of the nares,
together with the opening of the glottis, presenting them-
selves as two correspondent longitudinal fissures beset with
papillae. It has been already stated that the two Eustachian
Tubes open into a mucous fossa behind the internal aper-
ture of the nares. In some Birds, too, we find sac-like
expansions of the cavity of the mouth similar to those
already described in several Amphibia. Of that kind is the
great pouch-like dilatation of the floor of the mouth in the
Pelican, as well as the laryngeal sac, which in the Bustard
opens anteriorly below the tongue : according to Tiede-
mann,* the latter exists both in the male and female ; but
according to HoME,f is not found in the young bird. These
dilatations, which in the Amphibia appear to serve for the
reception of an increased quantity of air during the occa-
sional increase of respiration, e. g. in rage, &c. are here
employed rather as receptacles for food or water. In one
species of Heron, however, (Ardea argala ,) according to
Home, there is a laryngeal sac filled solely with air, and
communicating not with the mouth, but with the air-cells-
of the neck.

* Zoologie, b. ii. s. 399. f Led. on Comp. Anal. p. 277.

f>4

ii. Of the (Esophagus and Stomach in Birds.

§. 488. The (Esophagus, which is formed by the gra-
dual contraction of the fauces, by its extraordinary length
in Birds forms a striking contrast with that of the preced-
ing Classes, and is placed in front of the cervical vertebra,
sometimes behind, and sometimes, also, a little to the right
of the trachea. (Tab. XV. fig. XIII. i. hg. XI. a.) The
breadth and extensibility of the (Esophagus are usually
very great, particularly in rapacious and aquatic Birds,
Grallse, &c.; where, as in many Fishes and Amphibia, these
are such as to permit not only the swallowing of entire
animals, but also (at least, in accipitrine Birds) the rejection
of the indigestible parts, feathers, bones, &c. Besides, a
part of the (Esophagus actually supplies the place of a
stomach i for in Herons, Storks, &c. we frequently find
Frogs, &c. partly digested in the stomach, and partly en-
gaged in the (Esophagus.

§. 489. The most remarkable part of the (Esophagus,
however, is its. sac-like appendage, or Crop, (Ingluvies,
Tab. XV. fig. XI. b.) which exists chiefly in granivorous,
but partly also in carnivorous, Birds: in the latter, how-
ever, it appears rather as a uniform expansion of the canal,
and, according to Tiedemann, is wanting only in the
Climbers, Grallas, aquatic, insectivorous, and struthious
birds. It is covered externally by a thin muscular layer,
and lined internally by a mucous membrane with numerous
minute apertures that pour out a copious secretion serving
the purpose of softening the food. If we seek for the true
character of this organ in the history of the developeraent of

«5

the animal series, we shall see cause for identifying it with
the Gill-bag, which, in the inferior Classes, e. g. the
Ascidise, presents itself with the form of a Crop. For, in
the same manner that the origin of a large intestine and
coecum (a Crop of the anal part of the intestinal canal)
was the result of the termination of the intestine in the
respiratory cavity of other species among the inferior
Classes of animals, e. g. the Holothurise and Larvse of
Insects, so also a Crop is produced by the commencement
of the intestine from the same part, as is the case in some
other species. Besides, in several Insects there are similar
appendages to the (Esophagus (§. 457. 458.) ; there, how-
ever, containing air only, and serving as lungs in sucking.
The knowledge, too, of this relation between the dilatation
of the (Esophagus in Birds, and the Gill-sacs and air
receptacles of inferior animals, will prepare us to receive
with less surprise the remarkable fact, observed by Hunter,*
of a milky secretion in the Crop of Pigeons, which takes
place when the young birds are hatched, and is subservient
to their nourishment; inasmuch as there is a most remark-
able connection, as we shall hereafter find, between the
respiratory organs and the generation, as well as nutrition,
of the young.f

§. 490. The Crop is placed in front of the cavity of the
1 horax, resting on the furcular bone and the elastic mem-

1 Observations on -certain parts of ike Animal (Economy. London. 1786.
p. 191.

t In the male of certain species of Bustards, there is a long bag hanging
down on the anterior part of the (Esophagus as low as the middle of the
neck, and communicating with the mouth by an opening under the tongue,
which appears to have a sphincter muscle. In the Ardea argala (Adjutant
Bird), both male and female have a similar bag, which contains air, and can
he filled and emptied at pleasure. In this case, however, the bag does not
communicate with the cavity of the mouth, but with the large air-cells on
the back of the neck. (Home, Led. on Comp. Amt. i, 278.)— Translator.

VOL. II. F

(>G

brane which connects its rami : it is succeeded by a corf-
traction of the (Esophagus ; but soon after its entrance
into the Thorax, the latter again expands and forms a false
or glandular stomach, (Proventriculus, Echinus, — cavitas
cardiaca of Home, Tab. XV. fig. XII. g.) the structure
of which is distinguished from that of the rest of the intes-
tinal canal chiefly by the size and number of its reddish
secretory glands. These glands themselves, as Home has
shewn, are of very various structure in the different species,
being generally simple in the carnivorous, and in the gra-
nivorous and graminivorous, on the contrary, larger and
more complicated. In the latter species, the parietes of
this cavity, which prepares the gastric juice, are thicker, its
glands more numerous, and its whole structure more deve-
loped, though its size is comparatively smaller. On the
other hand, in carnivorous Birds, e. g. Accipitres, Peckers,
and likewise, according* to Tiedemann, in the Pelican,
Cormorant, Spoon-bill, and Ibis, is extraordinarily wide,
short, formed of thin membranes, and more like the sac-
shaped stomach of Fishes and Amphibia: in those instances,
too, the secreting glands are not diffused over the whole sur-
face of the stomach, but congregated in particular situations.

§. 491. In carnivorous Birds, ( e . g. in the Accipitres,
many Waders, and aquatic Birds, Peckers, & c.) this part
terminates insensibly in a second stomach, which is distin-
guished from it chiefly by the absence of the gastric glands,
and by the presence of a muscular stratum, which, arising
from two thin, roundish, tendinous points, appears to serve
the purpose of communicating a rotatory motion to the
contents of the organ.* In the Stork, Spoon-bill, Ibis,

* This kind of motion is proved chiefly by the ejection of rolled masses
from the stomach of rapacious Birds, and, according to Home ( Comp. Anat.
p. 314), by the presence of globular masses of hairs of Caterpillars in the
stomach of the Cuckoo.

Puffin, &c. these two stomachs are separated by a more
decided contraction, and the muscular parietes of the true
stomach are already of considerable thickness (Tab. XV.
fig- V. ) : its muscular structure, however, is most decided
in those Birds which live upon vegetables, for instance,
the Dove, common Fowl, Turkey, Goose, Swan, &c. in
which the muscles form by far the greater part of the
stomach, their bright-red and dense fibres uniting in a very
firm tendinous centre, and as the internal membrane is of
a compact and horny texture, are capable of exerting great
force upon the contents of the organ. Above and below
this Gizzard extends a bag-like expansion where the
parietes of the stomach appear in their original form.
(Tab. XV. fig. XII. p. Tab. XVI. fig. VII.) The Py-
lorus is close to the orifice of the stomach, and does not
possess any valve, by which means the seeds of plants
are enabled to pass into the intestinal canal, a circumstance
of some importance for their diffusion, inasmuch as, accord-
ing to Banks,* they vegetate more quickly under such
circumstances. The situation of the Gizzard in the Bird,
as in Amphibia, is to the left side, below the liver. (Tab.
XV. fig. XI. c.) It is usually found pretty low in the
abdominal cavity, and sometimes very much so, e. g. in
the Cuckoo, lesser Heron, &c.

§. 492. W e thus find that in this Class there is a gra-
dual transition from the uniform membranous stomach to a
more complicated and more muscular structure, reminding
us of the stomach of many species of Insects (§. 455.),
and corresponding to the more perfect developement of the
system of motion in Birds. It has been shewn, also, that
even in Birds of prey this muscular structure may be to a
certain extent developed by a prolonged sustenance on
grain, &c.f It is remarkable, that species which are ex-
* Home, loc. citat. p. 28G. f Home, l. c. p. 271,-

F 2

f>8

ternally similar, differ in the structure of the stomach in a
manner dependent on climate and food, as has been shewn
by Home with regard to the African and the American
Ostrich (Rhea Americana ) : in the former he found a large
cardiac cavity, which bends upwards, and terminates in a
small and very muscular Gizzard (Tab. XVI. fig. VI.) ;
in the latter, the stomach is more capacious, but its coats
are thinner. The action of a Gizzard has been very aptly
compared with that of molar teeth, and if we recollect that
Birds with such stomachs usually swallow stones, &c. so
as to arm it as it were with extraneous teeth, we shall be-
less surprised at the observations of Reaumur, Spallan-
zani, &c. which prove, not only that sharp bodies, as glass*
needles, &c. may be introduced into such stomachs with
impunity, but also that they are speedily crushed and
blunted..

G. Of the Intestine in Bird's.

§. 493. The intestine in Birds proceeds from the stomach
towards the right side, and forms a peculiar longitudinal-
convolution,* between the two portions of which the Pan-
creas is inserted, the inferior of the two returning almost
to the Pylorus. (Tab. XV. fig. XII. ra.) The intestine
itself, particularly in young individuals, is frequently of
considerable thickness in this situation. From this point
the intestine forms numerous convolutions (n), and finally
runs in a straight line along the sacrum to the anus. This
last portion (z. s.) usually has attached to it one or two

• This formation, as we shall hereafter find, depends on the fact, that the
whole of this portion of intestine is external to the abdomen in the Chick.

G 9

coeca, and then increases somewhat in size so as to form a
large intestine, though by no means comparable with the
•size of the same part in most Amphibia. Generally, the
intestine of Birds, by its comparative shortness, approaches
rather to that of the inferior Classes than of Mammalia,
and peculiarly in the carnivorous species. The muscular
parietes are usually of considerable thickness, and the
internal membrane is covered with very long villi in every
part except the eoeca. In several Species, e. g. the Snipe,
Heron, common Fowl, (Tab. XVI. iig. VIII.) there is a
little coecum attached to the small intestine, which is evi-
dently a rudiment of the canal (Ductus vitello-intestinalis)
leading from the yolk-bag to the intestine of the Chick;
for, according to Macartney,* the little yolk-bag itself
never disappears in the Nightingale.f

§. 494. The large intestine or rectum is generally very
short, except in the Ostrich, and is separated from the
small intestine by a kind of valve, only in some granivorous
Birds, e. g. Gallinse. According to TiedemanN,! the
coeca, or rather vermiform appendages, opening into the

* Philos. Trans. 1811, p. 207.

t In the Falco buteo, the villi of ,the internal surface of the intestine are
long and generally cylindrical. In the common Fowl, they are perhaps
longer than in any other animal, at least, in the upper part of the small
intestine. The inner surface of the coeca, near their insertion into the intes-
tine, is here also villous, but only for a short distance, becoming subsequently
perfectly smooth. In the Duck and Goose, particularly the latter, the villi
are very numerous, being found in almost every part of the small and large
intestine, and for some distance upon the coeca. They are mostly cylindrical
or dub-shaped, and terminate by a defined margin at a short distance from
the anus. They are wanting in the King-fisher, Jackdaw, Sparrow, Cross-
beak,. &c. the deficiency being supplied by minute folds of the mucous
merpbrane, which are sometimes disposed in regular zig-zag or serpentine
lines, or transverse lines, mutually intersecting, so as to form a delicate net-
work. (Rudolpiii in Reil’s Archiv. b. iv. s. 347.) Translator.

} Zoofagie, b. iii. s. 456.

rectum present the following- essential differences: they are
particularly long in Birds which live on vegetable food,
e. g. in the common Fowl, Pheasant, Peacock, Turkey,
Goose, and Swan : less so in the Owl, Cuckoo, Crane,
Snipe, Pelican, & c. ; still shorter in the Dove (Tab. XV.
fig. XII. r.), Raven, Thrushes, Finches, &c.; and shortest
of all in diurnal Birds of prey, Titmice, Storks, Gulls, &c.
In Herons, Bitterns, and Divers, there is a single and
almost spirally convoluted coecum like that of the Sepiae.
This organ is entirely wanting in Parrots, Peckers, Hoopoes,
Kings-fishers, Cormorants, Sec. These coeca are usually
smooth internally, somewhat contracted at the point of
communication with the intestine, and for the most part
filled with excrement : the coeca of the Ostrich, however,
have a spiral valve of the same kind as that found in the
small intestine of Rays and Sharks, and the large intestine
of the Sturgeon. As to the nature of these coeca, seeing
that they differ decidedly from the ordinary coeca of other
animals, we may be allowed to enquire if they do not
rather coincide with the gall-vessels, as they are called, of
Insects, which will be hereafter described ? Home* com-
pares them to the secretory organs found in the vicinity of
the anus in many animals, e. g. the ink-bag of the Sepiae.
Oken considers them as representing the angles of the
urinary bladder; but in that case the Allantois (here called
Chorion) should arise from them, and not from the Cloaca.

§. 495. It is remarkable that, according to Perrault,
in the Rectum of the Ostrich there are sacculi formed as
in that of Man, by a bundle of longitudinal fibres. The
mode of its termination is very nearly the same as in the
Amphibia: it is surrounded by a fleshy lip at the point
where it opens into the Cloaca, (Tab. XV. fig. XII. s.
Tab. XVI. fig. X. a.) which presents a cavity, or expan-
* Led. on Comp . Anal. p. 404.

sion, of very various forms in the different species, though
for the most part globular, and serves for the discharge of
foeces, urine, ova, and semen. # This Cloaca is surrounded
by strong muscular fibres, and, as in Lizards, opens exter-
nally by a transversely oval fissure. ( Tab. XV. fig. XI. n.)
This, also, appears to be the fittest place to notice an organ,
the nature of which will come hereafter to be considered in
connection with the progress of the developement of the
young animal, but the functions of which in the full-grown
individual, authorize us in classing it with other glandular
secretory organs about the anus. It consists in a roundish,
but sometimes also longitudinal, sac (Bursa Fabricii), with
thick parietes, placed above the Cloaca, and communicating
with it by a valvular aperture. Its parietes are lubricated
internally by tenacious mucus, and, as remarked by Blu-
menbach, its size appears to increase in proportion to the
age of the animal ; a fact which I have found confirmed
by the examination of the common Fowl, Goose, a young
Heron, &c. (Tab. XVI. fig. IX.) The attachment of
the intestinal canal by the Mesentery, presents nothing
very remarkable in Birds, and as to the parietes of the
air-cells of the abdomen, which here contribute as much as
the Mesentery to determine the position of the intestine,
we shall treat more fully in connection with the respiratory
organs.f
/

1 * According to Cuvier, the position of the penis in the Ostrich is such,

that it can evacuate urine and foeces separately.

f In the Cassowary, the Gizzard is immediately succeeded by two unequal
dilatations of the Intestine, separated from each other by a circular fold.
The parietes of the intestine are then much increased in thickness, until it
dilates into a thin and smooth oval vesicle, imperfectly separated from the
portions of intestine placed above and below it. Its cavity is filled with
green bile, whilst the intestine between it and the pylorus contains nothing
but yellow fluids. Beyond this part the intestine again contracts, its parietes
resuming their thickness and their villous structure internally. The com-

Section IV. Of the Organs of Digestion in Mammalia .

A. Of the Organs of Mastication , Taste , Suction , and

Deglutition .

§. 496. It is a most important repetition of the earlier
formations that in the present Class we find the organs for
the ingestion of nutritive materials of such a kind as to be
capable of serving as organs of suction ; nay more, that in
the earliest periods of life they are exclusively such. This
disposition of them is so general as to have given to the
Class the name it bears : it deserves to be remarked, how-
ever, that suction here is neither performed by the mouth,
lips, and muscles of the pharynx exclusively, as in Zoo-
phytes, Mollusca, Vermes, and some Fishes; nor solely by
the Tongue, as in Insects and some Birds; but that it is
effected by the united action of the lips, muscles of the
cheeks, and tongue, in combination with the respiratory
organs. The various forms of the aperture of the mouth,
which present many and evident approximations to the
human type are sufficiently known as objects of description
in Natural History, and, consequently, I need notice only
the following as of physiological interest. In many Mam-
malia, e.g. Mice, Hares, Bats, Cats, Dogs, Sheep, &c.
there is a fissure in the upper lip extending up to the nose,

mencement of the Rectum is marked internally by a circular fold forming a
kind of valve, a little beyond which the Coeca open into its cavity. The
Rectum is also distinguished by its diameter, which is double that of the
small intestine, by the thinness of its parietes, and by the irregular folds of
its internal viljous surface. (Cuvier, Comp. Anat. iii. 510.) — Translator.

— a proof that the superior maxillary region developed
from the sides of the Cranium like costal arches, is here
less perfectly closed than in other cases, — Man, for instance ;
a fact of which we have already found other examples in
the complete separation of the bony inter-maxilla, (§. 254.)
&e. It is needless to say that a similar fissure presents
itself in Man as a mal-conformation (hare-lip).

§. 497. The mouth of other Mammalia differs from
that of Man by its greater length from before backwards,
and by the greater extent of its aperture ; points in which
it approaches to the bill of Birds and the mouth of Amphibia
and Fishes. This depends upon the breadth of the superior
maxillary bones, (Tab. XVIII. fig. VII. fig. XI. c.) and on
the great length of the jaws as compared with the Cra-
nium: but, as we have already mentioned, (§. 261.) that
the jaws are much smaller in the young animal, it conse-
quently follows that such must also be the case with the
opening of the cavity of the mouth. Such a formation is in
that case the more important, in so far as it tends to facili-
tate the action of suction : nay, in the young of the Opos-
sum, which are so firmly attached by suction within the
abdominal pouch of the mother, the mouth, according to
D’Aboville,* presents itself as a simple round opening,
a sucking aperture. Lastly, I may notice a remarkable
repetition in the shape of the mouth of the Ornithorhynchus
of a formation otherwise peculiar to the preceding Class :
the bill-shaped jaws of that animal are covered, not by true
lips, but by a membrane well supplied with nerves, and,
according to Blumenbach, very similar to that of the bill
of the Duck ; whilst the only thing that can be considered
as a rudiment of true lips is merely a plicated membrane
placed at the root of the bill, and having a relation to it

* Voigt’s Mayazin fur Phjsik, Sfc. b. v. st. 2.

analogous to the membranous ring around the beak of
the Sepise.

§. 498. The mode in which the jaws are armed is very-
various in different instances; and in many presents
recurrences to organizations already described. Some
species, e. g. the Ant-Eaters, like the Sturgeon among
Fishes, have the jaws altogether unarmed ; in others,
as in the Pike and several other Fishes, we find teeth
on the Palate and Tongue, unaccompanied by teeth in
the jaws: thus, according to Home,* the Ornithorhynchus
hystrix has twenty little horny teeth at the root of the
tongue, corresponding to seven rows of similar teeth on the
palate : thirdly, we find teeth on the jaws, though not
-wedged into them, and composed of horny vertical fibres;
thus, in the Ornithorhynchus paradoxus there is in each half
of the jaw one molar tooth, originally composed in the
young animal of two, and two points in the tongue directed
forwards. Fourthly, we find the Palate and superior Max-
illary Bones, in the same manner as the t\vo jaws of
Tortoises, covered with numerous layers of horny laminae
overlapping each other like tiles, the fibres of the laminae
being arranged perpendicularly to them, and unattached at
their inferior extremities ; such is the case in the Whale, f
the laminae of which are well known as affording Whale-
bone.:}:

§. 499, The fifth and most usual mode in which the
* Led. on Comp. Anat. p. 303.

f It is remarkable that, according to Geoffhoy, the young Whale pre-
sents some rudiments of teetli in the lower jaw.

| Although this mass apparently consists of felted hairs, its chemical
composition is distinct, in so far as it is almost devoid of Gelatine, and con-
sists almost wholly of Albumen and Phosphate of Lime. (Home, loc. cit.

p. 200.)

jaws are armed here, as well as in Fishes and Amphibia, is
by Teeth ; and though they here arise from cavities within,
not as in Fishes and Amphibia from the surface of, the jaws,
they do not arise from the bone itself, but are produced in
the form of indurated sheaths or coverings around soft and
vascular papillae (pulps), though neither nerves nor vessels
penetrate into the substance of the tooth itself. The crowns
are first formed, the roots not being produced until a sub-
sequent period, when, by their increase, they protrude
the crowns forward. There are even animals in which the
fangs are in constant course of formation, and where, con-
sequently, the tooth continues to grow like the nails : such
is the case with the tusks of the Elephant, and the incisor
teeth of the Rodentia; which latter, however, are worn
away in an equal proportion.* The teeth in the Cetacea,
however, e. g. the Porpoise, deviate according to Hunter, f
in a remarkable manner from this, which is otherwise the
ordinary mode of their developement in Mammalia; in
them, as in most Fishes, the teeth arise from the surface of
the jaws, and are only received within them as they (the
jaws) increase in size. This mode of developement is pro-
bably influential in obviating the succession of teeth in
these animals, and as a cause why we find them completely
lost in their advanced age.

§. 500. The form, position, and distribution, as well as
the internal structure of the teeth in Mammalia present
infinite varieties in the different species. We shall here,
however, touch only on the most essential points, as they
are sufficiently minutely considered in Natural History as
a mode of arranging Orders and Genera. In Mammalia
as in Man we find cutting, pointed, and flattened teeth ;

* F. Lavagna, Espcricnzi c Biflessioni sopra la carie dei dcnti. Gcmin,
1812.

f TiEDEM Ann’s Zoo/agie, b. i. s. 565.

but in arranging them as Incisors, Canine, and Molar
I eeth, we must also take into consideration their situation,
as it by no means' universally happens that Incisors, for
instance, are actually cutting teeth, or that Molar teeth
have grinding surfaces. As to the Canine teeth, they may
be considered as the remains of the numerous sharp and
conical teeth with which the whole jaw is armed in Fishes and
Amphibia, and even also in several Cetacea, e. g. the Por-
poise. (Tab. XVIII. fig. I.) In both cases they serve the
same purpose of holding and lacerating rather than masti-
cating. They are wanting in many instances, e. g. the
Ruminants with hollow horns, the Rodentia, the Elephant,
the Rhinoceros, and usually in the female of the Solipeda.
In other cases they are present in one jaw only, as in the
Walrus. In general we find them shaped nearly as in
Man, though commonly considerably larger, and that even
in Apes. (Tab. XVIII. fig. XI.) They are largest in the
tusks, as they are called, of Swine: nay, in the Babiroussa,
they project almost like horns above the superior Maxilla,
the tusks passing out laterally through the jaws. In the
Walrus, also, the two solitary tusks of the upper jaw are
of great size.

§. 501. The incisor teeth are rarely altogether wanting,
as in the Ornithorhynchi, Armadilloes, and Sloths ; most
frequently in the upper jaw, as in the Ruminants with
horns and antlers, and less so in the lower jaw, as in the
Elephant, Walrus, Narwhal, and Dugong. (Tab. XVIII.
fig. IV.) They generally coincide pretty accurately in
shape with the cutting teeth of Man ; in other instances,
particularly the Elephant, Narwhal,* and Dugong, they are
remarkable for their size; and in others, again, particularly

* Although we usually find but one of the long and apparently twisted
teeth in this animal, it has really two, though of unequal growth, — the right
ailing out at an early period, whilst the left continues to increase.

the Rodentia, for their curvature and chisel-like cutting'
surfaces. The molar teeth are those which are most uni-
versally found (the Narwhal alone having only its tusks).
They differ in form in a remarkable manner in carnivorous
and graminivorous animals; in the former they are com-
pressed from side to side, (e. g. in the Dog, Cat, Polecat,)
and terminate superiorly in several sharp points, like the
teeth of Sharks ; consequently they are adapted not so much
for masticating as for cutting like scissors, a mode of action
by which they always retain their sharpness. In the true
herbivorous animals, on the contrary, for instance, in the
Elephant, (Tab. XVIII. fig. V.) where each half of the
jaw contains but one, or at most (during the period of
change) but two molar teeth, in the Ruminantia, Solipeda,
and Rodentia, the molar teeth form broad grinding surfaces,
which frequently present transverse furrows corresponding
to ridges on the surfaces of the opposite teeth, so that
leaves, &c. can be crushed and ground by the lateral
motions which are rendered practicable by the flat articular
head of the lower jaw. The molar teeth of omnivorous
animals, e. g. Swine, Apes, and Man, form an interme-
diate gradation between these two opposite forms.*

* The three kinds of teeth, viz. Incisors, Canine, and Molar, are found
in Man ; in all the Quadrumana ; in all the Carnivora ; in all the Pachyder-
mata, except the Two-horned Rhinoceros and the Elephant; in Camels,
Solipeda, and the Ruminants without horns, the Canine being wanting in
(hose with horns, except the Stag, which has vestiges of them. It is only in
Man, however, that the three kinds of teeth are arranged in an uninter-
rupted series, so that those in one jaw every where touch the corresponding
teeth in the other; a fossil Genus of Animals (Anoplotherium) alone resem-
bling him in this respect. In Apes and Carnivora, and in all species where
the Canine are longer than the other teeth, there is at least a vacancy in
each jaw for the Canine tooth of the other. In Bears there is even a con-
siderable space behind each Canine. In Hedgehogs, Shrews, Phalangers,
and the Tarsier, the Canine are shorter than the other teeth, and conse-
quently there is a vacancy between their points on each side. In the

§• 50:2. According' to Home,* the teeth may be divided
into three classes, as regards their intornal structure. 1st,
"W here the Enamel, a crystalline compound of Gelatine and
Phosphate of Lime secreted from the membrane of the
pulp, surrounds the crown and body of the tooth. Of this
hind are the teeth of Man ; of the Carnivora and Omnivora,
as well as the great tusks of the Elephant, &c. where,
however, the coat of Enamel is very thin. 2d , Where the

enamel does not surround the whole of the tooth, and where
the proper dental substance, (a bony mass, the great hard-
ness of which, according to Brande, is owing to the addi-
tion of Carbonate of Lime,) forms a part of the masticating
surface. Such are, for instance, the cutting teeth of the

Makies, the Tarsier excepted, in Bats, the Galeopithecus, and in Camels,
there is a large vacant space between the upper Incisors. The superior
Incisors are wanting in Ruminants, and the inferior in the Walrus. Some
species of Animals lose the Incisors at a certain age ; such are certain
species of Bats, particularly the Phyllostomata and the Sus Ethiopicus.

In other Mammalia there are but two kinds of teeth ; viz. Incisors and Mo-
lares, separated by a vacant space without Canine teeth : such are the, Phas-
colome and all the Rodentia, where there are only two Incisors on each jaw;
of which, however, the superior are double in the Hare ; the Kanguroo,
Nvhich has two below, and six or eight above ; and the Daman, which has
two above and four below. The Elephant has Molares, and two tusks or
Incisors fixed in the Intermaxillary bone, hut no Canine or inferior Incisors.
Others have Molar and Canine teeth with Incisors, e. g. Sloths, and the
Dugong. The Molar teeth being the most essential are the last to disap-
pear, except in the Narwhale. Hence, when there is but one kind of teeth
it is always the Molar, e, g. the Tatus, Ornithorhynchi, Orycteropus, Two-
korned Rhinoceros, and Lamantin. Here, too, may be arranged the Por-
poises, which have uniform conical teeth set around both jaws ; and the
Cachalots, which have similar teeth on the lower jaw alone. In the Nar-
whale the only kind of teeth consists of two tusks lodged in the Intermaxilla,
and of which one is generally wanting. Lastly, the teeth are altogether
wanting in the Ant-Eaters, Pangolins, Echidnas, and Whales. (Cuvier,
Comp, Anat. iii. 151.) — Translator.

* Led, on Comp . Anat p. 1TG.

tcodentia, in which the Enamel covers the anterior outer
surface of the tooth, and consequently by its greater hard-
ness and resistance, as compared with the bony substance
behind it, produces the chisel-like cutting surface : this is
peculiarly evident in the teeth of the Beaver. 3d, To this
head belong those teeth, where, in addition to the Enamel
and dental substance, there is a third, which, according to
the examination of Brande, approaches most closely to the
true osseous texture. Of this kind are the molar teeth of
the Elephant, of several ruminating animals, Rodentia,
&c. In them, a point peculiarly deserving* of remark con-
sists in the complicated manner of the folding of the mem-
brane which serves for the secretion of the Enamel, and the
singular appearances of the layers of Enamel thereby pro-
duced on the masticating surfaces. Thus, in the Ruminants,
the Enamel forms wave-shaped strise penetrating to some
depth : in the African Elephant, it constitutes a row of
rhomboidal laminse Vertical to the grinding surface (Tab*
XVIII. fig. V. b.) : on the contrary, in the Asiatic Ele-
phant, these laminae present parallel waved edges on the
transverse section of the tooth. As the number of these
laminae increases with the age of the tooth, and as the
enamel of each is evidently produced by a distinct mem-
brane, we may in some respects consider each of them as
forming a separate tooth.

( The third substance of these teeth, which forms a kind
of cement, is produced, according to Home, like other flat
bones, by the ossification of the membrane which secretes
the enamel. Cuvier, on the other hand, considers it as a
second secretion from that membrane after it has become"
spongy and thickened, an idea which so far appears some-
what improbable, as that it is not easy to conceive ther
occurrence of two distinct secretions from one and the-
same surface.

§. 503. As to the succession of teeth, in Mammalia
in general, so far as has been observed, it takes place in
the same manner as in Man: i. e. those teeth which first
appear, and which are formed almost at the same time as
the jaws, drop out, and are replaced by others; a pheno-
menon which is to be explained by the elongation of the
jaws, and by the productive power thus re-excited. Thus,
Home* saw in the Wild Boar sixteen primary molar teeth
in both jaws, behind which, and before they fall out, the
jaw is elongated so as to admit the appearance first of one,
and then of a second, large and apparently double molar
tooth. Consequently in the seventh year, when the sixteen
teeth have been replaced, there are twenty-four molar
teeth, and even subsequently to that period the ramus of
the jaw is so much elongated as to permit the formation
of a new cell for the rudiment of another tooth. The
Ruminants, according to Cuvier, shed twelve of their
twenty-four molar teeth. In the Horse the mode of suc-
cession serves the purpose of ascertaining the age up to
the tenth year. At three months the foal has six primary
cutting teeth, and at six months three primary molar teeth,
in each ramus of the jaw. The two middle incisor teeth
are changed at three years, the two next a year, and the
outermost another half year later. The permanent incisors
have a fossa on the cutting surface, which only gradually
disappears as the teeth are worn away, viz. on the two mid-
dle ones in the seventh year, in the eighth on the two next,
and in the two outermost in the ninth year. The canine
teeth first appear in the fourth year, are somewhat blunted
in the seventh, in the tenth completely so, and then appear
longer from the recedence of the gums. The primary
grinding teeth fall out in and after the third year, and are
then replaced by new ones in greater number. There are
* Lect, on Comp, Anat. p. 184.

many remarkable circumstances in the succession of the
teeth in the Elephant : the primary tusks appear about the
seventh or eighth month ; they are about two inches long,
are not hollow, and are shed at the end of a year : the
new ones present themselves at the end of two months ;
are at first black and rough, but subsequently acquire a
polish : in two months time they are an inch long, and at a
later period attain a weight of an hundred and fifty pounds
and upwards. There are eight molar teeth formed in each
side of the jaw, not one by the side of the other, but
behind, or rather above, each other, in such a manner that
a second comes next to the first, which is worn down ; so
that there are two molar teeth in use at the same time.
The teeth which come last, however, have always an
increased number of perpendicular laminae: thus, the first
molar tooth, which is formed soon after birth, has four ;
the next, which is in use in the second year, eight or nine;
the third, twelve or thirteen; the fourth, fifteen; the
seventh and eighth, twenty-two to twenty-three laminae.

§. 504. The varieties in the mode and power of the
motions of the lower jaw in Mammalia have been already
considerably elucidated by what has been said on the shape
of the Zygoma, (§. 257.) on the conformation of the arti-
cular process of the lower jaw, (§. 260.) and on the tem-
poral fossa. (§. 263.) The muscles, which are the imme-
dijite agents in producing these motions, are essentially the
same as in Man, differing only in their relative size, position,
and figure. 1 he 1 emporal muscle is of very considerable
bulk in those cases where the molar teeth are like shears,
e. (]. in the Carnivora, and that even in the smaller ones,
as the Mole. (Tab. XVIII. fig. XIX. a.) In the Her-
bivora, e. (j. the Ruminants, where the molar teeth operate
rather by crushing, it is proportionally small. (Fig. XVI.
6.) The Masseter runs backwards somewhat more obliquely

VOL. II. g

than in Man. (Fig. XIX. fig. XVI. 7.) The Pterygoid
muscles are the chief agents in the lateral motion of the
lower jaw, e. g. in the Ruminants. Besides these, how-
ever, the lower jaw in many Rodentia is partly raised and
partly carried forwards by a muscle extended to it from
the superior Maxillary Bone, and particularly its zygoma-
tic process, — as was first shewn by Meckel. As in Man,
also, the lower jaw is depressed by certain muscles from
the Hyoid Bone ; but more particularly by a muscle cor-
responding to the Digastric, which, however, actually
consists of two bellies in but few instances, e. g. in Apes ;
and, according to Cuvier, is altogether wanting in Ant-
Eaters and Armadilloes.

§. 505. We next come to the description of the lingual
bone, for the form of which that of Man may well serve as
a type. It so far approaches, however, to the earlier for-
mations, that the anterior, and in Man smaller, cornua, in
many Mammalia, e. g. Ruminants, Solipeda, Swine, are
either longer than the posterior, or are composed of two
parts, or are attached to the base of the Cranium by means
of a long and flat bone, not as in Man by a ligament
reaching to the Styloid Process. These flat bones appear
particularly to represent the great cornua of the lingual
bone in Fishes and Amphibia, whilst the greater or poste-
rior cornua rather correspond to those of Birds, as is evi-
dent in the Os Hyoides of the Hare. (Tab. XX. fig. I.
and Tab. XVI. fig. II.) In the Carnivora the anterior
cornua, as well as the bones (Styloid Bones of Cuvier)
connecting them to the Cranium, are distinguished for their
slender and cylindrical shape.*

* In the Echidna hi/strix the body of the Os Hyoides is formed by a flat
straight branch : the extremities of its anterior edge support the anterior
cornua; which are cylindrical, directed forwards, and each composed of a
single piece : the styloid bone descends almost perpendicularly on each side

§. 500. The body of the bone differs from its earlier'
forms chiefly in the absence of the posterior pointed pro-
cess so generally found in Birds, Amphibia, and Fishes ;
and also in the deficiency of an anterior articular surface
for the lingual bone or cartilage, which no longer exists ;
though I find in the Hyoid bone of the Hare and Horse a
process projecting anteriorly, and representing that arti-
culation. The body of the Os Hyoides in the Howling
Ape (Simia seniculus\) is expanded into a large tympanum-
like cavity communicating with the larynx, and very accu-
rately representing the laryngeal sac of the Amphibia,
(§. 476.) which is in the same manner organized for the
reception of air, and for adding to the powers of the voice,
though it is unprovided with bony parietes. We shall
revert to it in treating of the respiratory and vocal organs.^
This bone, too, affords the only instance among Mam-
malia of the solid substance being replaced by cavities for
the reception of air, as in the bones of Birds. (§. 209.)
In Mammalia, as in Man, the muscles of the lingual bone
are tolerably numerous ; but as their course in both in-
stances is essentially the same, a precise indication is

rendered unnecessary, and I will only mention that the

to meet them. The posterior cornua are arched forwards, large, flat, and
articulated to the sides of the body : their extremity, of which the posterior
edge is convex, is connected with a second piece on each side, descending
parallel to the first until it gets behind the body of the bone, where it unites
with the corresponding piece of the opposite side. Two other pieces are
connected with these at the point of their junction, and diverge laterally from
them. (Cuvier, Comp. Anat. iii. 234. ) — Translator.

f And also in the S. Brasilicnsis, according to Wolff. Dc Organo
Vocis Mammulium, pras. Rudolphi, 1812, p. 3.

t In another point of view it might be compared with the bulla ossea of
the organ of hearing in several Mammalia, (§. 247.) as both serve to in-
crease the sound.

G 2

muscle corresponding to the Stylo-hyoideus is scarcely
ever perforated by the tendon of the Digastricus.

§. 507. The tongue of Mammalia is distinguished from
its condition in the preceding Classes, partly by the soft-
ness of its coverings, whereby it is more adapted to the
sense of taste, and partly by the absence of bone or carti-
lage within it, whereby it is rendered less rigid, more
flexible, and fleshy. There is no want, however, of approx-
imations to the earlier formations : thus, the thick, fleshy,
fatty,* and but little moveable tongue of the Cetacea,
which is fixed to the floor of the mouth, and, according to
Cuvier, is without any evident gustatory papillae, repre-
sents the tongue of Fishes : the not uncommon division of
the point of the tongue into two parts, (in the Dromedary,
for instance, but particularly in the Seal, Tab. XX. fig.
V.) reminds us of the tongue of several Amphibia : (§. 477.)
and, lastly, the fringed tongue of certain Birds (§. 486.) is
reproduced in the fimbriated scolloping of the point of the
tongue, as described by Cuvier, in the Opossum. Far-
ther, the vermiform tongue of the Ant-Eater and of the
Echidna (Ornitliorhynckus sive Echidna kystrix) presents
great similarity to the tongue of Serpents, (§. 475.) partly
as regards its shape and motion, and partly in so far as it
appears to serve merely as an organ of ingestion. Lastly,
it is not infrequently armed in the manner described in
Fishes: thus, the prickles with which the tongue of Cats,
and particularly of the Lion, Tiger, &c. is furnished, are
perfectly similar to the lingual teeth of Fishes, consisting
like them of sharp, indurated sheaths, directed backwards,
and seated over soft lingual papillae. (See §. 463, and
Tab. XX. fig. IV.) The lingual teeth of the Echidna
(§. 498.) have been already noticed : but besides this

* }t often affords three barrels of oil in the Whale. See Oken’s Zoo ~
logie, h. ii. s. 667.

animal, we find the tongue of the Vespertilio caninus
powerfully armed, being covered with sharp dentated
scales.*

§. 508. In other Mammalia the covering of the tongue
is usually very similar to that of Man, though the number,
size, and position of the papillse present many varieties.
The shape of the tongue itself is commonly distinguished
from the human by its narrowness, length, and slenderness.
Its motions are ordinarily effected by the same muscular
strata as in Man ; but it is physiologically interesting to
remark that the muscular fibres of the tongue (as an organ
belonging to the Vegetative Sphere) differ from those sub-
servient to Locomotion in being softer and more delicate.
The mechanism of the motions of the vermiform tongue of
the Ant-Eaters and Echidna is veTy peculiar : according to
Cuvier, a long muscle proceeds from the sternum to the
tongue, which, like the longitudinal fibres of the arms of

* Blumenbach fVergl. Anat. s. 338. 2e. Auflage, 1815) observes that he
is not acquainted with any animal in which the tongue exactly resembles that
of Man, for that even in Apes it is distinguished by its narrower and more
elongated form, and by the difference of the various kinds of papillae with
which its upper surface is beset. Thus, in the Simia sylvanus it is three times
longer than it is broad, and has posteriorly only three petiolated papillae
arranged in a triangle ; but, on the contrary, upwards of two hundred
obtuse papillae, situated in front of the former, and at the sides of the Tongue.
Tjr'ey are most numerous at the front of the organ, and appear like white
•granules of various sizes, but altogether vary in appearance from the conical
papillae infinitely more than is the case in Man. In the Opossum the middle
of the anterior extremity of the organ is beset with sharp and firm papillae,
still stronger than those of the Cat Genus : even in the Herbivora there is a
similar disposition, though in a slighter degree, and which is probably of use
in grazing. In the Two-toed Ant-Eater, the tongue, though two inches and
half long, is scarcely thicker at its base than a Crow-quill, and is cylindrical,
with the exception of a superficial groove on its upper surface. At its
root arc two very small foramina cceca: its muscles are very powerful.
(Blumenbach, l. c. p. 341.) — Translator.

the Sepiae, or of the Feelers of Snails, (§. 110. 136.) is
continued into the substance of the organ, and affords the
means of retracting it, and giving it lateral motion ; whilst,
on the other hand, the elongation and other motions of the
tongue are effected by circular fibres that form the exter-
nal stratum of muscle. In the little Ant-Eater (Myrme-
cophaga didaclyla) Blumenbach found the tongue two
inches and half long, though the length of the whole body
is only eight inches. It is probable, also, that the motion
of the long, flat, and narrow tongue of several Carnivora
may be assisted by a round elastic ligament contained
within a sheath, and which, from its worm-like shape, was
once considered as a worm, and as a cause of Rabies
in Dogs. It is best known in the Dog Genus ; where it
lies in the mesial line pretty close to the under surface of
the organ : Blumenbach,* however, found it also in the
Opossum, and I myself met with a perfectly similar liga-
ment, one quarter of an inch long, in the tongue of the
Mole. It appears to me to be nothing more than a rudi-
ment of the lingual cartilage usually found in the preceding
Classes.f

» * Handbuch der Vergleich Anat. s. 335.

f In the Echidna the tongue becomes very slender at the point where it is
detached from the palate, and appears to consist merely of two small and
very much elongated muscular cones placed side by side. Each cone is com-
posed of twojmuscles ; the one external, and formed of an infinite number of
little fibrous bundles, disposed in little rings around the internal muscle, which
diminish in size as they approach to the extremity of the tongue. The first
of these annular fibres are connected with the Genio glossus of the same
side. The internal muscle is cylindrical and very long. It arises from the
upper and front part of the sternum, runs along the front of the neck, and,
passing first between two layers of the Mvlo-glossus, and then between two
portions of the Genio-glossus, penetrates the annular muscle. It consists of
distinct fasciculi twisted in elongated spiral folds. The outermost of these
spiral fasciculi terminate on the first of the rings of the annular muscle :

§. 509. As to the remaining circumstances of the cavities
of the mouth and fauces, the most important consists in the
more perfect separation of the two by means of a Velum,
which generally differs but little from that of Man. Ex-
cept in Apes, the Uvula is commonly though not inva-
riably wanting, inasmuch as I have found it quite evident,
though chiefly membranous, in the Hare. According to
Cuvier, the Velum is remarkable in Cetacea, and also in
the Elephant. In the former it is a tubular elongation of
the posterior aperture of the nares inclosing the pyramidal
projecting larynx, and of importance, as well for the pur-
pose of respiring whilst the cavity of the mouth is filled
with water, as for spouting out the latter. (§. 354.) In the
Elephant, also, the Velum descends below the Epiglottis,
which is consolidated with the Arytenoid cartilages, and
thereby enables the animal to expire when swallowing fluids,
as must necessarily take place when it has previously
sucked them up into the trunk. Some years since I also
observed in the Horse-shoe Bat (Vespertilio ferrum equi
num ) a mode of formation which partly approximates to
that just described, and partly reminds us of the relation
between the posterior nasal apertures and the Rima Glot-
tidis of Birds. (§. 485.) In that instance, instead of the
Velum the posterior aperture of the nasal canal has attached
to it a membranous projecting border, which corresponds
•vyith the utmost precision to a similar border surrounding
the opening of the Larynx, and elongated anteriorly in
the form of an Epiglottis. (Tab. XIX. fig. XIX. b.)
Nay, even in the Rodentia we find this hitherto unnoticed

the subjacent fasciculi reach the succeeding rings, and so on, the innermost
extending to the extremity of the tongue ; the diameter of the latter dimi-
nishing in proportion as the fasciculi reach the point of their insertion. It
will easily be seen how the organ can be shortened and twisted in various direc-
tions by the longitudinal muscles, whilst the annular fibres, on the contrary,
serve to elongate it. (Cuvier, Comp. Anat. iii. 264.) Translator ,

repetition of a simple posterior nasal aperture ; thus, in the
Rat for example, I observe on the roof of the fauces
merely an oval hole leading to the nares without any
Velum.*

§. 51 0. The Pharynx in this Class is characterized by
powerful strata of muscular fibres, the arrangement of
which, however, present but few important variations from
the structure of the same part in Man. The greatest
peculiarity is found in the Cetacea, where it is elongated
superiorly into two fleshy tubes serving to conduct the
water into the canals and pouches belonging to the nose.
In this Class also, as in Amphibia and Fishes, we occa-
sionally find sac-like appendages to the cavity of the mouth,
which are chiefly employed as pouches for containing food;
but also, in some Bats, the Genus Nycteris, according to
GEOFFROY,f appear very evidently to serve as receptacles
for air : for, as these animals are provided at each side of
the mouth with an aperture leading between the skin and
the muscles of the body, they are enabled, whilst the nasal

* In the Carnel the Vehim Palati descends very low; and instead of
Tonsils there are numerous little depressions, containing greenish concretions,
probably salivary calculi. In front of the Velum Palati is a peculiar organ,
the true nature of which is but little understood : it consists of a depending
membrane, eight inches long by fouF inches wide, apparently formed by two
laminae of the mucous membrane connected by cellular substance, and fur-
nished with muscular fibres that are probably capable of voluntary motion : its
surface is perforated by the oblique orifices of numerous foveoli. It is stated
that during inspiration air penetrates jt and distends its cells, though the
ipode in which this can take place is not very obvious, unless it be by means
of a large excavation on each side, described as being capable of admitting the
top of the finger. (Richter on the Anatomy of the Camel. Seethe Edinb.
Journ. of Med. Science, vol. i. 221.) The same organ has been noticed by
Sir E. Home, in the life of Hunter, ( Treatise on Inflammation!, &c.) who
describes it as a pouch or bag, and attributes to it the office of moistening the
fauces— Translator.

f Annales clu Museum d'llist. Nat. vol. xx. p. Id.

canal is closed by a peculiar mechanism, to propel the exr
pired air beneath the skin, so as to expand it and facilitate
their flight. As to the true Cheek-pouches, they form, in
the Hamster for instance, two spacious sacs about 2-g- inches
in diameter, placed beneath the skin at the sides of the
joint of the jaw, are lined internally by the membrane of
the mouth, and covered externally by a muscular membrane
which is connected with the spinous processes of the cer-
vical vertebrae. There are similar cheek-pouches in the
Ornithorhynchus, in Baboons, Cynocephali, and Monkeys,
(Cercopitheci.) In some degree they perform the same
office as the Crop in Birds. Here, also, we must notice
the glandular sac which is formed at the posterior part of
the palate in the Camel,* though, like the mucous fossa
on the palate of Birds, it appears to serve rather as a
secreting organ than as a receptacle.

B. Of the (Esophagus and Stomach in Mammalia.

§. 511. The (Esophagus of Mammalia differs from that
of the preceding Classes, as well by its smaller size, as by
the greater strength of its fleshy parietes. The latter cir-
cumstance is more particularly evident in the (Esophagus
of the Ruminants, which is susceptible of voluntary motion,
and in which the muscular fibres are distinguished by their
bright red colour from those of the rest of the alimentary
canal. In them, as well as in many other Mammalia,
these fibres are for the most part disposed in two spirally
contorted and mutually decussating sets, an arrangement by
which their powers of action must be increased. The
* IIomi;, quoted by Blumenbacii ( Ilandbuch , s. 121).

internal membrane which usually forms longitudinal, and
more rarely, transverse folds, is remarkable in many species,
e. g. Dogs, Moles, and Beavers, for its very great density,
and the evident approximation in its properties to the ex-
ternal epidermis, differing in this respect from the human
(Esophagus, with which it otherwise corresponds closely,
as well in position as in its general form. We may remark,
as an unusual structure of the (Esophagus, a peculiar valve,
observed by Home, at its commencement in the Echidna
(Ornithorhynchus hystrix), together with numerous papillae
at its termination, pointing upwards, and resembling a
similar structure in some Tortoises. (§. 479.) In beasts
of prey and most Palmata, also, it reminds us of the earlier
formations by its very considerable width.

§. 512. Among the numerous variations presented by
the form of the Stomach in Mammalia, it is peculiarly
interesting to trace the gradual transition from a simple
organization, similar to that of Fishes and Amphibia, into
one of a more complicated kind, such as we have hitherto
found only in Mollusca and Insects. As the Stomach of
Man is to be classed among the more simple of those found
in Mammalia, I may state generally that the structure,
position, and form, are very similar in those of most of the
Carnivora, e. g. Dogs, Cats, Martins, Moles, Bears, and
Hedge-hogs, as well as in those which live on insects,
fruits, & c. e. g. Apes, Bats, Squirrels, &c. ; and only differ
from it, either, as in Bears, Lions, by a somewhat more
evident contraction and division into two halves, at least
during life, and more particularly the period of digestion ;
or, by a more elongated form, as in the Martin ; or, lastly,
by a more spherical shape, as in several Apes and Bats.
The stomach of the amphibious Mammalia, e. g. the Seal
and Manati, deserves particular notice, in which there is
a similarity to that of Fishes, dependent on the deficiency

of the left or cardiac pouch of the organ, and the insertion
of the (Esophagus at the extreme left margin. (Tab. XX.
tig. III.) The Stomach of the Ant-Eaters and Armadilloes
is likewise simple, but as they have no teeth, like Birds, it
is very muscular, and stones are swallowed for the purpose
of crushing the food. According to Home, the stomach of
the Ornitliorhynchus is proportionally very small and its
structure simple : the (Esophagus gradually expands into
a sac attached to it, and opens close to the pylorus. The
glands secreting the gastric fluid are in general more
evident than in Man. The epidermis of the (Esophagus
usually terminates at the orifice of the stomach.

§. 513. The Stomach of several of the Roden tia forms
an evident transition to the more complicated formations,
partly by the greater developement of the glands in the
region of the cardiac orifice, which in itself is also an
approximation to the cardiac cavity of Birds ; and partly
by the more strongly marked muscular contraction of a
portion of its parietes. The Stomach of the Beaver may
serve as a specimen of this kind, in which the epidermis of
the (Esophagus terminates abruptly at the cardiac orifice,
(Tab. XIX. fig. XV. a.) whilst there is a glandular body
external to the same spot, over which the longitudinal fibres
of the muscular coat are continued. (Fig. XIV. c.) When
these fibres are removed, we find a collection of little
mticous pouches, the ducts from which gradually unite
together, and ultimately terminate by several apertures of
different sizes and closed by semilunar valves. ( Fig. XV.
b. b.) There is likewise a considerable contraction of the
parietes near the Pylorus, giving rise to a second and
smaller gastric cavity. (Fig. XIV. f.) According to
Home,* there is a similar glandular apparatus in the
Stomach of the Wombat; and in the Dormouse it even
* Led. on Comp. Anal. p. 146.

forms a peculiar cavity, covered with glands, and placed
at the cardiac orifice. Of this kind are also the Stomachs
of Hares and Rabbits, in which it is already easy to recog-
nise the distinct functions of the two portions of the organ,
the food contained in the left being merely softened, whilst
that in the right is found actually digested. The separa-
tion of the two halves of the Stomach is likewise very
evident in the Hamster (fig. XVIII.) and the Water-Rat,
where the first portion is lined by the epidermis of the
(Esophagus, as though it were a Crop, whilst in the Hare,
on the contrary, it terminates absolutely at the cardiac
orifice.

(

§. 514. The more complicated form of the Stomach is
still farther developed in the herbivorous Mammalia. The
three divisions, which are but imperfectly indicated in the
common Rat (Tab. XX. fig. VI. a.), present themselves
in the Porcupine as three separate cavities, although the
cardiac orifice and pylorus are still pretty close together.
In the great Kanguroo, the length of the stomach, and its
numerous pouch-like appendages, give it the appearance of
a portion of the large intestine in Man. The gastric glands
are collected into separate roundish masses; the cardiac
orifice is at a considerable distance from the pylorus, and
the size of the left cul-de-sac is far inferior to that of the
larger division to the rights according to Home,* also,
these animals are capable of ruminating when fed upon
hard food. Amongst Bats, the Vampyre (Vespertilio
caninus ), which feeds only on buds and flowers, and not by
sucking blood, approaches most to the Kanguroo in the
intestine-like shape of its stomach. Amongst hoofed
animals, the Solipeda offer a more simple form ot stomach ;
the two portions of which it is composed are, however,
distinguished by their lining membranes ; that of the left
* Led. on Comji. Anal. p. 157.

93?

being continuous with the epidermis of the (Esophagus.
In the Pachydermata the stomach is already provided with
some considerable appendages. In the Pig, the large base
of the stomach is turned to the left side, and furnished,
with a sac-shaped appendage, whilst there is a fleshy conical
process in the pyloric half that may serve occasionally to
close the orifice. In the Elephant, the stomach is more
cylindrical, and has likewise a conical appendage to the
cardiac portion, separated from the rest of the organ by
strong transverse folds. These appendages are still more
considerable in the Peccari (Sus tajassu) and Hippopotamus,
in the first of which the cardiac extremity is provided with
two, and in the second with three large sac-shaped expan-
sions, which have no claim to be considered as distinct
stomachs, inasmuch as the structure of the lining membrane
is the same in all. To this series, too, belongs the stomach
of the Sloth (Bradypus), which, according to Daubenton
and Cuvier, consists of a large globular cardiac extremity
with an extensive appendage, connected to it, and commu-
nicating by a canal with the narrow gut-like pyloric por-
tion, which is also enlarged by a small cul-de-sac opening
into it.*

* In the Kangaroo Hat, the Stomach is divided into two gut-like sacs,
united nearly at right angles, and communicating together by a large aperture.
The cardia enters at the point of union of the two sacs, hut corresponds
rtfore particularly to the first ; a fold, however, is stretched from the (Eso-
phagus into the second, and probably serves under certain circumstances to
guide the food directly into it. The second sac is elongated, and divided
into several small sacculi, by the contractions of its pariet-es. Its right
margin, which is thick and short, fixes these sacculi by a muscular band like
that of a Colon. A long and narrow gland is stretched along it, and secretes
a fluid which enters the stomach by several small orifices on its inner surface.
The posterior half of the left sac is disposed in large longitudinal folds, whilst
there are merely superficial folds intersecting each other so as leave polygonal
interspaces upon the anterior half, and upon the commencement of the right
sac, whilst the greater part of the surface of the latter is perfectly smooth ;

§. 515. We next come to the description of the sto-
mach in ruminating Mammalia, in which, and in certain

so, that from the difference in their structure the two sacs might, perhaps,
with propriety, be considered as distinct stomachs. The muscular membrane
forms a decided circle around the Pylorus, and helps to distinguish the
Stomach from the Duodenum.

In the great Kanguroo, the Stomach has but a single cavity, forming a
long and large cylinder, curved in various directions, and occupying a great
part of the abdomen. It has several large muscular bands like those of a
Colon, extending through its whole length, and dividing it into sacculi.
The part of the cavity which is situated on the left of the Cardia, has two
curved appendices crossing it at right angles, and is not more than a sixth part
as long as the left division, an inverse proportion to what is observed in the
Kanguroo Rat. The left pouch bifurcates into two small cul-de-sacs, of
which the outermost is distinguished by its thick and glandular parietes,
whilst the inner surface of the other, and of the rest of the left sac, is smooth,
whitish, and disposed in small irregular folds. This appearance of the inner
membrane is continued around the Cardia, and extends, in the form of three
long triangular bands, into the right pouch, whilst the rest of its surface is
greyish, semi-transparent, smooth, and not plicated. The Pylorus has a
circular fold of muscular fibres, and a corresponding ring of glandular struc-
ture on the inner membrane, by which the diameter of the opening is much
reduced.

In the Roussette, which is frugivorous, the (Esophagus opens into a
rounded sac, separated by a deep groove both from the right and left pouches
of the Stomach. The left cul-de-sac is cylindrical, terminates in an obtuse
point turned backwards, and is covered by very thick muscular fibres. The
right extremity of the organ is 2^4 times as long as the left, forming a large
tube with thin parietes, and with several contractions, which give it a saccu-
lated appearance like a Colon. The Pylorus is furnished with a valve
closing it so perfectly, that it does not admit the passage of air through it.

In the Unau, or Two-toed Sloth, the Stomach is double. The first
cavity is very large and not rounded : it contracts posteriorly, and is elon-
gated into a conical appendage which is twisted from left to right, its cavity
being separated from that of the Stomach by a semilunar fold at its base
The Cardia opens quite to the right side of the Stomach, and leaves a vast
cul-de-sac to the left: it leads into a canal which at first passes from before
backwards along the right side of the first stomach. The right margin of
the canal is continued still farther in the same direction, expanding conside-
rably, and separates the left pouch of the Stomach from the cavity between

Cetacea, it appears in its most complicated form. In the
Ruminants with horns or antlers, as is well known, there
are four stomachs, though, as it appears to me, the three
first, which are lined by a continuation of the epidermis of
the (Esophagus, should be considered merely as separate
portions of the left or cardiac extremity ; and chiefly, be-
cause, like that portion in other animals, — probably, accord-
ing to Home’s investigations, even in Man, — their operation
is that of preparing the food for the digestion which is
accomplished in the fourth or pyloric stomach, corresponding
to the stomach as it exists in other animals. The different
stomachs are arranged in the following order: on the left
side, and close to the cardiac orifice, is a large cavity, usually
rather globular, frequently divided with distinct pouches,

it and the conical appendage. The canal then bends from left to right, and
enters the second Stomach by a very small orifice which corresponds to the
extreme right margin of the first Stomach. The inner membrane of the
canal is white, tendinous, and arranged in longitudinal folds. The second
stomach is shaped like an Intestine, is much smaller than the first, and
bends under it from right to left. A semilunar fold divides it into two
portions, the first of which has very thin parietes, whilst those of the second
are thicker, particularly around the narrow aperture of the Pylorus. The
first of the two portions of this second Stomach appears to be again subdi-
vided, by a little fold with a dentated margin, into two parts, of which the first
communicates with a little cul-de-sac placed in front of the right extremity of
the first, between two similar sacs, opening by a common orifice into the
first Stomach. These three little sacs are polygonal, and their parietes
apparently glandular. 1 he internal membrane of the two Stomachs is
smooth, but not villous, and has even a tendinous appearance in the first
two sacs of the great stomach.

In the Ai (Three-toed Sloth), the appendix of the second Stomach is
much more elongated, and is divided into three sacs by two longitudinal
septa. The existence of a canal, like that in the Stomach of Ruminants,
and permitting the passage of food direct from the (Esophagus to the second
Stomach, suggests the idea that a kind of rumination takes place in these
ammuls. The contents of these stomachs consist of ligneous matter in the
state of plaster. (Cuvier, Comp. Anat. iii. 375, 378, 389 Translator.

serving for the first reception of the food, and known by*
the name of Paunch. (koiXix i/.cyxXv>; rumen; penula$
ingluvies ; magnus venter ; Pansen or Wanst. Germ. ;
l’Herbier; la Double. Fr. Tab. XIX. fig. XIII. b.) It
is lined internally with a somewhat rough membrane pre-
senting many flattened papillae, and is constantly found
filled with food in rather a dry state.* The rotatory motion
that takes place within it is proved by the balls of hair or
woody fibres, which, when coated over by a firm crust, form
concretions consisting of concentric layers. These are
known by the name of Bezoar stones, iEgagropilse, &c. ;
are usually found in this cavity; less frequently in other
animals, for instance in the stomach of the Horse ; and
resemble the rolled masses of indigestible substances
ejected from the stomachs of Birds of prey.f

§. 516. This first spacious stomach is succeeded by a
second very small one, the internal membrane of which is
likewise coarse, beset with little papillse, and folded into
numerous irregular polygonal cells dentated at the edges
of their orifices. (Tab. XIX. fig. XIII. c.) It is called
the Honeycomb Bag. (K^wpaAos; reticulum; Garn or
Haube. Gem.; le Bonnet. Fr.) It is placed immediately
below the entrance of the (Esophagus, and appears to
serve more particularly for the reception of fluids, and
during rumination for moistening the small portions of food
which are successively propelled from it into the mouth. %

* Home fotmd it half full even in an Ox that had fasted 7 days. ( Led ’
on Comp. Anat. p. 174.)

f Blumenbach mentions an instance in which a hall of this hind Was
vomited up by a Cow. ( Handbuch dcr Verglcicli. Anat. s. 126.)

| May we not here refer to many Mollnsca and Insects, in which the
second stomach, e. g. in the Aplysia, (§. 440.) is provided with grinding-
teeth ? Nay, we find something similar even in Birds, in which the food is
softened in the Crop, or in the cardiac cavity, and then crushed in the
Gizzard.

The third stomach is lined by broad but thin and rather
coarse membranous folds, ranged lengthwise, from which
circumstance it has obtained the names Many-Plies;

centipellio ; erinaceus ; Buclis, Psalters, Germ. ;
le Feuillet, Fr. (Tab. XIX. fig. XIII. d.) It receives
the food after it has been chewed the second time ; and it
is remarkable, that, according to Davy and Brande, it is
distinguished by the evolution of Hydrogen gas within it.*
Lastly, the fourth stomach, which we have compared to
the pyloric portion in other animals, is lined by a soft
mucous membrane ; is of a longitudinal, gut-like shape ; is
connected with the preceding one by a very narrow orifice;
and from the peculiar property which its secretion possesses
of coagulating milk, is called the Rennet-bag (the Red);
eyus-fov ; abomasum, faliscus ; Labmagen, Rohm, Germ. ; la
Caillette, Fr. (Fig. XIII. e.)

§. 517. The organization of these stomachs is peculiarly
remarkable, not merely as it is subservient to rumination,
but also as it affords the means of carrying the food after it
has been ruminated directly into the third, without passing
again through the two first cavities. I have already called
attention (§.511.) to the great strength of the muscular
fibres of the (Esophagus in these animals, and have here
to add, that the same structure is continued by means of a
groove, which may be considered as an elongation of the
(Esophagus, into the third stomach, the intermediate space
occupied by the second being very inconsiderable. The
first and second stomachs are to be considered as appen-
dages going off from this groove ; and as its edges can be
brought into contact by its muscular power, the morsel of
food must necessarily be conveyed at such times into
the third stomach. Nay, in young animals, whilst still
suckled, when the stomach is distinguished by the incon-
* Home, Led. on Comp, Anat. p. 17t,

VOL. II.

siderable size of the Paunch,* the milk appears to pas*'
direct even into the fourth cavity, the laminse of the third
still adhering closely together.

§. 518. The organization of the stomach is still more
complicated in the Ruminants without horns, i. e. in the
Camel, Dromedary, and Lama. As to the former, its
stomachs, according to Daubenton and Home, are distin-
guished from the form of the ruminating stomach, as already
described, by two cellular appendages to the first cavity,
and by a peculiar musculo-cellular structure of the second.
The fluids, which these animals take at distant intervals,
though in large quantities,-]- here also pass into the second
stomach (Honeycomb Bag) : the cells of that cavity are
about an inch in diameter, are interwoven with numerous
muscular fibres, and thereby acquire the power of contract-
ing and closing their orifices so as to retain water without
allowing it to be contaminated by intermixture with the
other contents of the stomach, even during the repassage
of the ruminated food. A smaller quantity of water passes
into the cellular appendages of the Paunch, or first stomach,
and serves to moisten the food contained in it as much as is
necessary to fit it for being returned to the mouth for rumi-
nation. When the morsel is swallowed for the second time,
it passes through the second cavity, the cells of which are
closed, into the third, which is extremely small, and almost
perfectly smooth on its internal surface, and from that into
the fourth. The latter is gut-like, is partly beset with
numerous longitudinal folds, and apparently divided into
two portions, which Daubenton considered as similar to
the third and fourth stomachs of the horned Ruminants.

* In a foetal Calf of four or five months I found the cavity of the Paunch
filled by a peculiar thickish, gelatinous fluid.

■f Home {Joe. cit.) mentions that a Game) observed by him drank but
once every two days, but then to the amount of 6 or 7 1 4 gallons at once.

§. 519. In tlie Cetacea, lastly, we meet with a form of
stomach very closely connected with its structure in the
Ruminants. Thus, in a Bottle-nose Porpoise, eleven feet
long1, Home* found the (Esophagus wide, and furnished
with longitudinal plicre, passing directly into a spacious
cardiac cavity, fifteen inches long and nine broad, with
strong parietes, and lined internally by a continuation of
the epidermis of the (Esophagus. As in the Ruminants, so
here, this cavity serves to receive and soften the food; and
as these animals live chiefly on fish, &c. we find that not
merely is the flesh separated from the bones within this
cavity, but that even the earthy matter is dissolved, and the
bones themselves converted into a gelatinous mass, probably
through the medium of a more powerful secretion supplying
the place of rumination.-]- A canal, three inches in length,
leads from the first stomach to the second, in which it ter-
minates by an aperture two inches and half in diameter, at
which point the epidermis ceases. The second stomach is
seven inches in diameter, globular and cellular, and com-
municates with the third smaller stomach by an orifice
only five-eighths of an inch in diameter. The narrowness of
the communications between the stomachs appears chiefly
intended to prevent the passage of undissolved bones, &c.
into the fourth. This, which communicates with the third
by an opening less than three-eighths of an inch across, is
cylindrical, is fourteen inches and half long, three broad,
smooth internally, and, like the corresponding stomach in
Ruminants, the true seat of digestion. Even the pyloric
orifice is but a quarter of an inch in diameter. In other
species there are frequently one or two additional cavities.

* Loc. cit. p. 253. ,

f It is a singular fact, affording an unexpected coincidence withihis cir-
cumstance, that ruminating animals are capable of subsisting on Fish ; e. g.
Oxen in the North of Asia. (See Home, Op. citat.)

H 2

100

C. Of the Intestinal Canal in Mammalia.

§. 520. Various attempts have been made to reduce t&
some generally applicable principles, the extraordinarily
numerous varieties presented by the organization of the
intestinal canal in the different species of this Class, either
by a reference to modes of life, or a comparison of the
length and width of its different portions ; but the excep-
tions have invariably proved too numerous to admit of the
establishment of any such rules. If, for instance, it should
be assumed as a general principle, that herbivorous Mam-
malia have a long, and Carnivora a short, intestinal canal,
it would be in absolute contradiction to the fact that, in the
Sloths, which live wholly on vegetables, and in several
Makis, Mice, Shrews, &c. which live chiefly on fruits, &c.
the intestine is unusually short, i. e. 3 or 4 times the length
of the body ; whilst, on the contrary, it is found of extraor-
dinary length, (from 11 to 28 times as long as the body,) in
many species that live solely on animal food, e. g. Seals*
Porpoises, &c. So also, in the Lion for instance, where
the canal is little more than three times the length of the
body, we find it very narrow, instead of being wide as we
might expect. In general, it appears to me that the cir-
cumstances of the intestinal canal depend chiefly on the
situation occupied by the individual in the series of animals,
and more particularly that the selection of food must depend
on the organization of the alimentary canal, and general
structure of the animal, rather than that any peculiar
mode of nutrition influences the organization. Thus, short-
ness of the alimentary canal appears to render rapid assimi-
lation, and consequently highly nutritive, i. e. animal, food

101

necessary : a necessity which is still farther augmented, if
the animal should be at the same time distinguished by the
energy of its muscular powers. On the other hand, length
and a more complicated structure of the alimentary canal,
in other words, a decided developement of the vegetative
organs, appear to determine the subsistence of the animal
on vegetable food.*

§. 521. The character of the Intestine, nay, even of
the entire alimentary canal, in Mammalia being determined
principally by their relative positions in the animal series,
we sliall be enabled to recognise a connection, as regards
the structure of those organs, between the animals of the
preceding Class and those which approach most closely to
them in the present. If, in the first place, we assume, as
a. standard for comparison, the circumstances of the human

* Many of the apparent anomalies in the length of the intestinal canal in
different species of Mammalia, admit of being explained by the degree of
complication of the structure, not only of the Intestine, properly so called,
but also of the Stomach and of the Coeca, and similar organs appended to
the canal, as well as by the relative diameter of the canal, the absence or
presence of the various kinds of teeth, & c. Thus, in the Makies, for in-
stance, which are truly frugivorous, the alimentary canal is comparatively
shorter than in Apes, a deficiency more than compensated by the great deve-
lopement of the Ccecum. In the Plantigrada, the deficiency in the Coecum
and large Intestine, together with the uniformity of surface and small
dityheter of the canal, detract considerably from the effect of its length. In
Rodentia, the Ccecum, which is highly developed, and in the Tardigrada, the
very complicated structure of the Stomach, place these animals more nearly
on a par vvith other herbivorous species than .might at first be supposed.
These considerations, however, tend to place in a still stronger light the
contrast between the truly carnivorous animals, where every circumstance is
combined to accelerate the passage of their highly nutritive food through the
intestinal canal, and the Ruminants, &c. the most strictly herbivorous, in
which the structure of Teeth, Stomach, and Intestines, reaches the highest
degree of complicity, evidently for the purpose of extracting, or rather pre-
paring, the greatest quantity of nutriment from substances least calculated to
afford it — Translator.

102

intestinal canal as regards its length, (which in the adult is
to the body as 5j to 1, and in the child as 7 or 8 to 1,) its
position, and its division into small and large intestine, we
shall find the following principal variations in the different
species. In the amphibious Mammalia, the relation to
Fishes (in which the vegetative organs so remarkably pre-
ponderate, and where the abdomen occupies the whole of
the body,) displays itself in the peculiar developement of
the organs subservient to the assimilative processes : here,
however, the mode of this developement consists in the
length of the intestine, and not, as in Fishes, in the breadth
of the alimentary canal, and size of the abdomen. In the
same manner as we found the stomach extremely compli-
cated in some of these species,* so also is the intestine dis-
tinguished by its remarkable length ; being, in the Porpoise,
according to Cuvier, 11 times, — in the Bottle-nose
Whale, according to Home, 15 times, — and in the Seal,
according to Cuvier, 28 times as long as the body.
In the Porpoise, as in the Squalus maximus , (§. 472.)
there is an expansion of the Duodenum immediately below
the Stomach, the diameter of the rest of the intestine being
uniform throughout. In the Walrus, also, as in many
Fishes, the large intestine and coecum are but little deve-
loped, though somewhat more so in the Seal.

§. 522. In the hoofed animals, among which the Pachy-
dermata, by their unwieldy form, abundance of fat, &c.
form evidently an intermediate gradation between the
Cetacea and the higher species, the intestinal canal is ordi-
narily of considerable length. In the Elephant, according
to Home, the small Intestine measures 38 feet, the Colon
and Rectum, 2(H feet, and the Coecum H ; at the same
time, the canal generally, but more particularly the

* It almost appears as tliougli these animals hear tbc same lelation in this
respect to Fishes as the Aplysiaeund Cephalopoda to Zoophytes.

1 03

Ccecum and Colon, are very capacious. In the Hog the
Intestine is about thirteen times the length of the body :
the Colon, which, like that of Man, has two longitudinal
sets of fibres puckering it into a series of cells, is of consi-
derable length, and forms several spiral convolutions on
the left side of the abdomen. In the Ruminants the high
developement of the assimilative organs is indicated by the
•extraordinary length of the intestinal canal, not less than
by the organization of the stomach. In the Camel, for
instance, the length of the small Intestine is 71 feet, of the
Colon and Rectum 56 feet, of the Ccecum 3; the Coecum
and commencement of the Colon being very capacious, then
becoming narrower, and forming spiral convolutions. In
the Ram, according to Cuvier, the Intestine is 28 times
the length of the body: consequently the proportion is
the same as in the Seal. In the Solipeda the length of
the intestinal canal is somewhat reduced: according to
Home the small Intestine of the Horse measures 56 feet,
the Colon and Rectum 21 feet, and the Ccecum 2^; the
proportion of the whole to the body being about 10 to 1.
In the Zebra the small Intestine is 36^ feet, the Colon and
Rectum 19£, the Coecum 2\: the large Intestine, how-
ever, is usually of extraordinary width. The Anus in this
series of animals invariably forms a distinct orifice behind
the sexual and urinary passages : the Vermiform Appendix
appears to be wanting in all the species, except, according
to Daubenton,* in the foetus of the Manati (Trichechus
Manatus ), where it is even double, unless indeed one of the
two processes be the Ccecum itself.f

* Buffon, Hist. Nat. t. xiii. pi. $8, fig. 3, l.

f The relative proportion of the diameter of the intestinal canal to its
length has been already alluded to. In the Gibbon the length of the small
Intestine is to its circumference as 31 to 1 ; of the CcBcmn as 1 to 4- ; of the
Rectum and Colon as 3 to I. In the Maki Mococo, the length of thtj small

104

§. 523. Another series of Mammalia is formed rather
on the type of Amphibia and Birds. The Ornithorhynchi,
Ant-Eaters, Armadilloes, Sloths, as well as Bats, Rodentia,
Shrews, Opossums, &e. have already been noticed as form-
ing- intermediate gradations between them and the superior
species of Mammalia; and as the comparatively simple
organization of the Stomach already presented approxima-
tions to those Classes, so also does it happen with the in-
testinal canal. Consequently, we find it, as in those Classes,
of inconsiderable length, not more than about 3 to 6 times
as long as the body : a statement, however, to which there
is an exception in several Rodentia, e. g. Squirrels, Hares,
Beavers, and Kanguroos, where the proportion is as much
as 8, 12, or even 16 to 1, their relation to the Ruminants*
connecting them with the preceding series. In other in-
stances we find individual portions of the intestinal canal
distinguished by peculiarities of structure. First, in the
Ornithorhynchus and Echidna it is remarkable, that (as in
many Birds, §. 492.) there exists a Vermiform Appendix,
which differs from a common Coecum in not containing;

Intestine is to the circumference as 41 to 1 ; of the very long Ccecum as 2 to 1 ;
and of the Rectum and Colon as 1 to 1. In the Vespertilio noctula, where
the canal is shorter than in any other of the Mammalia, its length is to its
circumference as 28 to 1 ; in the Brown Bear as 37 to 1 ; the Hedgehog,
58 to 1 ; the Mole, 82 to 1 ; the Aquatic Shrew only 19 to 1. In the Otter
the proportion is 64 to 1 ; in the Martin, 66 to 1 ; in the Weasel, where
the canal is short in proportion to the body, only 25 to 1. In the small
Intestine of the Lion the proportion is 80 to 1 ; in the Ccecum, 5 to 6 ; in
the Colon and Rectum 7 to 1. In the Hyiena, where the canal is much
longer than in the other carnivorous Digitigrada, the proportion in the small
Intestine is 1 10 to 1 ; in the Ccecum 4 to 9; in the Colon and Rectum as
6 to 1. In the Squirrel, the ratio in the small Intestine is as 123 to 1 ; in
the large 20 to 1 : in the Ccecum of the Polatouclie as 1 to 1 ; the small
Intestine, as 50 to 1 ; in the Colon and llectum, as 12 to I. (Cuvier,
Comp. Anal. iii. 461 .)— Translator.

* The Kangaroo possesses even the power of Rumination. (§. 51 k)

105

fcecal matter, appearing1 to be rather a secretory organ : we
have to notice also the moderate length of the Intestine,
the small Intestine in an Ornithorhynchus 17i inches long
measuring 4 feet 4 inches, — the Colon and Rectum 1 foot
4 inches ; also the great uniformity in the structure of the
small and large Intestine ; and lastly, the common termina-
tion of the Rectum, urinary and sexual organs in a Cloaca
precisely as in Birds and Amphibia. In the Two-toed
Ant-Eater, also, as in many Birds, there are two small
Vermiform Appendices (Tab. XIX. fig. XX. m. n.): nay,
in the Daman (Hyrax capensis ), which has recently,* with
great propriety, been classed with the Sloths, there are two
long Vermiform Appendices, besides a large stomach-
shaped Ccecumf placed above them. The Wombat and
Kaola, also, according to Home, have a single Vermiform
Appendage, like the Ornithorhynchus.

§. 524. In many species, likewise, e. g. Armadilloes,
Pangolins, Sloths, Bats, Shrews, in the Hedge-hog, Badger,
Bear, Martin, Weasel, and in some Rodentia, as the Dor-
mouse and Rell-mouse, we find, in perfect accordance with
the type of the Amphibia (§. 481.), the small and large
Intestine scarcely at all separate ; at least not by a Coecum,
which is altogether wanting, but merely by an annular valve,
and usually remarkably short, — in the Mouse, Aquatic
Slp-ew, and Weasel, for instance, being 3 times, in the
H(?dge-hog 6 times, and in the Mole 7 times as long as
the body. It is only in those species more closely related

• Oken’s Zoologie, b. ii. s. 1087.

f This fact will serve to prove that the Vermiform Appendix cannot be
the point of connection with the Vesicula Umbilicalis; and also, that as Ver-
miform Appendices are here found considerably below the Coecum, which is
the extremity of the large Intestine, they do not consist merely in prolon-
gations of the large beyond the small Intestine, but are in fact repetitions of
the intestinal appendages found in Birds.

106

to the former series, e. g. in the Rodentia belonging to

. c5 O

this one, in the herbivorous Vampyre (lloussette), and in
the larger animals, such as the Bear, that the relative pro-
portion is increased, e. g. in the Vampyre, 9^ to 1 ; in the
White Bear, 10 to 1. It is remarkable, that almost all the
hybernating animals belong to this series, particularly when
we consider how completely hybernation is peculiar to the
Amphibia.

§. 525. These forms are connected in various ways,
partly with the Carnivora, and partly with the remaining
Rodentia. In the former, the Intestine is usually short,
(about 3 or 4 times as long as the body) ; the small and
large Intestine more uniform in their structure; the Caecum
for the most part extremely small (Tab. XIX. fig. XXI.
b.); though in Dogs, as in Marsupial Animals, it is longer
and convoluted on itself. On the contrary, in most
Rodentia, e.g. Hares, Beavers, Rats, Kanguroos, Squirrels,
Hamsters, Marmots, as already (§. 523.) remarked, the
intestinal canal is longer, the large Intestine and Ccecum
more considerably developed, after the manner of the
Ruminants, and, at the same time, frequently furnished
internally with numerous glands. The size of the Ccecum
is most striking in the Beaver, where it measures almost
two feet; in the Rat, (Tab. XX. fig. VI. c.) also, and in
the Hamster (Tab. XIX. fig. XVII.) its size is equal to
that of the Stomach. Its apex is not infrequently ( e . g. in
the Beaver and Plare) beset with many glands, does not
(contain any foeces, and resembles the glandular appendices
to the Stomach, which are likewise frequently found here.
The little ccecal pouch near the valve of the Colon in the
Hare, noticed even by Wepfeii, appears to me, from its
glandular and cellular internal structure, to correspond
completely to the Vermiform Appendix, notwithstanding
a slight variation in its form. Lastly, the intestinal canal

i or

of Apes, like- that of Man, is pretty nearly intermediate
between those of the Ruminants and Carnivora. The
considerable length of the Coecum in the Makis is worthy
of notice, and likewise the appearance of the Vermiform
Appendix to the Coecum in the Orangs.*

§. 526. On the termination of the intestinal canal in the
Anus, I have to remark, that in all Mammalia it is placed
behind, and not, as in Fishes, in front of the sexual and
urinary passages. The cloacal structure of the Ornithor-
liynchi has been before alluded to; but even in the Beaver,
the same common termination of the Rectum, urinary, and
sexual passages exists : nay, even the sac-shaped dilatations
found at the termination of the Rectum in several Carni-
vora, e. g. according to Daubenton, in the Hyaena,
(Tab. XIX. fig. XVI. a.) and in the Genett-cat, appear
to be a repetition of this cloacal expansion ; though in
those instances the urinary and sexual passages no longer
open into it. In very many Mammalia we again find these

* In the Vespertilio auritus, the villi of the Intestine are very nume-
rous, and generally pointed, but occasionally tuberculated or club-shaped.
In the Cat they are very long, arid terminate in acutely pointed processes.
In Swine, they are very numerous, and more or less ramified or subdivided :
in the large Intestine, instead of villi there are little eminences, which give
nearly a reticulated appearance to the surface of the membrane. In the Ox,
the^membrane is disposed in little folds in all directions; and is perfectly
villous throughout, the villi being very long and apparently pointed. In the
Mole, the inner membrane is raised into a great number of superficial trans-
verse folds intersecting each other, so as to form a net-work with interstices
of various sizes : as they approach the anus, the folds become smaller, so that^
the membrane presents merely the appearance of little points. It deserves
to be mentioned, that in the various animals of different classes which
Rudolphi examined for the purpose, he was unable to discover in the healthy
state the orifices of the supposed Lieberkuhnian ampullae. (Reil’s Archiv.
iv. 63.) In the Rhinoceros, the inner surface of the Intestine is remarkable
by being raised into pyramidal tufts or processes, which serve the purpose of
Valvulac cqnuivcntes. (Thomas in Phil. Tram, 1801, p. 150.) — Translator .

108

last mentioned dilatations, as well as tlie orifice of the
anus itself, surrounded by glandular pouches and secretory
organs, similar to those existing in the three preceding
Classes. These anal glands are peculiarly developed
around those dilatations in the Hygena (Tab. XIX. fig.
XVI. e. g.), and also present themselves as tolerably large
pouches on each side of the anus, and secreting an oily
odoriferous substance, in the Lion, the Cat, and several
Rodentia. In the Badger there are several similar, but
smaller, glands, opening into a peculiar sac above the
Rectum: in the Civet and Skunk,* on the contrary, this
sac is placed between the anus and the opening of the
sexual organs. Of the same kind, also, are the glandular
bags of the Beaver, which secrete Castor, and open into
the Cloaca: and we shall hereafter find repetitions of these
in perfectly similar secretions from the sexual organs, &c.

§. 527. In Mammalia, as in the preceding Classes, the
attachment of the convolutions of the Intestine is effected
by the reflection of the folds of Peritoneum surrounding
the canal, i. e. by a Mesentery. It is remarkable, how-
ever, that here, and even in Man himself, we find elonga-
tions of those folds, Omenta, in which there are frequently
collections of fat resembling those in the abdomen of
Insects. This is particularly the case with the great
Omentum of the hybernating animals of this Class, in
which the accumulation of fat is very great before the com-
mencement of their torpidity, resembling the fatty mass in
the Caterpillar before its metamorphosis or sleep as a Pupa.
According to Cuvier, in addition to the usual large Omen-
tum, some hybernating animals, as the Marmot, Dormouse,
and Jerboa, have likewise two lateral appendages, pro-

* It is remarkable how, in this animal, a secretion at the anus forms a
njeans of defence (by its odour), like the black fluid of the Sepia, or the
poison of the Scorpion and Bee, though in a different manner.

1 09

ceeding from the lumbar region, and devoted to tin? same
purpose.

§. 528. Before quitting the consideration of the organs
employed in the introduction of nutritive materials, it yet
remains to solve the question, — how far the human organi-
zation in this respect precedes that of other animals?
From what has been already stated, it is evident that this
precedence can consist neither in the powers of the teeth
with which the jaws are provided, nor in the force of the
muscles belonging to the jaws, nor in the greater compli-
cation of the structure of the stomach, nor in the length
and capacity of the Intestine ; all of which would have been
incompatible with the more elevated character of the human
nature. Consequently, the peculiarities of this organiza-
tion not residing either in the force of its assimilative or
muscular power, the higher developement of nervous
activity, which constitutes the general characteristic of Man,
will be found to form, in this instance also, the sole ground
of pre-eminence. That superior developement is most
decidedly pronounced at the cephalic extremity of the
intestinal canal, where it presents itself as a peculiar der-
moid sense, that of Taste ; and it is easy to demonstrate
that in no other animal is a similar developement of that
sense favoured in the same degree, by the delicacy of the
organ, as in Man.* The other circumstance, which might
be considered as characteristic of Man in this respect, viz.

• Physiologically it is not unimportant to remark how completely this
higher developement of the sense of Taste in Man corresponds to the more
elevated condition of the sense of Touch (§. 34-4.), which, as a branch of
the general cutaneous sense (§. 92. 95.), is parallel to it ; and also, that it
is the two divisions of the general intestinal sense, t. e. Taste, and the sexual
sense, which admit of being elevated to the more animal feeling of voluptu-
ousness. They are the two senses which possess the lowest rank ; and have
the same relation to Touch and Smell, as Digestion and Generation have
to Respiration and Motion.

the structure of the organs just considered, by which they
are adapted to the greatest possible diversity of food, is,
however, much less strictly peculiar. Among the particula-
rities of organization belonging to this head, I may mention,
however, 1st. The position and form of the teeth, which,
being intermediate between those of herbivorous and carni-
vorous animals, are chiefly characterized by forming an
uninterrupted range, a circumstance in which Man is
equalled, according to Cuvier, by a single species of ani-
mals only, and that one fossil and provided with much
longer jaws (the Anoplotherium). 2d. The proportions of
the (Esophagus, Stomach, and Intestinal Canal, already
incidentally noticed, presenting themselves as intermediate
between those of other Mammalia, the greater simplicity
of the Stomach being compensated by the increased deve-
lopement of the Colon, as well as Ccecum, with its Vermi-
form Appendix. We find, too, a remarkable proof of the
accuracy of the principle of a gradually progressive deve-
lopement of organization, in the fact, that the new-born
Child, as regards the mode of ingestion of nutritive matter,
re-approximates to the inferior Classes of Animals, and
wanting teeth receives its nutriment by Suction, like a
Polype or a Worm.

Chap. III. Of the Organs of Respiration and Secretion.

§. 529. As the animal is related to the Earth by the
necessity for Nutrition, so likewise is it to the Atmosphere
by the need for Respiration. Both are equally important
conditions to the manifestation of life, inasmuch as both
contribute, though in different ways, to maintain the con--
stant change of composition of the bodily frame. It is
true that in Digestion, as in Respiration, external materials
are taken in, and internal thrown off; but quite in inverse
proportion : because, in Respiration rejection and volatili-
zation as much predominate, as do intro-susception and
approximation in Digestion. Hence, however simple the
animal may be, the unceasing change in the composition
of the organic mass must still exist, together with the con-
trast between ingestion and excretion. But as Respiration
must be considered as the first and fundamental Secretion,
founded on the relation of the animal to the medium in
yhich it exists, and produced by the previous access of an
atmospheric element (Oxygen), the remaining Secretions
in the body appear as repetitions of this primary one, and
the secretory as Metamorphoses of the respiratory organs, —
an idea of which the comparative review of animal forma-
tions will afford, and in fact has already (§. 455.) afforded*
evident examples.

§. 530. W e shall proceed to consider the organs devoted
to this purpose in the following order : first of all, we sliall

describe the cutaneous excreting surface, with its various
transformations, in the animal series, as fundamentally
opposed to the internal absorbent intestinal surface ; not
treating, until afterwards, of the processes developed from
the former, sometimes internally, sometimes externally, and
which, presenting themselves either as pulmonary cavities,
or as laminated Gills resembling the form of the leaf,
(which in Plants constitutes the chief organ of Respiration,)
perform with greater energy the same functions as the
Skirt, and form true respiratory organs. We shall then
still have to examine the repetitions of these organs in the
remaining Systems, the Organs of Secretion, which are as
follows : First, the repetition of the respiratory Organs in
the Intestinal System, to which belong the Organs of Se-
cretion connected with the Intestinal Canal, and of the
utmost importance to Digestion, — the Salivary Glands,
Liver, &c. ; and secondly, the repetition of the respiratory
Organs in the Sexual System,* with which must also be
classed the Urinary Organs.

I. Of the different For.ws of the Cutaneous Organ.

Section I. In 'Zoophytes.

§. 531. As we already remarked that in these animals
the Intestinal Canal was not yet distinguished from the
rest of the animal substance by peculiar parietes, but rather

* Even the sexual function itself consists properly and essentially in ex-
cretion, a fact wh eh may materially assist in explaining the connection so
commonly remarked between generation, respiration, and the nourishment
of young.

113

excavated, as it were, out of the general mass of the body ;
so also, in the inferior Orders of this Class, e. g. in Polypes,
we find that the body is not covered externally by any
distinct membrane, but merely by a superficial mucous
coating-. Already in the Medusae, on the contrary, and
even in Species where the internal substance is altogether
homogeneous, there is an investing membrane, interspersed
with little granules, and easily removed in detached por-
tions.* It is peculiarly remarkable, on this account, that
the gelatinous fluid which it pours out (perhaps a solution
of the substance of the body itself) is, according to Spal-
lanzani’s observations,! probably the actual substratum^ of
the phosphorescent lights which has been remarked by so
many Naturalists in these gelatinous bodies (Medusa,
Beroe), and which occasionally illuminates the whole sur-
face of the ocean.

§. 532. Though, in the Species above-mentioned, the
surface of the body appears merely as a mucous coating, or
mucous membrane, which is in many respects analogous to
the Epidermis of Plants, |] in others, on the contrary, e. g.
in Madrepores, Tubularise, &c. we find other materials
secreted from the external surface, whence originate the
horny and calcareous envelopes before spoken of. (§. 62.)
In the larger Zoophytes, also, e. g. in the Echini, there is

1 ' Giide, Beytrag. zur Anat. und Physiol, der Medasen. s. 12.

f He found that water, milk, &c. were rendered luminous by being mixed
with this secreted mucus. (See Macartney upon Luminous Animals in
the Philos. Trans. 1810. p. 287.)

1 I say substratum of the light, because the exciting cause is derived
partly from without, and partly from the sensible qualities inherent in animal
matter. This Phosphorescence, as well as the power of Stinging, before
(§. 00.) mentioned, give rise to many interesting comparisons.

|| Orundzi'ujc der Anatomic dcr Pjlanzen, von Kieser, fan. 1815. s. 131.

VOL. II. I

114

a similar secretion of earthy matter, though, as it appears
to me, it is no longer completely external, but, nearly as
we shall find it in the superior Testacea, deposited in the
form of an ossified rete mucosum between the membrane
surrounding the Intestines, (Peritoneum,) and external
shin. In the Asterias, the fibrous case of the body has been
already noticed (§. 66.) as an organ of motion; but even
this is covered externally by a kind of epidermis, and, con-
sequently, its fibrous, and in part calcareous, shell, is in the
same manner to be considered only as an ossified rete
mucosum, capable of motion by means of cutaneous muscles.
Physiologically, not only the composition, but likewise the
colour, of the outer surface of the body is important; on
which point I may remark that, though the inferior Zoo-
phytes, (Infusoria, many Polypes, &c.) the embryos of the
animal kingdom, appear altogether colourless and transpa-
rent or white, yet, that in others the body itself, or the
shell, present evident and frequently very beautiful colours:
thus the Hydra viridis is green, the H. vulgaris yellow ;
whilst JEquorea, Beroe, and' Holothur-ia, often present ex-
tremely beautiful blue, red, or green colours: of the inter-
nal or external shells of Zoophytes, I will mention only
red Coral, and the different colours of the Edhini and
Asterias.*

* In Star-fish, e. g. Asterias anrantiaca , the external covering is formed
in each ray by a considerable number of bone-like masses, decreasing gra-
dually in size from the base to the point of the ray, connected together in
such a manner as permits of motion one upon another* and forming collec-
tively a groove or channel, in which the parts contained within the ray are
lodged, and which is formed into a perfect canal by a hard firm membrane
attached' to the edges of the masses- in each ray. The number of pieces in
each segment of a ray is eight, and the number of segments in each ray about
eighty, making altogether from 640 to 700 detached pieces in each, and from
3200 to 3500 in the whole body. (Meckel VergL Anatomic, th. ii. abth. i.
25.) — Translator

115

Section II. In Mollusca.

§. 533. Here, also, the skin appears for the mo9t part
as a mucous membrane, coinciding very closely with the
internal mucous membrane of the Intestinal Canal, and
but imperfectly distinguished from the subjacent body :
amongst the Acephala, however, the Ascidise form a re-
markable exception, for in them the gelatinous or leather-
like case of the body (§. 122.), which in itself is probably
insensible, is frequently connected only by cellular
tissue, and occasionally only at the apertures of the mouth
and anus, with the muscular bag inclosing the viscera, and
of which it appears to be a product. (Tab. II. fig. I. a.)
Besides, the external covering of these animals is usually
very slimy ; nay, in the Pinnae, Mytili, &c. there is, as has
been already remarked, (§. 128.) a peculiar complicated
gland on the under surface of the Foot, secreting a tena-
cious fluid, which, when drawn into threads, affords the
means by which the animal attaches itself to rocks, &c.

The skin itself in these species is delicate, and frequently
possesses considerable elasticity, inasmuch as we find that
the Foot, an organ which is capable of considerable elon-
gation, does not present any very large wrinkles when con-
tracting. Here, too, shells appear to be formed over the
membranous cloak, first by the coagulation into a thin
cuticle of the mucous rete secreted from the external sur-
face of the cloak, which is subsequently indurated from
within into a thin stratum of Carbonate of Lime, to which
new layers are gradually added from within, the last depo-

i 2

sited differing from those which are more external in con-
taining a greater quantity of animal jelly, and, consequently,
presenting the nacreous lustre.*

§. 534. In these respects its organization is the same
as that of the skin in the Gasteropoda and Cephalopoda,
in which the external surface of the body, when not covered
by shells, is found soft and slimy : it is, however, by no
means to be considered as a peculiarly delicate organ of
touch, inasmuch as the proper seat of cutaneous feeling,
the Corpus papillare, rich in nerves, is wanting, the mucous
rete and Cuticle being still closely attached to the muscular
cloak. (§. 133.) The cuticle appears less elastic than on
the Foot of Bivalves, whence the surface is wrinkled when
the body is contracted. As to the formation of shell, it is
usually effected here, as in the preceding Order, between
the cuticle and a mucousf surface, which in Snails with
shells (somewhat as in the Echini, §. 532.) is either the
Peritoneum itself, which incloses the viscera that are ex-
ternal to the body, (§. 130.) or the edge of the Cloak :
there are species, however, in which the shell is covered
not merely by the cuticle, but also by a stratum of muscular
fibres, e. g. in the Sepise, Aplysiae, and Slugs. (§. 129.
133.)' The fact remarked by Swammerdam, J of the em-
bryo of the viviparous Snail, viz. that the cuticle covering
the external surface of the shell is beset with many little
bristly hairs (Tab. III. fig. XII.) is remarkable, inasmuch

* This deposition of layers is perfectly analogous to the annual deposition
of rings of new matter in many plants.

| It has been recently remarked by Nasse (Meckel’s Archiv. b. ii. h. +),
that this mucus, as it is called, is rather an albuminous matter. It is evident
that more accurate chemical examinations of such cutaneous secretions,
compared with similar analyses of the substance of the body, may be expected
to afford many interesting results.

\ Bill. Nat. p. 75.

117

as a similar hairy superstratum is found on the Shell in
many Acephala, e. g. in the Area pilosa.

§. 535. The colour of the surface of the body is very
various in this Class, but frequently very vivid, and more
commonly so in the marine than in the fresh-water species.*
In the Acephala, the Shells are usually more coloured
than the body concealed within them; though occasionally
the latter gives out a phosphorescent light, f whilst the Foot
which is protruded from the shell frequently alone presents
more determinate colours, e. g. yellow or red. Such, also,
is the case with the Shell-Snails, whilst, on the contrary,
Slugs occasionally present more vivid colours, yellowish-red,
brown, grey, spotted, &c. The Cephalopoda are but faintly
coloured, — reddish, violet, &c. Invariably, however, the
seat of colour is in the rete mucosum, or shell produced
from it, the external skin being colourless. The symme-
trical markings of Snail-Shells may be explained by the
gradual increase of the shell, in accordance with the cor-
responding increase of the subjacent secreting cutaneous
surface, variously organized in different parts.

j Section III. In the Articulata.%

§. 536. In the inferior Orders of this Class, the principal
circumstances of the skin are essentially the same as in the

* Von Goethe zur Farbenlehre. b. i. s. 236 It is remarkable, also,

that phosphorescence is most common in marine animals.

f In the Pholades for instance.

$ We shall treat more fully hereafter on the change of Skin, which- fre-
quently takes place in this and some of the succeeding Classes.

118

uncovered Mollusca. Such is the case in the colourless
Intestinal Worms, in which the cutaneous differs so little
from the intestinal surface, that the skin itself forms an
extremely active organ of absorption. (§. 443.) The
organization of the skin is similar in the Earth and in
Aquatic Worms, as well as in many Larvae of the higher
Insects, particularly Maggots. In the Crustacea, the skin
resembles that of the Testacea. But even in Worms the
external skin is more distinct from the body : it separates
very readily, in the Dew-worm for instance, and then more
nearly resembles the human epidermis ; nay, beneath this
superficial skin is another which is more closely connected
with the fibrous stratum, but, nevertheless, forms a new
epidermis when the external one is detached. The case is
similar with the skin of the Larvae of Insects, and even
with the Crustacea: here, as in the testaceous Mollusca,
the external skin formed by the solidification of gelatine is
combined with the ossified, or rather petrified, rete muco-
sum, so as to form an earthy Shell : with this difference,
however, that though in both instances the shell once formed
is no longer nourished by vessels, (an invariable point of
distinction between bone and shell,) no new layers are here
deposited internally, as on the shells of Bivalves, but that
the succeeding newly-formed stratum forms both skin and
shell after the old one has been thrown off, nearly in the
same manner that a permanent displaces a milk tooth.

§. 537. One kind of productions from the surface of the
skin which arrives at a high degree of developement in the
Articulata is peculiarly remarkable, but first presents itself
in the vegetable kingdom, viz. Hair. In Plants where the
external surface is chiefly devoted to respiration, the Hairs
appear partly subservient to this purpose, and partly agents
in various secretions.* In animals we find these organs
* Kieser, Anatomic der PJJanz. s. 160.

119

present themselves when the external skin begins to be
more definitely developed as a peculiar structure, and when
at the same time respiration becomes more absolutely dis-
tinct. This is already noticeable in the Mollusca, (§. 534.)
but still more in Worms: to this head belong the small
bristles of the Dew- Worm, (§. 139.) serving partly as
organs of motion ; the larger ones, both soft and bristly,
of the Nereides, &c. ; and particularly the glittering ones
of the Aphrodita. Even in the Crustacea, notwithstanding
the petrified surface of the skin, the hairs do not altogether
■disappear ; as we find them very evident on the edges of
the scuta ; on the legs, where they appear to protrude
from the pores of the shell ; and, above all, on the outer-
most pair of Maxillae in the Cray-Fish ; and usually dis-
posed in tufts, f as in those of Worms. They are found
likewise in very many Larvae of Insects ; in which, as soon
as the outer skin varies from the state of the gelatinous
surface of the Mollusca, and becomes more horny, we
find these productions presenting themselves in greater
number and perfection. Thus, for instance, in the Larvae
of Gnats, of the Myrmeleon, and CEstrus, there are only a
few faintly coloured bristles disposed in tufts ; in Cater-
pillars, on the contrary, there are hairs of various colours,
either very long, or subdivided, and of different degrees
of firmness. In microscopical examinations of single hairs
of Caterpillars, as well as of Cray- Fish’s bristles, I have
always found them forming an uninterrupted canal, nearly
as the hairs of Man.*

f \\ e niay in some respects consider hairs as Zoophytes placed upon other
animals, the bundle-like manner in which they almost invariably at first
appear, corresponding to the manner in which Polypes are disposed in bun-
dles or tufts.

. * In the Aphrodite aculeata the bristles are arranged along the whole of
the lateral surfaces of the body in about 35 transverse rows. They decrease

120

§. 538. Lastly, in perfect Insects we again find the
cutaneous coverings in the inferior species receding nearer
to Vermes and Crustacea ; in others, on the contrary, par-
ticularly as regards the structures produced from them,
advancing to an extraordinary degree of developement.
Of the former kind are the Gnathaptera and Aptera ;
where the skin is formed in layers nearly as in the Larvae
of Insects, the inferior layer throwing off the upper, and
each layer being essentially similar to the other. The ten-,
dency to induration of the cutaneous organ is still, how-
ever, occasionally evident, as is proved by the shells of the
Scorpion ; in others, on the contrary, inconsiderable, e. g.
in Spiders, where the thin cuticle allows the colour of the
subjacent rete mucosum to shine through. The Hemip-
tera, Coleoptera, Diptera, Hymenoptera, and Neuroptera,
also present, at least on the body and legs, the same horny
condition of the skin, though usually of more brilliant
colours, and frequently decorated with a true metallic
lustre. The skin on the wings is here extraordinarily
delicate, and very similar to the human epidermis ; with
the exception, however, of the Coleoptera, where the upper

in number, size, and hardness, as they proceed from the middle of the body,
either forwards or backwards, the posterior in particular being very inconsi-
derable. The inferior differ from the upper in being situated upon the point
of a projecting copical tubercle, which is itself subdivided into three papillae:
each of these papillae hgs hiistles attached to it, which are thus arranged in
three rows, viz. from 4 to 5 in the lower, and 2 in each of the upper papilla.
The superior bristles are placed in a row, and not upon tubercles, being
larger and stronger than the lower ones, and the number in the middle rows
about 14. On an average of 16 bristles of both kinds in each of the 35 rows
or bundles, the total number on each side will amount to nearly 600. At the
lower part of the row of superior bristles are numerous long but weak hairs,
with a glittering metallic lustre, together with a felt-like texture, which
steadies those bristles, and extends over the whole of the back of the animal,
but not to the tubercles upon which the inferior range of bristles is fixed.
( Meckel, Very l . Anatomic , til. ii. abtli. i* 46.) — Translator.

121

wings (elytra) present themselves as moveable horny la-
minae, (opercula, §. 150.) In each ot these Sub-Orders
likewise there are hairs ; which, either separated, though in
great numbers, cover the whole of the tender body, as in
many Spiders, Flies, Humble-Bees, (in which those ot the
back are feathered,) and Gnats; or again project in tufts
from the firm crusts, as in many Coleoptera. Lastly, in the
Lepidoptera, the cutaneous organ is developed into the
most brilliant glittering colours, as well as most numerous
and delicate productions: not only is the rete mucosum,
which in the Articulata continues to form the first basis of
the skin, consolidated into a softer kind of horny crust,
(which again may be viewed as a dense intertexture of
single hairs,) but also there appear on its upper surface
either single satin-like hairs, or ramified hairs (feathers), or
little horny scales fixed to stalks, and representing various
forms of the leaves of Plants, (Tab. VII. fig. XXV.) cover-
ing the delicate membranes of the wings, and forming the
coloured powder which constitutes the most ornamental
variety in the markings of these (almost flower-like) animals.

§. 539. If, before passing to the higher animals, we
take a retrospect of the order of succession in the develope-
ment of the cutaneous organ, we find in the Zoophyte the
mucus secreted from the external surface of the body first
consolidated into a coarse earthy mass, or a mere cuticle; in
thd Mollusca the skin altogether corresponding to a mucous
membrane, and the earthy shells, when they exist, covered
by a distinct cuticle ; the animal in this, as in the pre-
ceding Class, but little coloured, and thence more fitted
in general for radiating phosphorescent light. In the Arti-
culata, lastly, where even the name indicates the greater
developement of the external form, Vermes and Crustacea
offer repetitions of the Mollusca, whilst in Insects we meet
with the highest point of perfection of the colour and

structure of the skin in the first division of the animal
kingdom.* The skin itself here imitates the hairs, tie
respiratory organs of Plants, nay even (in its coloured
scales) the leaves in the most perfect manner ; and when
the hairs by their ramification appear as feathers, for in-
stance, on the wings kof Moths and the bodies of Bees,
it must be considered as a repetition of a form of the res-
piratory organs to be hereafter described — Gills.

§. 540. Lastly, we have to remark that the Articulata
also have the power of producing a phosphorescent light,
which, according to Macartney,! is probably produced in
this as well as the preceding Classes by peculiar secretions.
Phosphorescent species are most common in the Genera
Cancer, Limulus, and Lynceus, among Crustacea ; Nereis,
among Vermes ; and among Insects, in Scolopendra, Lam-
pyris, Elater, Fulgora, and Paussus. In phosphorescent
Insects the light is produced, according to Macartney,
from a yellowish matter secreted by peculiar bladder-like
organs, (Tab. VII. fig. XVIII.) and placed behind a trans-
parent spot of the horny covering, without any appearance,
however, of a peculiar nervous or tracheal apparatus. The
situation of the light is by no means the same in all cases;
a fact which makes it improbable that it has any fixed rela-
tion to other organs,* e. g. to the Nervous System : thus

* It is remarkable to observe that in this as well as in the next series of
animals, the colouring of the dorsal is always more brilliant and distinct
than that of the abdominal surface, the one being exposed to the light, the
other to the ground. In this respect, as well as in the brighter colours of
the animals of warm climates, we again clearly find that light serves not only
to display, but also to produce colours.

f Phil. Transact. 1810. On Luminous Animals.

J Treviranus, in his Vermischte Schrift.cn, b. i. 1816, has imputed seve-
ral errors to the observations of Macartney, and conceives that he has
detected the little phosphorescent sacs on the abdomen to be air-bags ; and

123

the Glow-Worm shines oil the middle rings of the abdomen,
the Lantern-Fly (Fulgora lateruaria) on the hollow pro-
jection from the head, and the Elater noctilucus on the
Thorax. In the higher Classes we find this phosphores-
cence of the surface of the body probably in only a few
Fishes, though even here there may be some delusion,
Fishes being considered as phosphorescent merely from
being covered by small phosphorescent Zoophytes.

Section IV. Of the Skin in Fishes.

§. 541 . In most species of this Class the structure of
the skin is more complicated than in the preceding. In
immediate contact with the muscles, and closely adhering
to them, we find a kind of corium, so thin that it can usually
be raised in but small pieces. From it arise the scales,
surrounded by rete mucosum, and overlapping each other
like tiles : they consist of horny or bony laminse, which we
may consider as little shells of Bivalves or Snails, partly
because they are produced from the same situation, and
partly because, like them, they increase by the deposition
of new layers and circles. Here, too, pretty nearly as in
the more perfect Zoophytes, (§. 532.) the rete mucosum is
the seat of the colours, which are frequently very vivid.

farther, that the genital organs are the true source of the light. Still, accord-
ing to this opinion, it is scarcely intelligible how the light should appear at
other points, e. g. the Head and Thorax. As I have not hitherto had any
opportunities of fully examining these points for myself, I did not feel myself
.justified in giving an exclusive preference to the views of either of these writers.

124.

Lastly, the .external stratum of the skin is formed by a
thin cuticle, formed by the superficial consolidation of the
rete mucosum, and constantly lubricated, as in the Mollusca,
by an albuminous slime.*

§. 542. The structure of the scales in this Class pre-
sents many varieties.f In the vermiform Fishes, e. g. Eels,
they are extremely small, and scarcely visible, the skin, as in
many Vermes and Mollusca, being little else than a mucous
membrane : sometimes they are placed one over another as
semilunar horny laminse, rarely of a very large size, the
uncovered portion alone of the scale displaying its colours
through the albuminous coating. We must not omit to
notice, with regard to those colours, that they are here
again darker on the dorsal than on the abdominal surface;
and that, even in the Pleuronectes, the lateral half of the
body which is exposed to the light is darker than the cor-
responding one averted from it. Not infrequently we find
the scales actually ossified, and provided with projecting
spines or points, — as in the Sturgeon, Stickleback, Diodon,
and Spinous Ray. In the Cartilaginous Fishes these indu-
rations of the rete mucosum gradually disappear altogether,
and at the same time with them the various glittering
colours qf the surface. In Lampreys we find only a tole-
rably dense cor iuiq, firmly attached to the muscles, and
covered externally by a granular cuticle. In the Electric
Ray the skin is softer, and less closely attached to the
muscles : in other Rays, on the contrary, and also in most
Sharks, rough, and furnished with coarse granules ; on
which account they are commonly employed in polishing,

* The blue colour of Fishes when boiled, or digested in alcohol and acids,
depends on the coagulation of this Albumen.

f It is physiologically important that almost all the organs of the skin of

animals, — Hair, Feathers, Bristles, &c exist also in Hants. As to scales,

we find them evidently represented by those of many roots.

The mucus which lubricates the surface of the body ini
Fishes is secreted by reddish glandular bodies usually
arranged along the lateral line, and poured out by pecu-
liar excretory ducts, which not infrequently perforate the
scales. In the Rays and Sharks these ducts are peculiarly
large; and in the Lampreys their apertures present
themselves as distinct points* particularly about the head.

Section V. Of the Skin in the Amphibia.

§. 543. In Frogs and Salamanders the structure of
the skin approaches to that noticed in several cartilaginous
Fishes, consisting in a tolerably dense though not very
strong corium, which is covered externally by a rete muco-
sum, ordinarily of no very brilliant colours ; and that again
by a very delicate mucous cuticle. It is remarkable in
Frogs, that the skin, almost like that of the Ascidise,
loosely surrounds the muscles, being attached merely by
vessels, nerves, and some cutaneous muscles ; of which the
latter only appear When the skin and the muscles of the
bo<jy are but little connected, and consequently are want-4
ing in the inferior animals, where the muscles themselves are
at one and the same time muscular membranes, and cuta-
neous muscles. The slimy, slippery skin, as in Fishes,
still appears as a mucous membrane, and has many glands
distributed throughout it. This is particularly evident in
the Salamander (Lacerta Salamandra ), which has a double
range of them along the spine, and two large ones at the
joint of the jaw perforated by many openings. By means

of tlie milky liquor secreted by them, the animal can querlcli
a small quantity of fire ; and hence the fable of its being
able to live there. According to some observations,* the
fluid appears to be poisonous. In the Toad the glands are
more diffused over the surface of the body. The results of
the excellent observations and experiments of TowNSON,f
as to the absorbing power of the skin in Salamanders,
Toads, and Frogs, are very remarkable, resembling in
every respect the absorption from the external surface
in the Intestinal Worms and Zoophytes. (§. 433, 443.) He
found that these animals have the power of absorbing the
fluids necessary for their support, and that in large quan-
tity, (as much as the weight of the body,) through the
external skin, or even through that of the abdomen alone; a
large part of them appearing to be retained in the so called
urinary bladder, though gradually thrown off again by the
skin ; except, indeed, \Vhen the animal suddenly ejects the
fluid from the bladder, which ejection, however, may serve
not so much as a means of defence, as of unloading the
animal for flight. |[

* Oken, Zoohgie, b. ii. s. 198. Pliny entertained the same idea, which,
however, is not confirmed by the experiments of Laukenti. ( Synopsis rep-
xilium, p. 195.)

f On the Absorption of the Amphibia, in Tracts and Observations in
■Natural History. London, 1799.

|| In the Toad the skin is furnished witli mucous follicles, which secrete
a thick yellow fluid, possessing poisonous qualities. They are most nume-
rous about the neck and shoulders, but are also pretty universally distributed
over the whole surface. The integuments are of peculiar firmness, owing to
the presence of a stratum of cutis immediately below the rete mucosuin ;
semi-transparent, yet so firm as not easily to be cut, and abounding in Phos-
phate and Carbonate of Lime with Carbonate of Magnesia. Dr. Davy, from
whom this description is derived, adds, that the secretion from the skin is
highly inflammable, and may perhaps be the production of a process auxili-

127

§. 544. The relations of the cutaneous covering* inf
Tortoises are generally the same as in the preceding Order:
as to the shell, we may remark that it is to be viewed in
the same light as the scales of Fishes or the shells of
Bivalves, inasmuch as, like them, it originates and receives
its colour from the rete mucosum, and is covered by a con-
tinuation of the cuticle covering the soft parts. It differs,
however, in this respect, that the scale-bearing skin rests
immediately upon the expanded and consolidated bones of
the thorax, although this immediate attachment of the skin
to the bones is often found in other parts, particularly the
head of Amphibia. The degree of hardness of the shells,
as well as their arrangement and marks, are very various ;
the colours rarely very vivid.

§. 545. Whilst Frogs and Tortoises in many respects*
and, among others, in the structure of the skin* approach
to the Mollusca and Cartilaginous Fishes, so, on the con-
trary, Serpents and Lizards approximate in that point rather
to the Osseous Fishes. In fact, the condition of the skin
and its scales is here actually the same as in most of those
Fishes : in the Crocodile they are gradually ossified nearly
as in the Sturgeon ; nay, the abdominal scuta of Serpents,
each corresponding to a dorsal vertebra and pair of ribs,
answer most completely to the mode of articulation of the
body in W orms ; with regard to which it deserves notice,
that7 this repetition of an inferior form presents itself only
on the under surface, the darker or parti-coloured dorsal

ary to the function of the Lungs. In conformity with this supposition it is
remarkable, that he found the’ Pulmonary Arteries each dividing into two'
branches, one of which proceeds to the Lungs, whilst the other, very little
smaller, is distributed on the cutis about the head and shoulder, and is ex-
tensively ramified where the venom follicles are situated ; in which part there
is also a plexus of veins of great size, as if intended as a reservoir of blood.
(Daw, Phil Trans . 1826. P. ii. 127.) — Translator,

surface being covered with separate scales. The skin of
these Amphibia differs from that of Fishes, partly in being
less firmly connected with the muscles, and partly because
the Cuticle is less slimy and more solid than in Frogs and
Tortoises; whence, as soon as a new stratum is formed by
the rete mucosum, the outer old one is thrown off in a single
piece, and that, without the scales, though their impression
is Very evident on the rejected slough. The claws of the
toes in Lizards may be noticed as new productions of the
skin in this Class, which, growing from the rete mucosum
in the form of strong scales, are fixed round the last bony
phalanges of the toes. The colours of the rete mucosum
in these animals again appear to attain peculiar brilliancy;
and probably, also, the organization of that stratum may
form the true cause of the well-known, though frequently
exaggerated, change of colour in the Chameleon, which*,
like blushing in Man, appears to be dependent on the tem-
porary fulness of its vessels. Lastly, the papillary struc-
ture, the proper seat of the cutaneous sense, of which
there were not any traces in the preceding Classes, appears
in this, and particularly on the soles of the feet in Frogs,
the Salamander, and Lizards, but more especially, accord-
ing to Cuvier, in the Chameleon, where the little papillae
present themselves in a nipple-like form. Cutaneous
glands, though not wanting, are but little developed in
Lizards and Serpents : in some of the latter they commu-
nicate a musky smell to the animal. Among the most
remarkable cutaneous secretions are, the highly viscid fluid
on the foliated toes of the Gecko; the musky secretion
produced by a gland on the lower jaw of the Crocodile;
and lastly, that from the chain of glands on the thighs of
several Lizards.

129

Section VI. Of the Skin in Birds.

§. 546. Birds are as much distinguished among vertebral
animals by the high degree of developement in the organi-
zation of the skin as Insects among invertebral. As to the
skin itself, it is circumstanced almost completely as in the
preceding Classes ; being even scaly on some parts, e. g.
the feet; or altogether naked, as in the neck of many
Vultures ; or attached to the bones, as on the bill. Here,
as in Amphibia, we can distinguish the three usual layers
of the skin, and even the papillary structure on the surface
of the feet, as in some Lizards, e. g. in climbing and swim-
ming Birds. The true skin, as in the preceding Classes,
is thin, and, together with the feathers inserted into it,
moved by cutaneous muscles, and connected to the sub-
jacent parts by a cellular structure, which differs from that
of the preceding Classes by its great tendency to the depo-
sition of fat. The rete mucosum is colourless in the parts
covered by feathers, and allows the blood to shine through
it ; whence the surface of the skin appears white, reddish,
and occasionally even somewhat grey. In the parts that are
exposed, the legs, combs, ceres, &c. its colour is very vari-
able,— yellow, red, blue, black, &c. as Natural History
indicates. The scales of the legs, the claws of the toes,
and occasionally also of the thumb on the wing, are not
essentially different from those of Lizards. The substance of
the projections occasionally found on the head, e. g. in the
Cassowary, is pretty similar to the covering of the Bill.

§. 547. The most remarkable point, however, in the orga-
nization of the skin in Birds is the production of Feathers

VOL. u.

] 30

In order to trace the transition from earlier structures to this*
we must refer to the ramification of Hairs in many Insects,*
but more particularly to their tuft-like projection in others,
and even in Worms. In the young Bird we first find that
tufts of soft hairs, instead of feathers, project from the
pores of the skin in a quincunx order : these hairs are,
as it were, only the summit of the true feather, whilst the
sheath or bulb from which they project forms its first cover-1
ing, and subsequently the hollow quill. In this sheath,
which is originally closed, the shaft of the feather is formed,
nearly like the leaf folded within a bud : this shaft may be
compared to- a strong hair, (it rarely happening that two
shafts arise from a single stem,) and, like the hair of
Plants,f consists inferiorly of cells, and terminates superiorly
in a solid point. Round this point is twisted a blackish ||
slimy tissue, which, when unfolded, dry and divided, forms
the vane of the feather. The quill, or sheath of the feather,
is connected with the skin by a fossa or umbilicus, almost
like the prickles of the Echinus, and contains pretty large
vessels for the cellular body of the shaft, which still remain
visible when the feather has attained a considerable size ;
at least, in a young Crow, in which the pinion-feathers
were five or six inches long, I could easily inject the whole
quill with quicksilver from the Brachial Artery.

§. 548. When the sheath of the feather (the quill )

* The hairs of Bees are perfect feathers, except that their vanes are widely
separated : the coloured scales of Butterflies are feathers with laminar but
not ramified vanes.

f Kieser’s Anatomic der PJlanzen, s. 160. “ The hairs of the Epidermis
“ consist of isolated rows of cells, simple or compound.”

|| This primitive black colour of the vane of the feather, with which the
original grey colour of white Birds, e.g. the Goose, Swan, &c. agrees, serves
as an additional fact in proof of the increased excretion of Carbon which
attends on the highly advanced state of Respiration in this Class. (Sec
§. 392.)

131

lias arrived at a certain size, it opens, the shaft protruding'
through it, though still covered by a horny elongation of
the quill upon its upper surface. The hairs now fall out,
(though in some accipitrine Birds they remain at the
extremity of the feather,) and are succeeded by the fibres
of the vane developed from the blackish mucous texture
already noticed : these, again, may be considered as smaller
feathers, being themselves furnished with lateral fibres,
which are peculiarly evident in those instances in which the
fibres of the vane are remote from each other, e. g. in the
tail-feathers of the Peacock ; and, likewise, almost always
on Down. When the feather is at last completely formed,
the vessels, as well as the membranous cells of the root of
the shaft, dry up ; and on opening the quill we find only
a husky, cellular tube, known as the pith. The quill like-
wise receives air, though not from the respiratory organs,
but by means of a small opening at its superior extremity.
The feather thus formed remains for one year, and is then
(like a milk by a permanent tooth) replaced by a new one;
which, however, is produced without any previous develope-
ment of hair.

§. 54?9. It is needless to say much of the form, colour,
and position of the feathers, as these are objects of Natural
History ; but it is remarkable that we can trace a transition
from feathers to hairs or bristles. We find it, for instance,
in the Cassowary ; where, except on the wings, the feathers
are to be viewed merely as weak shafts without vanes : and
evidently, also, in the tuft of black bristles found on the
breast of the Turkey, and representing an original tuft of
hair; which, instead of being supplanted by a feather,
increases to a considerable size, and is even covered by a
thin epidermis ;* lastly, there are also actual hairs on dif-

* The cutidc appears to be carried forwards with the feathers, though it
soon dries and falls off, producing the mealy powder between them.

K 2

132

ferent parts of' the body, as in the Vulture, Raven, See.
But even of true feathers the structure is very various ;
soft downy feathers, in particular, varying from others in
this respect, that, according to Nitzsch,* there are little
swellings on the lateral fibrils of the laminse of the vane;
thus resembling the structure of the stalk of many Plants.
The structure of the individual lamina* of the vane in the
larger feathers is likewise remarkable, inasmuch as the
superior edge of each is locked into the inferior edge of the
next following by a peculiar mechanism, each lamina being
furnished on its upper edge with laterally ramified fibres,
and on the lower with small simple fibres ; nay, on the
extremity of these fibres next the shaft, I see, in the Goose-
quill, for instance, merely a little ribband-like membrane on
each side of the laminae of the vane. By this mechanism
the laminae of the vanes shut so close into each other, that
the feather appears to form but one surface; and, conse-
quently, it is found peculiarly perfect in the feathers of the
wings and tail which serve for flight.

§. 550. Feathers are also distinguished by their degrees
of softness, by the more or less close connection of the
laminae of the vane, &c. ; thus, in the wings of the Pen-
guin, where we found the wing-bones broad and fin-like,
(^. 229.) the feathers are short, stiff, dense, and altogether
perfectly scale-like. Feathers vary, however, most mate-
rially in their colour ; which, being most brilliant in those
parts of Birds that are most exposed, — on the dorsal surface,
and particularly in diurnal Birds, and those of hot climates,
forms another instance of the great influence of light on
the production of colour. There is much, also, that is
deserving of notice in the change of plumage according to
age and sex, and more particularly the observation made by
Blumenbach, (Manual of Comp. Anat.) that the aged
* Voigt’s Neueste Magazin f. JVaturkunde, b. ii. st. 5.

133

females of several species, when the sexual functions have
ceased, assume the plumage of the male. Generally, colour
among vertebral animals reaches its highest point in Birds,
as in Insects among the invertebral, or flowers in the vege-
table world. Lastly, the aptness of feathers for receiving
an electric tension is remarkable,* as it is not improbable
that the prescience of weather may be connected with the
modifications of the electric state of the plumage produced
by atmospheric changes. We must mention, too, the
glands in the skin of Birds for the secretion of oil, as being
important for the support of the feathers. Besides that
each feather appears to be supplied with oily matter from
the point of the skin where it is inserted, the quantity of
oil necessary for rendering them impenetrable to water is
furnished by oil-glands upon the Sacrum ; which are par-
ticularly large in Wading and Aquatic Birds, and pour out
their oil by two fissure-like openings.

Section VII. Of the Skin in Mammalia.

§. 5.51. In the structure of the cutaneous organ the
Mammalia also present approximations to the earlier
Classes of Animals; the naked, slimy, or oily skin of the
Cetacea reminding us of that of Sharks and Rays ; the scaly,
armour-like skin of Armadilloes and Manis, of that of the
Amphibia; and the skin of Porcupines and Hedgehogs,
beset with quill-like bristles, of that of Birds. As to the
different strata of the skin, we may remark that the true
* Tiedemann’s Zoolofjic, b. ii. s. 155.

134

cutis is distinguished from that of the preceding Classes by
its much more considerable thickness, partly on the back
alone, and likewise in every part of certain animals, e. g.
the Elephant, Rhinoceros, Buffalo, &c. The cutaneous
muscles by which the bristling of hair, manes, &c. and
the corrugation of the skin, are produced, are usually
extraordinarily developed, and particularly so in the
Hedgehog, where these muscular fibres are the chief
agents in the rolling up of the body. As to the character
of the cutaneous muscles, we cannot avoid finding in
them a repetition of the muscular membrane, or sac,
which we frequently met forming the sole organ of
motion in invertebral animals. (§. 131.) The rete muco-
sum, which is ordinarily but little coloured, and the
cuticle, have the same relations as the corresponding parts in
the earlier Classes ; except that the change of the cuticle
here, as in Birds, is less evident, and is confined rather to
the change of the structures proceeding from it, i. e. Hair.
As in Man, the papillary texture is most perfect in the
organs of Touch, and is altogether wanting in the Cetacea,
as it was in Fishes. The most strongly marked colours of
the rete mucosum in this Class are found in the blue or red
callosities of the buttocks in several Baboons.

§. 552. The connection of the skin r *th the subjacent
muscles is effected by a cellular texture, which is peculiarly
distinguished by an extraordinary accumulation of fat in
the Palmata, in Swine, and in hybernating animals in
autumn : in some Bats, on the contrary, it admits air
(§. 430.); and in the Honey-Bear from the Cape, (Ursus
ifiellivorus,) according to SparmanN, quoted by Cuvier,
connects the skin but very little to the muscles. The
glandular apparatus of the skin appears to be wanting in
the Cetacea,* where, however, the deficiency is supplied

* Such must likewise be the case with Pangolins (Manis) and Aimadillocs.

135

-by tlie exudation of an oily mucus : in the other Orders it is
■essentially the same as in Man, where, as is well known,
the sebaceous glands secrete different matters in different
parts of the skin. We occasionally, however, find these
organs farther developed; in which case we can usually
discover in them repetitions of earlier formations. This
has been already remarked of the superior maxillary glands
of Sheep, Deer, Bats, & c. and of the anal glands: we have
also to notice similar glands in the sexual organs ; along the
lateral line of the body, as in Fishes, (§. 542.) ; on the
Sacrum, like the oil-glands of Birds, (§. 550.) ; or between
the claws, representing the secretion from the toes in many
Amphibia, (§. 545.) The first, according to Geoffro.y,*
is particularly the case in Shrews, and in a less degree in
Moles and some Rodentia, where we find a gland on each
side of the body, the secretion from which is discharged
upon the hair, and not by distinct ducts; and, like most
similar products, has a powerful odour. The sacral gland
is found in the Peccary (Sus Tajcissu ), where, according
to DaubentoNjF it is as large as a Goose’s egg. The
glands of the toes are found in particular in some animals
with divided hoofs, e. g. the Sheep, the Pigmy Musk, and
the Reindeer, and for the most part on the hind feet : the
excretory duct opens between the spurious claws or hoofs.

553. Flair, as is well known, is as commonly the
covering of the skin in this Cla§s, as Feathers in the pre-
ceding one ; and where it is wanting, as in the Cetacea,
the structure of the skin again approaches to that of Fishes
and Amphibia. I he varieties of Hair, in structure as well
as in colour, are extraordinarily great, and must partly be
left to the province of Natural History. The plumage of
the preceding Class is most closely imitated by the hairs or

* Mmoires du Mas. d'Hist. Nat. vol. i. p. 301.
f Burro n, Hist. Nat. vol. x.

1 36

prickles of the Porcupine, which we may consider as Fea-
thers consisting of a Quill and Shaft, but without a Vane,
and covered by a firm horny layer. The scales, too, of the
Armadillo, which terminate in a projecting edge, instead
of lying flat like the scales of Fishes and Serpents, appear
to resemble hairs connected together in laminae, and re-
mind us of the scale-like feathers of the Penguin. The
small prickles of the Hedge-hog, or the Echidna, form a tran-
sition from the stronger ones of Porcupines to the coarse hairs
or bristles which occur in the Pachydermata.* The bristles
of the Hog, by the double internal canal which they possess,
and the peculiar division of their points, remind us of the tufts
of hair of many inferior Orders of Animals, here as it were
inclosed within a cylinder. The ordinary Hair of Mam-
malia is essentially the same as that of Man : the finer kind
of Hair, on the contrary, viz. Wool, approaches more
nearly to soft feathers or Down, for, according to Nitzsch,
there are here the same little tubercles as in that case
(§. 549.); which even form the cause of the grey colour of
the hair in many animals, e. g . the Mouse, inasmuch as
under the Microscope the little tubercles appear black, and
the interspaces white.f Hair, like Feathers, grows from
its roots; and like them, when perfectly formed, is no
longer nourished, but falls out and is replaced by others.

§. 554. The colour of the hair in Mammalia is ordinarily
less brilliant and less varied than that of the plumage of
Birds, which is in fact hair at its highest pitch of develope-
ment. But here, as in the preceding Classes, we find that

* According to Cuvif.r, the hair of the tail in the Hippopotamus, as well
as in the Myrmecophaga jubata, is flattened : such, also, according to Blu-
menbach, is the case with the hair on the toes of the Porcupine and
Ornithorhynchus.

f As Beumenpach mentions, the mustaches of the Seal are also tuber-
culatcd or jointed.

the dorsal surface, exposed to the light, always presents
the most decided colours, whilst, on the contrary, the hair
of the abdominal surface almost always appears white: nay,
even the structure of the hair is more perfect on the dorsal
than on the abdominal surface; thus, Prickles are found
only on the back, &e. The powerful electricity of the
hair in several animals, e. g. Cats, has been already men-
tioned. (§. 407.) Lastly, the variation in the situation of
the hair, occasionally even in different sexes, is remarkable ;
thus, for instance, that the feet in so many Mammalia are
either naked or covered only with short hair, in the same
manner that the feathers in Birds do not ordinarily extend
to the feet : or that the tail of others, e. g. Rats, Opossums,
and Beavers, is covered with scales instead of hairs, in
which we recognize the incomplete conversion from the
Fish or Amphibium into the mammiferous animal : lastly,
the greater developement of hairs in particular situations,
e. g. on the snout, where they serve as organs of touch
(§. 343.); about the Eyes; on the neck, forming the mane,
which is wanting in the female of Lions ; on the tail,
where, as in the horse, they differ so much from that cover-
ing the rest of the body; &c.

§. 555. As to the other cutaneous productions of this
Class, the shields of the Armadilloes may be pretty accu-
rately compared to the shells of Tortoises, as they are to
be /considered as formed by several separate but closely
connected ossifications of the rete mucosum covered by
cuticle, d he scales of the Manis have been already noticed
as laminae of closely compacted hairs, (nail.) The scales
of the tail in Mammalia have been correctly compared by
Cuvier to those of the legs in Birds: in the smaller ani-
mals, however, they are already very delicate, and thus
form a transition to the regularly grooved epidermis on
the feet of so many Mammalia, and even on the hand of

138

Man. Nails agree with Hair in their chemical composition,
and in the mode of their growth. In the Carnivora, llo-
dentia, and Bats,# they resemble those of Birds and Lizards,
i. e. they are placed as pointed, cutting, horny sheaths, over
the extremity of the last phalanx. Broad, blunt nails,
inclosing the last phalanges, are called Hoofs ; and of these
we may remark that the nail or hoof is larger in proportion
as there are fewer toes visible, of which we have instances
in the Solipeda, and in the proportionally enormous claws
of the fore feet in the Two-toed Ant-Eater. The hair-like
structure is peculiarly evident in hoofs.

§. 556. It only remains to add something as to the
structure of Horns, of which we find three kinds in Mam-
malia. The horns of the Rhinoceros come nearest to the
structures just noticed; for in them, the mode of composi-
tion by the congregation of single, firm hairs, is so little
doubtful, that similar, though shorter, hairs, surround the
root of the horn, and that a transverse section of it evi-
dently displays the separate cylinders of hair. (See
Daubenton's representation of it in Buffon, Hist. Nat.
vol. xi. pi. VIII.) A second kind of horns is formed by
bony processes or cones, which arise after birth from the
frontal bone (§. 252.), over which a cuticular stratum is
extended, becoming callous and horny, and ultimately form-
ing a solid horny sheath, in the texture of which it is easy
to discover the individual hair-like fibres. Such are the
Horns of Sheep, Goats, and Oxen. The third kind of
Horns is found in the Antlers of Deer, in which we have
already noticed the intimate mixture of horny and bony
substance, as well as the remarkable sympathy between
them and the male sexual organs. (§. 251.)

§. 557. If we review the history of the developement
of the skin, in order to discover how far this structure is

* Here, as in Birds, the flying extremities liayc a nail on the Thumb alone.

131)

distinguished in Man, we shall find that in the lowest stages
the cuticle is as yet similar to the intestinal membrane ; that
as a secreting mucous membrane, it is little calculated for
forming the seat of an acute sense of touch ; and farther,
that it is in part concealed either by earthy shells, or in
superior animals by scales and shields: subsequently, when
respiration exists more perfectly throughout the whole
body, we find the productions of the skin, hairs, bristles,
and feathers, so copiously developed, that the cutaneous
sense is impeded as well from this cause, as from the thick-
ness of the skin, the deposition of fat below it, &c. As
regards his cutaneous organ, Man is intermediate between
the excessive softness of the mucous cuticle of the Mollusca,
and the induration of the skin in Insects, or its plumage
in Birds: his skin is more delicate and more copiously
supplied with Nerves than that of the other Mammalia;
and in nearly all parts has only few hairs, and those so soft
as not to impede the cutaneous sense. The more copious
production of hair on the surface of the scalp appears to
me explicable by the remark already so often made, viz.
that all the structures belonging to the skin are most per-
fectly developed on the side turned towards the light
(§. 554.) : consequently, as by the erect posture peculiar to
Man, the cranial surface is that which is most absolutely
exposed to light, the hair must be more developed there
than in other situations ; whence, also, I am farther led to
conclude that the hair of the head would in itself afford a
most convincing proof that the erect posture is that most
suited to Man, even if the grounds for that opinion already
pointed out had left any doubt on the matter. The Beard
may be viewed as a repetition of the tentacular hairs on the
snout of many Mammalia, and its perfect developement in
the male sex as a consequence of the intensity of the deve-
lopcment of Respiration and of the extremities, which in

140

brutes coincide in the same manner with the perfection of
hairs and feathers. The hair of the Pudenda and Axillae,
lastly, appear to be consequences of the more copious
glandular secretion in those situations, which in other
animals we found frequently connected with a greater
developement of hair. (§. 552.)

§. 558. The Nails, the only horny processes of the skin
that remain in Man, are in him comparable rather to scales
than to claws or hoofs, and instead of blunting the fine
feeling of the organs of Touch, appear rather to contribute
to render it more acute. In Man, too, the skin is no longer
so moveable as in other Mammalia, in which that mobility
reminds us of the muscular cloak of Mollusca and W orms,
whilst its diminution appears favourable to sensibility. As
to colour, we found that it reached its highest point in the
two Classes (Insects and Birds) most distinguished for
Respiration and Motion, whilst the other Classes either did
not attain, or again retroceded from, the same stage. The
latter is the pase in Man, where the skin in the most per-
fect Races* is almost colourless, and reddened only by the
subjacent blood ; a phenomenon, the cause of which has
been admirably shewn by Goethe, f when, in considering
the colour of Mammalia, he says, “ The variegation of
44 certain uncovered parts in Apes with elementary colours,
“ is a proof of the remoteness of such beings from perfection:
44 for we may venture to assert, that in proportion as any
“ creature is more perfect, its material elements are more
44 intimately compounded, and that the more intimately the
44 surface is related to the interior, the less appearance will
44 there be of elementary colours upon it ; because, where

* It will be seen, from what follows, how far the less strongly marked
colour must indicate the superiority of the Race; and for more information
on the topic, Goethk zvr Farbciikhrc, b. i. s. 217, may be consulted.

| Loc. cit. vol. i. p. 245-46.

i4i

« all should combine to form a perfect whole, there must
« not be any local or specific distinctions.” The cutane-
ous organ in Man is, therefore, distinguished by a higher
import in this particular ; and farther, inasmuch as by the
capability of changes in the state of its colour it offers a
reflection of the various conditions of mental feeling, ap-
proaches near to the nobler organs of sense, e. g. the Eye,
which we have already noticed with relation to the same
point. (§. 402.)

II. Of THE VARIOUS FORMS OF THE RESPIRATORY

Organs.

§. 559. The Respiration of Animals, inasmuch as it
consists in the mutual action upon each other of the indivi-
dual and the element surrounding it, (§. 529.) renders
necessary the free and constantly renewed access of that
element to the respiratory organs. This element is air,
and is applied either immediately, or mediately by means-
of water, which in that case must itself, as it were, have
respired air, and must be thoroughly penetrated by it, (not
merely mechanically,) in order to be fitted for supporting
the animal respiratory process. But in order that the
access of these elements, or rather of the single one, Air,
may be permitted to the organs of Respiration, the latter
must originally be placed on the surface of the body:
nay, the cutaneous surface itself appears at first as the sole-
respiratory organ ; and it is only in a more advanced state
of developement of the animal body that peculiar struc-
tures, air and water cells, (Lungs, Air-vessels, and Gills,)

appear, which, however, may be considered collectively as
processes of the skin, ramifying1 sometimes internally, some-
times externally. That we ordinarily find a complete
apparatus for motion combined with the respiratory function,
or, as is probably the fact, that the first and primitive
animal motion is purely respiratory, is a fact, of which we
find the cause in the principle that Respiration has the
same relation to the Vegetative, as Motion to the Animal
Sphere (§. 20.) ; and that, consequently, the less animal
and vegetative life in the inferior gradations of organization
are distinct from each other, the more perfectly simulta-
neous must be the progress of the developement of Respi-
ration and Motion on the one side, or on the other of
Assimilation and Sensibility, and the more completely
must they shew themselves connected in the higher organi-
zations. Instances of the one kind are afforded by the
Mollusca with highly developed organs of Digestion and of
Sense ; and of the other by Insects, in which the respira-
tory and locomotive organs are developed in the highest
possible degree.

A. Respiration of Animals without Spinal
Marrow and Brain.

Section I. Respiratory Organs of Zoophytes.

560. What we before remarked of the most imper-
fect animal formations, viz. that the whole surface must be
considered as a respiratory organ, applies to the lowest of
these originally water-breathing beings. Of this we find

143

the proof in the fact, that though there can be no doubt of
the actual respiration of these animals, yet we are unable
to detect any peculiar respiratory organs in the uniform
substance of their bodies. IIow far the current of fluid in
the arms or tentacula of Polypes and other Zoophytes, (§^
59, 66.) or the contraction and extension of the body gene-
rally, may be subservient to Respiration, is a point that has
been already noticed, (§. 60.) and which, though in many
respects probable, has not yet been established on sufficient
observations. It is in the Medusae that more distinct
organs for this function appear : in several species we find
peculiar sacs on the inferior surface of the bod)'', which,
during the expansion of the body» admit water through
certain apertures, (Tab. I. fig. IX. A. c. c.) and again
expel it during the succeeding contraction : in other in-
stances, as the Physsophora and Rhizophysa, there are
air-bladders at the upper part of the body, which, though
usually viewed rather as helps to locomotion, like swim-
bladders, may probably also be connected with the respira-
tory function. In every process of Respiration there are
two distinct phenomena ; the one consisting in the access
of oxygen to the fluids of the body, the other in the eva-
cuation from them of the volatilized elements of the body,
Carbon, Azote, and Hydrogen. We usually find both
processes united in a single organ, e. g. the Lungs of Man
and/many other animals ; not uncommonly, however, they
are more or less separated; and in particular, as we shall
find to be the case with the swim-bladder of Fishes, there
is frequently an excretion of gaseous matter in certain
situations very remote from the Organs of Respiration.
The air-vesicles in the animals before mentioned may
probably be derived from secretions of such nature, inas-
much as it is unlikely that true respiration of air should
occur in such low stages of animal existence.

<§• 561. In tlie Eehinodermata, where the surface of the
body is frequently covered by leathery or calcareous shells,
internal respiratory organs appear to be more necessary ;
and consequently, according to CuviEit, there is in the
Holothuriae a kind of Cloaca (§. 434.) communicating with
ramified tubes, which, being fitted for admitting air or
water, may be intended for the respiratory process.* In
this, as well as in several other species, consisting exclu-
sively of the lower gradations of organization, we conse-
quently find the intestinal and respiratory functions so little
separate, that the respiratory organ appears even to form a
part of the intestinal canal. It is remarkable, and, at the
same time, perfectly correspondent to what has been already
said of the mutual opposition of Digestion and Respiration,
1st, that the digestive cavity (the Stomach) is never a
repiratory cavity; and, 2d, that of the two remaining por-
tions of the alimentary canal, the (Esophagus and Intestine,
the latter by far the most frequently assumes the respira-
tory function, with which fact it perfectly agrees, that the
latter is in its nature more secretory and excretory :f but
if, notwithstanding, we occasionally find the upper portion
of the alimentary canal assuming this function, and the
respiratory organs in the superior animals ordinarily con-
nected with its oral extremity, we must reflect that the
(Esophagus is the first and frequently the sole portion of
Intestine, and consequently that it must be originally ex-
cretory as well as ingestive. Lastly, it is worthy of notice
that the organizations, by means of which intestinal respi-

* The water that has been respired is expelled from the anus with some
force, and forms tire means by which the animal moves. (See Oken’s
Zoologie, b. i. s. 350.)

f In describing the intestinal canal, we have already frequently indicated
the close relation existing between the extremity of the Intestine and the
organs of Respiration.

145

ration takes place, are very frequently indicated or repeated'
in the superior species; of which we find instances in the
various expansions of the intestine already described, and
occurring sometimes about the Pharynx and (Esophagus, as
Laryngeal sacs, crops, &c. ; or in the intestine, as Colon,
Cloacae, &c.

In the Echini and Asterias the Tentacula (§. 66.) appear
to absorb water for Respiration: such respiratory Tentacula
we may consider as the first indication of Gills, in the same
manner as the cavities of the Medusae of Lungs. Even in
the Actinia we already find this ingestion and evacuation of
Water in the Tentacula, which here are placed about the
mouth. (Tab. 1. fig. X. A. b.)

Section II. Respiratory Organs of the Mollusca.

(A.) Acephala,

§. 562. We find more decidedly expressed in this, as
well as in several of the succeeding Classes, the fundamental
distinction already indicated in the preceding Class between
the different forms of the respiratory organs, viz. between
Gills, articular, and cavities, intestinal Organs for Respi-
ration. Among the exclusively water-breathing Acephala,
we find in the Ascidise, where the leather-like case inclosing
the body appears to render internal respiration necessary,
a large respiratory cavity, (Tab. II. fig. II. d.) which being
longitudinally folded, forms the innermost, and at the same

VOL. II.

time most delicate, of the three sacs 70.) of which the
animal appears at first sight to be solely composed : from
its lowest part the (Esophagus, as already mentioned, (§.
435.) arises. In a large species, very closely connected
with the Ascidia microcosmus , lately examined by Cuvier,
and which I had an opportunity of dissecting in 1815,* I
found that this sac, which commences by a trumpet-shaped
dilated mouth-piece, (Tab. II. fig. II. a.) and is furnished
at its entrance (c.) with a valve and a circle of laminae, also
presents, in addition to its opening into the (Esophagus, a
lateral opening furnished with valves, and hitherto unno-
ticed by any anatomists. (Fig. 2, a. 2, b.) The fact was
the more interesting to me, as it afforded the means of
explaining the phenomenon described by several writers,
and noticed, f though discredited, by Cuvier, viz. that this
animal has the power of rejecting the respired water not
only through the mouth but also through the anus. These
remarkable beings must receive their nutriment from the
animal substances taken in with the inspired water; for
even in a very small individual I found the Gill-sac occu-
pied by a Punger ( Cancer pagurus) scarcely less than half
its own size. There is much that is peculiar in the deve-
lopement of this respiratory cavity ; for in the young animal
it can be distinctly recognized as an integral part of the
intestinal canal, and as the body increases this originally
crop-like dilated part (Tab* II. fig. IV. b.) gradually attains'
a more considerable extent, and varies in structure from
the intestinal canal in having exceedingly delicate and

* An investigation, during which it was not possible that I could be ac-
quainted with Cuvier’s Monograph on this Animal, ( Menu du Mus. d' Hist.
Nat. 1815, and which was subsequently published in Meckel’s Archiv. b.
ii. h. 4.

f Log. eit. p. 10. Rondelet long since depicted the animal ejecting
water from both openings.

1 47

transparent parietes, — in a word, diverges more and more,
from the Intestine.* f

§. 563. In most other Acephala, and particularly those
provided with shells, we find the respiratory organs with the
structure of Gills, though with infinite variety of form. The
internal cavity of the Salpse, furnished with a single branchial
lamina, appears to constitute the transition from the Ascidise
to the Teredines, where there are two elongated branchial
laminse above the Intestine and within the tubular cloak,
to which the water has access and egress by means of two
tubes placed at the posterior extremity of the body. (Tab.
II. fig. XV. i. i.) In Bivalves there are ordinarily four
large branchial laminse protected by the branchial mem-
brane (cloak,) and operculum (shells), and also in many
instances some small gill-like laminse about the mouth. In
the Fresh- water Muscle, (Unio pictorum,) for instance,
there are four small gill or lip-like laminae about the mouth,
(Tab. II. fig. VII. b. b.) besides the two large pairs of
laminse extending from the dorsal surface of the animal,
partly at each side, and partly behind the foot. (Tab. II.

* , See a fuller account of this developement, unnoticed by Cuvier as well
•as by earlier writers, in the above-quoted Essay in Meckel’s Archiv.f. Phy-
siol. b. ii. h. 4.

f Cuvier describes the opening at the bottom of the branchial sac as
being the mouth of the animal, the respiratory cavity being situated in front
of it. / In general its surface is uniform, but in certain species is disposed in
deep and regular folds, forming the first indication of the four branchial
lamina; of the Bivalves. The structure of the membrane is also peculiar, and
evidently connected with its function as a respiratory organ, consisting in an
infinity of small vessels crossing each other at right angles, and forming qua-
drangular interspaces ; which, under the microscope, are seen to be still more
minutely subdivided in the same manner. The little vertical vessels are
seen to arise from transverse branches, which, in their turn, communicate by
each extremity with two vertical trunks, placed at opposite sides of the sac,
and supposed respectively to represent the branchial artery and vein. ( Ms -
moire sur If a Ascidies, p. 11.) — Translator.

L 2

1 48

%'• VU* d. dA fig. VIII. e. cl.) The latter laminse are
united superiorly, and form a septum between the lower
space, which receives the water through the great aperture
of the cloak, (fig. VI. g.) and contains the gills them-
selves, and the superior passage opening into the anal
tube of the cloak, (shewn by the probe in fig. VIII.) In
a living Bivalve it is easy to observe that the water gains
access to the branchial laminse by the fissure in the cloak,
(§. 126.) and escapes by the anal tube, which serves also
to evacuate excrement and ova. It has not, however,
been hitherto noticed, that this current Is uninterrupted,
and that thus these animals, when not too deeply im-
mersed, form an eddy on the surface of the water. But,
as in almost all other animals, the influx of air or water to
the respiratory organs is intermittent, the simultaneous and
continuous current into the fissure of the cloak and out
of its tube, of which I have satisfied myself by numerous
observations, must depend on a very peculiar mechanism,
which consists chiefly in the muscularity of the cloak, but
partly, also, in the mobility of the gills themselves ; and
may be compared to the mechanism of certain bellows,
which produce an uninterrupted current of air by means of
double bags.

§. 564. It is to be remarked, farther, of the large
branchial laminse of the Fresh-water Muscle, that both
pairs consist of an intertexture of vessels arranged in a
rectangular lattice-work, and covered by a delicate mem-
brane, whilst the two external are distinguished by a struc-
ture which merits a particular description. Above eacli
external lamina of the gills is a duct proceeding from the
posterior part of the foot towards the anal tube, long ago
described as an oviduct by OKEN,f and having on its low^er
surface a long row of openings placed transversely, (Tab.-
f Gutting, gel. Anzcigen, 1806.

149

II. fig. XI. q.*) and forming the entrances to the cells or
compartments of the gills themselves. T hese compart-
ments are all arranged vertically in the gill, and separated
from each other by partitions : they appear as though they
originated from the mutual recession of the two membra-
nous surfaces of the gill, which remain connected only by
the vertically disposed vessels that give rise to the septa :
they serve for the reception of the ova, which, coming
from the ovary placed within the foot, and not by any means
formed in the gill itself, are, however, lodged there, and
there receive their farther developement, as in a Uterus.
This is a remarkable instance of the connection between the
sexual and respiratory functions, of which we shall subse-
quently meet with many others.

§. 565. Of the various forms of the gills in other
Bivalves I will here only mention, that in some they are
not laminar, but consist of separate fibres or vessels, e. g.
in the Genus Lingula ; where also the little branchial or
labial laminae of the mouth are developed, so as to form two
rolled and ciliated arms. More peculiarly remarkable, how-
ever, are a kind of branchial skeleton found in the Tere-
bratulae ;f and on account of its coincidence with the
situation of the gills in the Crab, — the position of the same
part in the Barnacle (Lepas anatifera), where we find two
small pyramidal branchial laminae at the root of the first of
the six pairs of horny tentacula.f;

f Oken’s Zoologie, b. i. s. 250.

| See Cuvier in the Mm. du Mus. d'Hist. Nat. t. ii.

150

11. Gasteropoda.

§. 566. The variety of the respiratory organs in this
Order is considerably greater than in the preceding, parti-
cularly as many of the Genera belonging to it breathe air.
Gills, the organization which approaches most closely to that
of the preceding Order, are found in by far the greater
number of the Gasteropoda, and assume, particularly in the
marine species, the most diversified forms. Thus, for
instance, in the Clio we find laminar gills, reminding us of
the labial branchial laminae of the Bivalves, placed about
the mouth, and which, here as well as in several other
species, serve as external organs of motion. (§. 132.) In
the Glaucus, also, we meet with fin-like gills cut out like a
fan, and three in number on each side, the anterior ones
being largest. In the Thetis the gills appear as fourteen
distinct tufts on each side of the back; in the Tritonia -
they run in a circle around the edge of the body; in the
Doris they are placed as a range of tufts around the anus ;
and in the Aplysia, as well as many other Genera,* we
observe that the gills are placed close to the anus, in the
same manner that in the Acephala we commonly saw the
water that had been respired ejected through the anal tube.
We do not observe, however, any peculiar mechanism for
the motion of these gills, and respiration appears to be
effected merely by their floating in the water.f

* The different forms of these respiratory organs are well described by
Cuvier, in the admirable series of Essays on the Anatomy of the Gastero-
poda, which he has given in the Annales du Mus. d'Hist. Nat.

f In the Clio borealis the branchiae consist in the oval wing-like processes
below the head, as is proved by the minute ramification of vessels upon themf
and by the connection of those vessels with the heart and internal vascular
system. In the Pneumo-dermis, though there are similar wing -like organs,

§. 567. In the Aplysia camelus these branchial tufts
already recede under a small membranous cloak, and are
even covered by an incomplete operculum, (§. 129.) a rem-
nant of the shell of the Bivalves, — thus forming a transition
to the testaceous Gasteropoda, e. g. Buccinum, Strombus,
Murex, Cyclostoma; where we find a capacious cavity
formed by the cloak, and concealed within the shell, gene-
rally having the gills projecting into it in a pectinate form.
In the Cyclostoma viviparum , (Helix vivipara, L.) the gills
form three rows of fibres arranged in a pectinate manner,
(Tab. III. fig. X. XI. e.) with their extremities project-
ing but little below the edge of the cloak, and having in
their vicinity the rectum, the duct for the discharge of
mucus, and the female sexual organs. In the other
Genera, e. g. Murex and Strombus, the edge of the cloak,
nearly as in many Bivalves, (§. 563.) is elongated into a
tube conducting the water to the branchial cavity ; and
which, though merely indicated in the Cyclostomata by a
fissure, is here lodged in a peculiar groove of the shell.
The pectiniform gills are here usually double, but in such
a manner, that one, according to Meckel,! is twelve times
smaller than the other, and appears only as an insignificant
rudiment.

§. 568. Lastly, we find the gills totally disappearing
from these cavities, the vessels which contain the fluids
thayt are to be exposed to the influence of the air being
expanded in the form of a delicate net-work upon the inner
surface of the respiratory cavity ; and water no longer suf-
ficing for the exercise of the respiratory process, the animal

there is not a corresponding vascular net-work, and the branchiae are formed
by an elliptical cord placed vertically, and consisting of a number of little
laminae. (Cuvier, Mcmoires sur les Mollusqucs. ■ Paris, 1817, 4to.)— .
Translator.

f Notes to his translation of Cuvier’s Comp. Anat. vol. iv. 269.

152

requires air itself. Nevertheless, several of these animals,
e. g. Lymnsea sive Helix stagnalis, Bullinus, Planorbis, &c.
live in water, and, consequently, must come frequently to
the surface in order to procure air : they appear, also, to
employ the respiratory cavity filled with air as a Swim-
bladder to facilitate their swimming, thus reminding us of
the air-bladders of many Zoophytes (§. 560.) Others, on the
contrary, (Helix and Umax,) live altogether in air. The
Cloak in all those which breathe air, by its connection with
the neck, forms a kind of collar. (Tab. III. fig. I. e. e.)
On the right side of it is a foramen (f.), on the edge of
which open the anus and canal for the discharge of mucus,
and which can be closed or expanded by means of circular
muscular fibres, so as to favour the ingress or egress of air
to and from the respiratory cavity (Lungs). The cavity
itself (fig. II. h. 1.) is lined with a blackish mucus, and
from the minute ramification of vessels upon its parietes,
(fig. III. h. g.) presents a very beautiful spectacle. In
Slugs, the respiratory cavity is placed on the right side of
the back of the animal, is arched over by a horny Oper-
culum (§. 129.), terminates in a contractile orifice, and
altogether agrees essentially with that of Snails.

(C.) Cephalopoda.

§. 569. Although some Sepise are capable of living in
air for some days,* yet water must be considered as the
proper element of the whole Order ; and accordingly, we
here again find Gills forming the proper respiratory organs.f

* Oken’s Zoologie, b. i. s. 343.

-j- How animals with Gills should also be able to breathe in air becomes
less obscure in proportion as the supposed distinction between the Respira-

153

In the Sepise there are two such, (Tab. IV. fig. I. h. h.)
one on each side of the peritoneal sac (n.) surrounding the
viscera. Each Gill is formed by the Branchial Artery and
Vein placed at its edges, and which are connected by
numerous detached transverse vessels. The transverse
vessels are finer and more numerous in the S. officinalis;
in the S. octopodia fewer, but larger, and with flocculent
edges ; but invariably connected to the inner surface of
the Cloak by means of a membranous ligament. (Tab. IV.
fig. II. v.) This Cloak, as well as the Infundibulum, ag
it is called (anal tube, §. 442.), promote the ingress and
egress of the water to and from the floating Gills, and in
fact form the respiratory mechanism. The Cloak (fig. I.
i. i.) which, as already observed (§. 134.), surrounds the
abdominal viscera in the form of a fleshy sac open above,
appears by its dilatation to permit the current of water to
the Gills, and by its contraction to expel it through the
Infundibulum (fig. I. a.) ; whence it will be seen that the
respiratory motion is very similar to that of the Bivalves,
where the water in the same manner enters through a fissure
in the Cloak, and escapes through the anal tube. In the
S. octopodia I find, moreover, a fleshy septum in the cavity
of the Cloak, arising from the anterior side of that muscu-
lar sac, and connected posteriorly, (where it incloses the
Rectum,) to the upper part of its dorsal portion, and of the
peritoneal sac, so that, consequently, there remains inferiorly
a free communication between the two halves of the cavity
of the Cloak. (Fig. I. g. fig. II.*.) This Septum must
evidently contribute to produce a more efficient contraction
of the cavity of the Cloak.

§. 570. I must not omit to mention that several obser-
vations appear to prove that there are also collections of

tion of the inferior and superior animals disappears. (See Nasse on Respi-
ration, iti the 2d vol. of Meckel’s Archiv.)

air, more particularly in the peritoneal sac of the Sepise :
to this head belong the rapid ascent of the Sepite in the
water, observed by Tilesius* to be accompanied by a
swelling of the body ; the escape of bubbles of air when
the animal dies or is opened; and lastly, the porous structure
of the Os Sepise,f (§, 133.) which contains air within its
cells. These collections of air, however,, can as little be
admitted as proofs of actual respiration of air as those in
certain Zoophytes, but rather as dependent on the separa-
tion of aeriform matter from the blood, as expirations.

Section III. Respiratory Organs of the Articulata.

(A.) Vermes.

§. 571. Although Respiration in this Class gradually
arrives at the greatest possible degree of developement,
yet, in the first order, we find whole series of Genera in
which there is no peculiar organ assigned to that function,
nay, in which it is still even doubtful whether Respiration
is performed in any way : this is particularly the case with
the Intestinal Worms. Whoever considers, however, that
it is scarcely possible to conceive that any animal organiza-
tion can be perfectly excluded from a mutual influence on

* De Respiratione Sepia Offic. p. 64. 68: observations which, as he
mentions, have been made also by Rondki.f.t, Le Cat, and Monro.

f Hence the Os Scpi;e, as Swammerdam states, is so light, immediately
after it is taken out of the animal, as to float upon water.

155

and by the atmosphere, will find a difficulty in admitting
this supposed perfect absence of Respiration, and will
rather be inclined to think that these beings, formed and
living within other animals, are related with the atmosphere,
i. e. breathe by the intermedium of the bodies in which
(as in their proper soil) they are rooted. * Consequently,
as these animals are nourished only as individual parts of
the body in other instances (e. g. a piece of Intestine, a
Vessel, &c.), so also, they breathe in the same manner as
such individual parts, viz. in consequence of being pene-
trated by the fluids of the greater organism which has itself
respired. Hence, the same thing appears to me to take
place here as in the water-breathing animals, which also do
not ordinarily come in contact with the atmospheric air as
such, but perform the respiratory function by the inter-
medium of water through which air is diffused.

§. 572. The respiratory organs, on the contrary, are
more distinct in most of the extraneous Vermes, and par-
ticularly in those with red blood: we there, as in the
Gasteropoda, find both kinds of respiratory organs, viz.
cavities, or Bladders, and Gills. The former is the case in
the Dew- Worm and Leech. In the Dew- Worm (Lum-
bricus terrestris,) we find, as was described even by Willis,
a row of apertures, one of which is always visible, placed
along the back at the anterior edge of each segment of the
body. In the middle of the body I find these apertures
(Stigmata) particularly distinct, (Tab. V. fig. IV. b.)
whilst they seem gradually to disappear towards the head.
The internal respiratory vesicles are placed as pairs of
whitish sacs between the skin and Intestine through the
whole length of the body, are peculiarly developed in the
central and posterior portions of the body, (Tab. V. fig.

* RudOi.phi, ( Enloznorum Hisloria Nat. vol. i. p. 213.) also, decides
in favour of the respiration of these animals.

156

111. B. e. C. c.) but become smaller towards the head,
until about the space between the Pharynx, Head, and
Stomach, where they suddenly undergo a considerable
increase of size, no longer appearing in the character of
respiratory but of sexual organs ; of which more hereafter.
To these last appear likewise to correspond from three to
four pairs of abdominal stigmata, which, also, should be
considered rather as sexual than respiratory apertures.

§. 573. In the Leech (Hirudo medicinaUs), we find, in
the same manner, on each side of the abdominal surface,
a row of minute Stigmata forming the entrance to the
whitish, roundish, respiratory vesicles, which are lined
internally by a vascular mucous membrane, and situated
between the Skin and Intestine on each side. (Tab. V.
fig. VIII. h. fig. X. b.) We find Gills as respiratory
organs in many marine Worms, and presenting great
varieties in form and number. Sometimes, for instance,
they are placed at each side of the mouth, almost like the
Arms of Polypes, as fans or feathers, occasionally of a
spiral shape : so, for instance, in the Worms living in
calcareous tubes, e. g. Serpula, Spirillum. Sometimes, as
in several Gasteropoda (Tritonia, Thetis, &c.) they are
placed as tufts at, each side of the body ; as, for instance,
in the Lob-worm (Lumbricus marinus ), which has a row
of sixteen branchial tufts at each side of the body. Lastly,
in the Aphrodite aculeata , we have a peculiar form of
respiratory organ ; for here, a matted covering of hair,
open posteriorly, protects the back, the water pouring in
below it, and serving for respiration by being thrown upon
the projecting lateral coeca, or rather arcades of the intes-
tinal canal, (see §. 445.) in the same manner that in
Ilolothurue, Ascidue, &c. we found a portion of the ali-
mentary canal assuming the respiratory function.

' ' ' ^ ’ •

(B.) Crustacea.

§. 574. Here again we find the respiratory organs as
trills only ; but, as in several Gasteropoda, so far different,
that in some Genera they are placed externally, in others
are withdrawn more towards the internal part of the body.
The former is the case in the Genera Squilla, Apus, and
Branchiopus, which, in this as well as other respects,
approach to tlie Worms with external respiratory organs.
The Gills are here placed, and occasionally in great num-
bers, as external extremities, or swimming fins, (§. 142.)
on the posterior part of the body, or tail, which is articu-
lated completely in the manner of worms. In the Squillae,
they are formed by the Gills which consist of depending
fibres inclosed between two larger laminae: in the Squilla
mantis , for instance, there are five such pairs of fins.

§. 575. On the contrary, there are internal Gills in the
true Crabs and Cray-fish. In the common Cray-fish the
Gills compose thick, upright bundles of fibres, turning
somewhat backwards, and attached to a branchial lamina
at the roots of the legs, nearly in the same way that in
the Lepas the Gills were attached to the roots of the large
articulated Tentacula. .(§. 565.) These branchial tufts
(Tab. VI. fig. VIII. b. c. d.) are separated from the cavity
of the abdomen by a horny, flexible, white, and transparent
septum (fig. IV. q.), which consists of separate laminae like
Ribs. These proceed from the abdominal surface, where
there is a kind of vertebral column, in which the anterior
part of the chain of Ganglia is contained like a Spinal
Marrow, (see fig. I.) ; they terminate, however, without
being attached, under the thoracic plate, the lateral portions

of which, consequently, (like the Shell of a Bivalve, see
§• 1^2.) form the external covering of the Gills. Between
this Thorax, then, and Operculum, (Thoracic plate,) the
branchial tufts are found resting on the scapular-shaped
horny laminae, which are the internal termination of each
leg, (§. 144.) receiving motion from them, and forcing out
the fluid (Water or Air) which enters under the Opercu-
lum, at the anterior edge of the thoracic plate on each side
of the mouth. Of the flns observed on the under surface
of the tail in the Squillse, we find in the Cray-fish only
some little fii>like laminae remaining, which appear to be
connected with the sexual rather than the Respiratory
Organs.

(C.) Insects.

§. 576. Almost all the modifications of the respiratory
organs, which occur separately in other Classes and Orders
■of Animals, present themselves in this Order, where the
function of Respiration generally reaches its highest pos-
sible degree of developement. External and internal Gills
(Pulmonary and Branchial cavities), and Tracheae, are the
means by which its various species respire either air or
water, or even through the medium of the juices of other
animals.

Among the Gnathaptera, the Onisci, Scorpions, Spiders,
&c. approach nearest to the preceding Order, as regards
their respiratory organs, breathing air or water by means
'of Gills; though in Spiders we find also mere blind air-
‘cavities or sacs (Stigmata). In the Millepedes, on the
contrary, there are already Tracheae and Stigmata.

§. 577. lit the Onisci the excellent investigations of
Treviranus* enable us to recognize the following parts as
respiratory organs, in which we cannot fail to observe an
approximation to the' gills of the Squillse. (§. 574.) In
the common Woodlouse (Oniscus asellus,) the gills are
situated below three pairs of valves at the posterior part of
the abdominal surface in front of the anus, and behind two
pairs of valves which cover the genital parts. The six
gills are membranous quadrangular laminae, which rise and
sink, (about 50 to 60 times in a minute,) and are suited
only for respiring air. In the Oniscus aquaticus there are
also three pairs of gills provided with opercula ; but instead
of being overlapped one by the other posteriorly, they are
placed one below the other, so that the uppermost oper-
culum at the same time conceals the inferior ones. These
gills are also in constant motion, but breathe water. Scor-
pions approach nearer to the remaining Insects, Stigmata,
as was the case in some Worms, being found on both sides
of the abdominal surface. In the European Scorpion Tre-
viRANUsf found four such Stigmata on each side leading to
a branchial cavity, the gills themselves being formed by
a great number of delicate, half-round, white laminae at-
tached to the horny ring of each Stigma. In Spidersf
( e . g. Aranea diadema) there are four pairs of stigmata at
the sides of the thorax above the roots of the legs, and four
similar pairs on the upper side of the abdomen. They
are, however, merely blind pits (Tab. VII. fig. VI. A.)'
without air-passages or gills. There are some imperfect
indications of similar Stigmata on the abdominal side.
Lastly, in addition to these Stigmata there is an openings

* On the internal structure of Apterous Insects, in his Vermischie Schrijten •
Anatom, u. Physiol. Inhalls, b. i. Gotting. 1816.

t Ueber d. Ban der Arachnxdcn , s. 7. J Treviranus, l. e.p. 23>— 2&-

oh the abdominal surface above a little transverse fold, and
on each side of the sexual organs ; which, nearly as in the
Scorpion, leads to a branchial cavity, the gills of which are
white, mucous, and composed of several laminae. (Fig*

VI. B.)*

§. 578. The respiratory organs are altogether different
in the remaining Orders. In them we find the body cal-
culated for respiring air alone, which is effected by means
of respiratory tubes penetrating every part in the form of
extremely minute ramified vessels carrying the included air
to all the organs. Even where these Insects live in water
they respite air, which generally adheres all round their
bodies, (as, for instance, in Water-beetles, and also Water-
spiders,) probably by means of the little bristly hairs, which
by their oily nature prevent the access of the water. Such
Insects, therefore, always swim in the centre of a bubble
of air,f and therefore with the more facility, — Respiration,
consequently, here serving to facilitate Motion, as Motion

* M. Marcel de Serres (Memoir es du Museum, vol. v. p. 94) describes'
the respiratory organs of true Spiders more precisely as being composed of
two oval pulmonary sacs, each having a single Stigma opening at the inner
side of the lower part. These sacs are formed of a thick, white, and flexible
membrane, from tbe surface of which project several parallel trhnsverse folds
or laminae. In the Genus Phalangium, on the contrary, respiration is per-
formed by Tracheae, of which there are three principal trunks, viz. two
superior, which communicate directly with the two Stigmata at the sides of
the Corslet, and with the common central trunk. In the parasitic Insects,
Pediculus and Ricinus, there are two orders of Tracheae, the one arterial, or
ramified; the other pulmonary or vesicular, and serving as reservoirs of air.
The former are regularly arranged at some distance from each other on the
lower parts of the body, communicating with the Stigmata by transverse
branches, and also with the vesicular tracheae. (De Serres, Memoires du.
Museum , vol. v. 126.) — Translator.

f It is remarkable how, according to Nitzsch, (On the Respiration of the
Jlydrophilce, in Reil’s A rchiv. b. x. s. 4-40.) they renew the air in this
bubble by alternately elevating and depressing the Antennae.

ltil

in so many other instances promotes Respiration. Insects
which live in water without having an air-bubble of this
kind about them, as, for instance, the Nepa, have respira-
tory tubes at the anus in the form of long bristles, by
means of which they procure air from the surface. In all
these Insects, the air penetrates the body by peculiar
openings (Stigmata), and is diffused through it by means
of air-vessels. These statements apply, however, to the
perfectly formed Insect only ; for in the Larva the respira-
tory organs are very generally formed after an inferior
type, either respiring water as Gills,, the Stigmata being
consequently wanting, or else the animal being altogether
without any air-vessels.

§. 579. We have next to examine somewhat more
precisely the ordinary structure of the respiratory tubes and
stigmata. The latter, as in Vermes and the Gnathaptera,
are usually found on each side of the body, and though in
very various numbers, commonly more developed on the
thoracic than on the posterior part of the body, and always
in pairs, i. e. one on each side of each segment of the
body. Their form most closely corresponds to that of the
fissure-like openings by means of which Plants, and parti-
cularly the leaves of Plants, breathe.* These , Stigmata
are also usually found as fissures, so that we observe two
lips, an anterior and a posterior, ( e . g. on the abdomen of
Grasshoppers, — Tab. VII. fig. XXI. C. — and also in Li-
bel lulse, several Pupae, Caterpillars, and perfect Butter-
flies,) which, being surrounded by delicate muscular fibres,
probably, as in the Iris, (§. 398-99.) partly radiated and
partly circular, afford the means of closing or expanding
the opening. According to SpRENGEL,f this structure is

. • • i i • i'*

* KlESER, Anal. d. Pflanzen, s. 154.

f Cornmentarius de Partibus quibus Inscda Spiritus v ducunl . Lips,
181.5. p. 7.

VOL. II.

162'

more complicated in several Water-beetles, one Valve'
being beset with little feathers, thus resembling the bran-
chial structure. Besides these, however, there are also
circular Stigmata, e. g. in the Willow-Caterpillar, (Tab.
VII. fig. XVIII. A.) and the Thorax of the Grasshopper,
(fig. XXL B. X.) where they are peculiarly distinguished
by the presence, within this round opening, of a fine, white
membrane, shaped like an Eyelid, which rises and falls
like a valve during the very powerful respiratory motions
of these animals. The edges of the Stigmata are occa-
sionally, also, guarded by little bristly hairs, (in the Mole-
Cricket, according to Sprengel,) or prominent, protruding
like nipples ; as, for instance, in several aquatic Larvae.
Lastly, the Stigmata are occasionally almost wholly closed
by a perforated cribriform membrane, (as in the Larva of
the Cockchafer, Melolontha vulgaris ,) which has lately
given rise to the erroneous idea that no air penetrates the
air-tubes.*

§. 580. As to the air-tubes (Tracheae), we find them
uniformly arising from Stigmata, (rarely from Gills,) ex-
tending in two principal trunks along the sides of the body,
or radiating in a tuft-like manner from each stigma : they
always, however, ultimately divide into smaller ramifica-
tions, which not uncommonly present bladder-like dilata-
tions, and are ultimately distributed as extremely minute
branches to all the organs of the body, somewhat like the
Arteries in Man. The Tracheae themselves are formed by
two membranes, between which, though nearest to the
innermost of the two,f are placed certain elastic, spirally
convoluted fibres, (Tab. VII. fig. XVIII. B.) which, by
their delicacy and density, give to the air-vessels that beau-
tiful, silvery, lustrous appearance which present such a

* Sec Sprengel’s refutation of this idea of Moldenhawer?s, loc. c\t p. 9.

f Sprengel, /. e. p. 14.

i 63

striking- spectacle in the dissection of Insects. It is inte-
resting, also, to find that the V egetable Kingdom affords
prototypes, not only of the Stigmata, but also of the
Tracheae, viz. the Spiral Vessels. It is certain, however,
that considerable differences have been pointed out between
them, e. g. that the connection of the Spiral Vessels with
the fissure-like openings (of Plants) cannot be discovered,
that they do not ramify in the same manner, &c.;* nay,
it is even possible that the Spiral Vessels may have more
of the character of the Nervous System in Animals. It
may, nevertheless, be asked, if it be not probable that
Respiration is to Plants what the Nervous action is to
Animals, and, consequently, whether the most perfectly
developed animal respiratory System may not be a repeti-
tion of the type of the Spiral Vessels? This at least is
certain, that there is more of similarity than of dissimilarity
between the Tracheae and those Vessels.

§. 581. As to the individual Families of Insects, we
will here first briefly notice the most important differences
that have been discovered, as well in that respect, as with
regard to the changes which the respiratory organs expe-
rience from their metamorphosis. The Gnathaptera, e* g.
the Scolopendrae, breathing by means of Stigmata, approx-
imate to Worms by the great number of those organs.f
The true Aptera, also, have a row of Stigmata at the sides
of thfe body.f In the Neuroptera, where the Tracheae
commonly form vesicular dilatations, the Stigmata are
peculiarly developed in the thoracic region, a fact which,
being common to so many Insects, coincides perfectly with
the circumstance that the moving extremities are attached

* Id. p. 12. 16.

f Tsitzsch ( Commentaiio de Respirations Animalium, p. 26.) found sixty
pairg, or even more.

} Swammerdam Bib. Nat. Tab. I. (of the Louse.)

M 2

1(54

in 'the same region, (§. 148. 149.) In the Larvae of tins'
Order, however, the respiratory organs are formed after an
inferior type. Besides that here, as in all Larvae, the
vesicular dilatations of the Tracheae are wanting, and that,
as in nearly all aquatic and intestinal Larvae, two broad'
tracheal trunks extend from the head to the anus, giving
off’ only small lateral ramifications; there are, also, in the
Larva of the Ephemera six true branchial laminae on each
side of the posterior part of the body.* In the Larvae -of
the Libellulse, on the contrary, there are indeed Gills, but
situated in a dilatation of the Rectum (§. 455.) : these
animals consequently breathe like the Holothuriae, by the
Intestine, and like them swim by forcibly expelling the
respired water from the anus. Besides the Gills, how-
ever, SpRENGELf found, also, from 7 to 9 Stigmata at the'
sides of the body.

§. 582. The respiratory organs of the Diptera, both in
the perfect Insect and the Larva, present much similarity
to those of the preceding division. In the perfect Insect
there are air-bags (dilatations of the Tracheae), and in
addition an air-bag on the Oesophagus, the origin of which
will be noticed hereafter. In the Larvae, on the contrary,
when they live in water, there are either external elon-
gations of the two tracheal trunks of the body, (e. g. in the
Larvae of Gnats,! a long respiratory tube at the anus, by
means of which they suspend themselves at the surface of
the water, and in the Pupa of the same Insect two little
respiratory horns on the head,) or tufts of hair instead of
Gills, and that even without Trachea?, e. g. in the Tipula
plumosa. In Larvae which live within other animals, c. g,
in those of the Oestrus equi, frequently present in great

* Swammerdam, p. 104.

| Comment, de. viis quihus Insect, spiriius ducunt. p. 3.

1 Swammerdam, Tab. XXXI.

165

numbers in the stomach of horses, I find a smooth, oval,
brown plate at the posterior part of the body, the lateral
halves of which present several parallel lines, which appear
like the contracted apertures of Stigmata : when this plate
is removed we find tolerably large Stigmata, from which
the two thick tracheal trunks proceed towards the head,
in Larvee which live in the air, e. g. the Mite, the Larva
of the Musca putris* two little respiratory tubes project
from the second, and again from the last segment of the
body.

§. 583. In the Hymenoptera, the Tracheae and Stigmata
of the perfect Insect are tolerably similar to those of the
preceding divisions : the Larvae, on the contrary, e. g. those
of Bees, are more perfect, and have regular Stigmata at
the sides of each segment of the body. The Hemiptera
again, in their imperfect metamorphosis, by the presence
of elongated respiratory tubes, (e. g. in the Nepa,) accord
more closely with the. Neuroptera, or even their Larvae.
The Orthoptera, also, approximate to the Neuroptera by
their large thoracic Stigmata. It is remarkable that the
respiratory motions of the body are more distinctly percep-
tible in this division than in any other Insects. In the Lo-
custa verrucivora particularly, it is easy to distinguish how
the abdominal rings, which have smaller abdominal scuta be-
tween them inferiorly, are alternately elevated and depressed
exactly like Ribs. If we smear the great thoracic Stigma
with oil, we find that numerous little bubbles of air escape
from it during these motions. The whole is probably con-
nected with the large and elegantly arranged air-sacs of
the posterior part of the body (Tab. VII. fig. XXI.' A. b.),
which are distinguished by the circumstance, that when
free from air and collapsed, they appear like broad and
usually red-coloured stripes. Lastly, I may mention, that
* Swammerdam, Tab. XLIII. s. 276.

1GG

in dissecting these Insects, particularly when they had been
destroyed by obstructing the Stigmata, I always found the
dilatation of the (Esophagus and the Crop thereby formed,
filled with air ; so that, consequently, here, as well as in
many other Insects, Respiration can be performed in the
Intestine, though chiefly in its anterior part.

§. 584. As regards the Coleoptera, we again find the
usual vesicular dilatations of the Tracheae in the perfect
Insect. In the Larva, the ramifications are simply abores-
cent, proceeding in tufts from the Stigmata. The Stigmata
are placed at both sides of the body, as is also the case in
Caterpillars, (the Larvse of the Lepidoptera,) in which the
respiratory organs have been most frequently examined.
In them there are two long tracheal trunks at the sides of
the body, (as was already the case in the Larvse of the
Neuroptera and Diptera,) but connected with each Stigma,
from which a radiated tuft always proceeds to the neigh-
bouring parts. (Tab. VII. fig. XI. m. 1. k.) In the
Butterfly, the vesicular dilatations of the Tracheae are par- T
ticularly distinct, usually forming large oval sacs and being
placed in the posterior part of the body, in the direction
from below upwards. Besides these, there are also little

luntr-like cellular bodies on the Tracheae and air-sacs. As
©

Meckel* has observed, the air-sacs appear in the Pupa
soon after its involution ; but I believe that the cause
of this appearance must be looked for chiefly in the closure
of the Stigmata, particularly the posterior ones.fi The air
of the Tracheae appears to be thereby much confined, and

* Translation of Cuvier’s Comp. Anat. vol. iv. p. “286.

f Dk Geer ( MemoiressurlesInsect.es , vol. i. p. 41) remarked, that in
the Pupa of a Sphinx the 2 or 3 posterior Stigmata were closed, whilst little
bladders of air passed alternately in and out of the anterior ones under
water, lie considered this as In and Ex-piration, but probably incorrectly,
inasmuch as the expired air was taken in again.

1 67

its quantity probably increased* by the disengagement of an
additional quantity during the developement of the organi-
zation ; whence, probably, the air thus accumulated may
mechanically produce the distension of the tracheae into
air-sacs, and whence, also, we can understand why these
vesicles should occur chiefly in the posterior part of the
body. Nay, it may even be questioned if the air-sac on
the (Esophagus of Butterflies and Gnats may not be pro-
duced in the same manner, inasmuch as the observations on
Crickets, before mentioned, as. well as the air-bladders of
this sac itself, prove that the (Esophagus serves for the
reception of air, — for a kind of respiration.

§. 585. The organs of respiratory motion, by means of
which the supply of air is renewed, present many points of
uncertainty. On the one hand, where large Stigmata are
placed opposite to each other, and connected by Tracheae,
it is easy to see that the alternate opening and shutting
of their valves may produce a current capable of renewing
the supply of air.f It is conceivable, also, how in the
Orthoptera, Lepidoptera, and others, the expansion and
contraction of the body, and the elasticity of the air-sacs
contained in it, may cause the ingress and egress of air.
It is less obvious, however, how the same effect is produced
in Caterpillars and the Larvae of Beetles, where a current
of air cannot very easily arise from the opposite position
of the Stigmata on account of the minute ramification of
the Tracheae; and consequently we must look for some
peculiar mechanism, unless we are disposed to admit the
stagnation of the air in its vessels. Hence it has been con-
jectured that the dilatation and contraction of the dorsal
vessel, hereafter to be described, contributed to this pur-

* On opening under water the Pupa (several days old) of the Moth of
the Euphrobia, I observed the escape of air with some force.

f NlTZsCH, Comment, dr. Respirdt. p. .‘19.

108

pose :* this, however, appears to be scarcely possible, and
it might be asked, on the contrary, if the motions of the
body itself, the sliding of its segments upon each other,
&c. are not the means of keeping up the constant ingress
and egress of air ? This, however, is not the place for any
more extended investigation of the point.f

B. Respiration of Animals with Spinal Marrow

and Brain.

Section I. Respiratory Organs of Fishes.

§. 586. As we very commonly find in the Animal
Kingdom that some species in a given Class or Order are
its proper representatives, whilst others are to be con-
sidered as intermediate links of connection with superior
or inferior formations, so also is it in Fishes ; among which
the Abdominales appear most decidedly to present in their
structure every thing essential to the idea of a Fish ; whilst,
on the contrary, Rays and Sharks, and Myxines and Lam-
preys, leave us almost in doubt whether we should not
rather arrange the former with Amphibia, and the latter

* Reimarus, Ueber das Athmen. in Reil’s Archiv. b. xi. h. 2.

f Under certain circumstances Bees emit a voice, consisting in a shrill
sound, independent of the motions of the wings, and which appears to be in
some manner connected with the existence of a current of air through the
respiratory Trachere. At least it was observed, that when the animal was
irritated, and immersed in water, the surface, where it was in contact with
the orifice of the stigma at the root of the wing, evidently vibrated at the
moment the sound wlw produced. (Hunter, Phil Traits. 1792, p. 182.) —
Translator.

with Worms. It is in that Order, also, that we find most
definitely expressed the type of formation of the Respiratory
Organs peculiar to the Class ; consequently we shall first
describe those Organs as they appear in it, and then notice
the variations which take place in others.

§. 587. In the Abdominaies, and also in most Fishes,
there are two kinds of respiratory organs ; of which one
only, like the lungs of Man, performs alternate expiration
and inspiration, whilst the second, on the contrary, appears
to act merely as a means of excretion. The former, con-
sequently, is the true and uniformly existing respiratory
apparatus, whilst the latter is found in the greater number
only. The organs of the first kind, as the respiratory in-
struments of the aquatic animals, which, in the superior
division of the Animal Kingdom, present repetitions of the
lowest gradations of animal organization, are, as was usual
in the Mollusca, Gills ; nay, these gills are defended by
moveable valves (opercula) precisely in the same manner as
those of the Bivalves. The second kind of respiratory
' apparatus consists in a membranous sac provided with nume-
rous vessels, and comparable to the air-sac of several
Medusse, (§. 560.) the swim-bladder as it is called. The
principal element of the air contained in it is usually Azote,
(nearly pure in the Carp Genus,) rarely mixed with Car-
bonic Acid or Hydrogen Gas, and sometimes also contain-
ing a proportion of Oxygen Gas, varying even in the same
species, but often very considerable, and apparently greater
in proportion to the depth at which the animal lives.

§. 588. We will first consider these organs more pre-
cisely in some Abdominaies, e. g. the Carp and Pike. As
to the Gills, they are attached to the external convex sur-
face of the four branchial arches, or thoracic ribs, already
described, (§. 164, 165.) forming on each of them, (Tab.
IX. fig. XIV. i. i. i. j.) nearly as in the viviparous Snail,

(§. 576.) a double pecten of separate dark-red brancliial
fibres, which float loose in the water. The water enters at
the mouth, passes through five fissures on each side of the
fauces, and escapes through the branchial openings placed at
each side of the head, and covered by the moveable Opercu-
lum (§. 178. Tab. VIII. fig. XII. k.) as well as the branchial
membrane. (§. 179. Tab. IX. fig. XVIII. c.) The fissures,
which are guarded internally against the entrance of food
by means of little papillae or small branchial teeth, have
each, in fact, the same character as the Rima Glottidis in
Man, in so far as they convey the respirable medium to the
respiratory organs. The opening of these fissures is effected
partly by peculiar muscles of the thoracic ribs, partly by
those of the lingual bone, (§. 179.) of the pharyngeal
maxillae, (§. 170.) and of the belt of bones; (§.167.)
muscles which also contribute to form the fleshy septum
by which this entire respiratory apparatus is closed poste-
riorly. Hence we might be led to compare this septum to
the human Diaphragm, were it not that the heart is placed
without, and behind or below it, (Tab. VIII. fig. XI. 1.)
being still separated from the abdomen by a tendinous
membrane. The proper respiratory motion is here an
elevation and depression of the branchial arches, corres-.
ponding pretty closely to the motions of the true ribs in
Man; with this difference, that this respiratory apparatus
is attached to the basis of the Cranium, and that the true
respiratory organ, together with the heart, is not situated
within the thorax, but is attached to the ribs externally in
the form of branchial fibres, which may be considered as
everted and elongated cells of lungs. The branchial mem-
brane, the folds of which, as well as the operculum itself,
are moved by peculiar muscles attached to the lingual
bone, is attached internally to the operculum, and, inas-
much as it alternately opens and closes the branchial aper-

171

tare, is circumstanced nearly like the membranous cloak,
placed under the shell of Bivalves. (§. 503.)

§. 589. The swim-bladder in the Pike consists of an
elongated sac placed within the abdominal cavity imme-
diately beneath the vertebral column and the kidnies, and
connected to the spine by several symmetrical tendinous
ligaments. When opened, it distinctly presents, in addi-
tion to a thin covering which it receives from the perito-
neum anteriorly, two membranes, viz. an exterior one,
tendinous and very strong, and an internal, vascular and
more delicate. There are some dark spots on the posterior
or upper surface, and the vessels are more numerous ante-
riorly than posteriorly. The excretory duct, proceeding
from the anterior part in the form of a tolerably wide but
short canal, enters the pharynx; not, however, like the
human trachea, at its anterior, but, on account of the situ-
ation of the bladder, at its posterior part. This air-passage
is not surrounded by the tendinous membrane, being merely
embraced at its origin by a projecting fold belonging to it.
It is scarcely possible to detect any traces of muscular struc-
ture in the parietes of the bladder in this Fish ; and, conse-
quently, from its length, from its firm attachment by
ligaments to the spine and ribs, as well as the width and
shortness of its excretory canal, the air it contains is pro-
bably evacuated only by the compression of the organ by
the lateral muscles of the body.

§. 590. In the Genus Cyprinus, on the contrary, the
swim-bladder is less closely connected with the vertebral
column, and is divided into two parts ; of which the poste-
rior and longest is distinguished by its greater vascularity,
and by giving origin to the excretory canal. This posterior
division is connected with the anterior by a short and rather
rather narrow passage, and is covered by a thicker layer of
fibres, which appear to me to be muscular. The excre-

1 12

fory canal is here very long and narrow. In the superior
hall of the organ the fibrous stratum is wanting, so that it
appears like a hernia of the inner membrane taking place
between the fibres at the upper end of the other portion ;
the inner membrane, however, is lined with a delicate vas-
cular mucous rete, and covered externally by a firm, ten-
dinous, white stratum. It does not appear to have any
' peculiar action, but merely to repel by the elasticity of its
external membrane the air forced into it by the contrac-
tion of the lower half.

§.591. Having in these examples given a general idea
of the respiratory organs of Fishes, we shall next proceed
to consider the most important of the variations from this
form, in doing which we shall have an opportunity of observ-
ing more completely the character of these organs. In this
respect, the variation which the respiratory organ undergoes
in the Chondropterygii is remarkable; for, as in several
Mollusca, e. g. the Slug, but more particularly in many
Articulata, (especially Worms and Insects,) the respiratory
organ is concealed within the body, and the respired
medium penetrates by one or more openings, generally
placed at the sides (stigmata), so, also, is it in these Fishes,
and especially in the Gastrobranchi and Lampreys, which
approach so closely to Worms. In the former, accord-
to Homjs,* the branchial openings are placed on each side,
at the commencement of the (Esophagus, being six pairs,
and appearing not as fissures, but as small round foramina.
The water is conveyed to these openings partly by the
mouth, partly by a very singular external opening of the
(Esophagus, probably exclusively peculiar to these animals,
and partly by the spouting tube already noticed in the
Fresh-water Lamprey, (§. 348.) although this as well as
the abdominal opening of the (Esophagus appear to me

!* Philos. Trans. 1 - 1

175

dtore calculated for expelling- than receiving- it. The water
flows from these openings by short canals to six small round
respiratory sacs on each side, containing branchial projec-
tions ; and from these passes by the same number of little
eanals into a common tube near the gills on each side,
terminating- by two foramina close to the thoracic orifice
of the (Esophagus.

§. 592. In an animal, which, according to Home, forms
a transition from the Gastrobranchi to the Lampreys, there
are also seven lateral openings in the (Esophagus on
each side, leading to tubes which expand in the 'middle of
their course into respiratory bladders, and terminate exter-
nally by seven branchial foramina (stigmata). In the Lam-
prey (Petromyzon marinus) , the principal difference in
structure is, that the openings of the branchial sacs do not
arise from the (Esophagus. A membranous canal (a
trachea as it were) ascends in front of the (Esophagus, in
which we observe two lateral rows of seven foramina leading
to the branchial sacs. These elongated sacs, provided
internally with several branchial laminae, open externally
by seven foramina, which are surrounded by several elastic
cartilaginous arches, that here supply the place of the bran-
chial arches. (Tab. VIII. fig. IV. 15, 17, 18.) Here, also,
the water appears usually to enter the trachea by the mouth,
Und to pass out again by the branchial openings. The
spouting tube, which Home has incorrectly asserted not tor
penetrate internally, opens merely into the commencement
of the (Esophagus, and consequently cannot possibly con-
vey water to the gills when the mouth is fixed by suction ;
(§. 462.) partly because it is too small for the purpose, and
partly because there is nothing to contradict the suppo-
sition that *the water may alternately flow in and out of
the branchial foramina, as so commonly happens in other

tmimal.s, As to the swim-bladder, it appeal's to be here
altogether wanting.

§. 593. In Rays and Sharks, more as in the first in-
stances, and as in Osseous Fishes in general, there are five
internal branchial fissures, which receive the water con-
veyed by the mouth, or by the temporal holes, and force it
out, not through a large opening covered by an operculum,
but, nearly as in the Lampreys, by five short* fissures
placed one behind the other. Here, as in the preceding
cases, the thorax, as already (§. 164.) noticed, is situated
not at the base of the head, but farther backwards. The
swim-bladder is wholly wanting.

§. 594. In the Branchiostegi, as well as in the Jugulares,
Thoracici, and Apodes, the gills are pretty generally
circumstanced as in the instances already given in the
Abdominales, although there is no deficiency of individual
variations. In the Eel, for instance, the external opening
of the cavity that contains the gills is merely a round
aperture from one-third to one-fourth of an inch across, and
situated under the Operculum; in the Hippocampus,
According to Cuvier, the gills form eight tufts attached to
■cartilaginous laminae ; so also, according to Tiedemann,!
in the Syngnathi, there is merely a grape-shaped gill, con-
tained in a branchial cavity opening externally merely by a
small Opening. In the Silurus anguillaris , according to
Geoffroy, in addition to the four gills there are four

* According to an interesting observation of Rudolph:, (Oken’s Isis, b.

h. 7, s. 109.) it is probable that Rays and Sharks have originally two gills
projecting from these branchial fissures, which are subsequently retracted in-
ternally. Hence, in this period, the floating gills of Osseous Fishes are
found also in these superior species, differing only in not being covered by
Opercula.

| Meckel’s Archiv.f Physiol, b. ii. h, 1. s. 112.

175

hollow arborescent laminae, on which the branchial arteries
not only hlmify, but also effuse blood into them. A more
complete examination of individual Genera will present
many additional varieties.*

§. 595. There are many remarkable physiological
varieties to be noticed in the structure of the swim-bladder.
Besides the Chondropterygii, it is not unfrequently want-
ing- in other instances, e. g. in the Genera Lophius, Pleuro-
nectes, and in the Mackerel (Scomber scombrus), &c*
Secondly, even when it exists, the air-duct is occasionally
absent, e.g. in the S risen a umbra, Cobitis barbatula (Loach),
and fossilis , in the Burbot (Gadus lota), and others, men-
tioned by De la Roche. •f On the contrary, the duct,
according to Cuvier, is double in the Cod ; and in the
Sturgeon opens into the stomach instead of the oesophagus.
As to the form and internal structure of the organ, we find
the following principal variations from the description given
in the Carp and Pike, which is common to many other
species: it is occasionally composed of two air-sacs placed
close to each other, like the lungs of superior animals; such
is the case in the Loach and Cobitis fossilis , where the two
minute bladders are surrounded in a remarkable manner
by bony cases proceeding from the anterior extremity of
the vertebral column and also, according to Cuvier, in

* The parietes of the organs above described in the Silnrus anguillaris are
state/i by Cuvier to possess an afterial character, and present on their in-
ternal surface numerous villosities, through which exude the contents of the
minutely ramified branchial arteries. The trunks themselves open into the
roots of the Aorta at the point where they arise from the branchiae. Ac*
cording to him, besides their office as respiratory organs, they are also t<r
be considered in the light of hearts seated at the origin of the principal
arteries of the body, accelerating the current of blood through them, and
thereby increasing the force and activity of the animal. — Translator.

f See his Essay on the Swim-bladder, in the Amales du Museum.

| According to CuvrER ( Memoires du Museum d' Hist. Nat, vol. i, p. 320)

flie Biehir, (Polypterus niloticus , Geoff.) where one sac
is small, the other very large, and both open together into
the (Esophagus.

§. 596. The Swim-bladder of the Scisena umbra is
distinguished, according to CuviErt,* by having a great
number of blind, and sometimes arborescent, appendices
Or diverticula attached to its edges, and also by the pre-
sence of some almost glandular bodies, -j- as well upon its
circumference as its internal surface. The internal cellular
structure of the Swim-bladder in several Fishes is likewise
physiologically important, in so far as it forms a transition
to the form of Lungs of the superior Classes. Such is the
case, according to several observers, in the Sword-fish,
(Xiphias gladius,) in some species of Silurus, Tetrodon,
and Diodon. Lastly, the Swim-bladder of the Sturgeon
dnd Beluga (Accipenser sturio and huso), is distinguished
for its size, and for being the material that furnishes
Isinglass4

§. 597. It remains to say a few words on the character
of this part, that of the Gills being already sufficiently
clear as the proper and most essential organ of respiration.
From the intervention of teleological views, the Swim-
bladder has either been considered exclusively as an acces-
sory agent in swimming, or as a true Lung admitting and
returning the external air. That however serviceable it
may be in the former respect, it is yet by no means indis-

there are similar bony coverings to the Swim-bladder in the Ophidium
imberbe.

* Loc. cit. p. 18.

•f- De la Roche (/. c. p. 165.) found these internal red bodies in the
Swim-bladder whenever the air-duct was wanting: according to Cuvier,
there are similar organs, probably for the secretion of air, in Fishes which
possess such ducts, e. y. in the Muranae.

| See Fischer Ueber d. Schwimmblasc der FLschc. I.cipz. 1795.

ITT

pensable, is proved by those Fishes which swim perfectly,
well without it. That its office is not of the second kind
is established by the numerous instances in which the
air-canal is wanting, and by the permanent continuance of
many Fishes at extraordinary depths of the sea, though in
them the proportion of Oxygen Gas in the bladder is greater
than in those which approach nearer to the surface, nay,
in which the alteration in the pressure of the column of
water has such a powerful effect, that, according to Biot,
when suddenly taken from these depths, the rapid expan-
sion of the contents of the bladder is so great as to burst
it.# Hence it is most probable that the swim-bladder is
employed in performing a part of the expiratory fnnctions
of the lungs of the superior Classes, not only separating
excrementitious Azote and the superabundant quantity of
Oxygen from the blood, but also actually evacuating them
in those cases where there is an air-duct.f

§. 598. We might here quit the respiratory organ of
Fishes, were it not necessary to notice some other struc-
tures, which in that Class appear occasionally to have some,

* Configliachi on the Analysis of Air from the Swim-bladder of
Fishes, in Schweigger’s Journal f Chemie ; and Biot’s Essay on the same
subject in Gilbert’s Annalen. 1807, No. 6.

t The communication of the Swim-bladder in certain Fishes with the
internal ear tends to confirm, instead of contradicting, the character assigned
to^tlittt organ as an imitation or rudiment of the lungs of the superior animals.

here the Eustachian tube exists, it forms in the same manner a commu-
nication between the cavity of the ear and the respiratory organs. On the
other hand, the lungs in the Proteus form merely two membranous sacs
without any cells, whilst in certain Serpents the structure is still farther
simplified by the exclusive developement of one lung, the other remaining
permanently in a rudimentary state. In the Proteus, again, the closed state
of the swim -bladder in other Fishes is very nearly imitated, the bronchi into
which the Trachea divides before it enters the lungs being so small that the
action of alcohol is sufficient to render them totally impervious to the pas-
sage of air. (Weber, Do Aure el Auditu, p. 89.) — Translator.

VOL. II. N

178

and sometimes a very considerable, share in the respiratory
process. Of this nature is the Intestinal Canal ; which

appears in all Fishes, except the Lampreys, to be closely
connected at its anterior extremity with the respiratory
organ, inasmuch as it admits water, and has the gills placed
on each side of it; of which, too, it has been proved, as
regards the Cobitis Joss ilis, by the interesting experiments
of Erman,* that it is in itself a respiratory organ, and even
that this respiration is indispensable to the support of life.
In some experiments of my own I had particularly occa-
sion to remark the thinness and vascularity of the intestine
which runs almost direct from the stomach to the anus,
and differs materially in its structure from the stomach,
and from the generally thick-coated intestine of other
Fishes. I found it also almost completely empty of food ;
and, as is well known, these animals may be long kept in
glasses with sand and water, without any other nourish-
ment. It is needless to point out how closely this intestinal
respiration resembles that of the Holotliurise, (§. 561.) Li-
bellulse, and Larvae of the CEstrus. (§. 580, 581.) It is
probable, also, that a similar kind of respiration, as Meckel
suspects, may take place in other Fishes; though it is
scarcely possible in those instances in which the membranes
of the intestine are unusually thick, or even cartilaginous,
as in the Pike.

§. 599. Another organ which has appeared to me to
contribute in some Fishes to the respiratory process con-
sists in the Peritoneum, Mesentery, and external, membrane
of the Intestine. In the Chondropterygii, as already
observed, (§. 472.) there is a fissure on each side of the
anus, by means of which the water can enter the abdomen,
and come in contact with its included organs. These
remarkable openings may probably derive their primary
* See, his Essay in Gilbert's Annalen, l>. xxx.

179

importance from tlie sexual organs, as we shall find when
we come to consider those parts; but may still, also, in
Rays and Sharks, have relation to the respiratory process,
from the frequency of the existence of an intimate connec-
tion between the sexual and respiratory organs. This
form of Respiration reminds us, likewise, of a similar
one in the earlier formations ; where, as, for instance, in
the Medusae, the respiratory sacs lie immediately below the
stomach : or, as in the Aphrodite, the cceca are bathed in
the surrounding water.

Section II. Respiratory and Vocal Organs of the

Amphibia.

§. 600. As in this Class there is a gradual developement
of the animal formation from an aqueous to an aerial being,
so also is the aqueous gradually converted into aerial respi-
ration ; and the respiratory organ represents that form
which was proper to those of the preceding Classes, in
which there was respiration, or even expiration, of air. Of
that kind are the air or swim bladders of Zoophytes, the
respiratory cavities of many Snails, the tracheae and air-
ves/cles of Insects, and the swim-bladder of Fishes. But,
as in those Fishes where the true respiratory, i. e. bran
chial, apparatus is most completely separated from the
intestine, ( e . g. in the Lamprey, §. 592.) it is placed
below or in front of the (Esophagus ; so, also, is it as regards
the apparatus for respiring air in Amphibia, Birds, and
Mammalia, where it receives the name of Lungs, whilst,
on the contrary, the intestine appears scarcely to take any
part in the respiratory process. By the name of lungs are

n 2

180

distinguished cellular sacs for the reception of air, more or
less closely compacted, communicating with the mouth or
fauces by an air-tube (trachea), more or less long, some-
times merely membranous, at others provided with cartila-
ginous rings, and thus reminding us of the tracheae of
Insects. In this and the following Classes it is important
not only as a part of the respiratory mechanism, but also,
by the addition of peculiar organs of motion, and in con-
nection with modifications of the mouth, nose, tongue, and
lips, as a vocal organ.

§. 601. Organs for the formation of true Voice are alto-
gether wanting in the four preceding Classes, though many
animals belonging to them have the power of producing
some sound or single tones, but not so much by peculiar
vocal organs as by other parts, which however generally
belong more or less immediately to the respiratory appa-
ratus. Snails, for instance, occasionally emit a certain sound
by suddenly opening or shutting the orifice leading to the
respiratory cavity; so, also, many , Insects* produce sounds
for the most part by means of the wings, which is physiolo-
gically not unimportant, when we consider with how much
propriety the wings of Insects have been already viewed
as gills dried up. (§. 150.) Lastly, there are many Fishes
which, in a manner as yet but imperfectly understood, emit
a murmuring noise, e. g. the Cobitis fossilis and the Trout.
In the former the distension of the Intestine with air is
probably the principal cause of this sound ; and, conse-
quently, it is comparable rather to the rumbling in the

* E. g. the Grylli, by rubbing the upper dry wings against each other ;
Gnats and Flies by the friction of the roots of the wings in their articular
cavities, the Poisers (Halteres), according to Oken, ( Zoologie , b. i. s. 466.)
not contributing. The latter species consequently produce a buzzing whilst
flying only, as we observe also in Beetles, from the motion of the wings and
elytra; whilst in the former it is heard when they are at rest.

181

intestinal canal of the superior animals than to a pulmonary
Voice.

(A.) Batrachia.

§. 602. As regards its respiratory organism, this first
Order approximates in a very remarkable manner to the
preceding ; partly, inasmuch as the larvae of the animals it
contains breathe precisely as Fishes, by means of gills,
and partly because there are a few larva-like species in which
the gills appear to be permanent during the whole term of
existence. We shall first proceed to examine the latter,
including the Genera Proteus and Siren, and the Acholotl,
(Gyrinus mexicanus.)* In all of them we find branchial
arches, which, precisely similar as in Fishes, are connected
with the lingual bone, and fixed immediately behind the
head. In the Proteus there are three, and in the other
species four, sjich pairs, to which the gills are attached, the
water entering through the mouth, and escaping through
the fissures between the arches, exactly as in Fishes. The
gills themselves hang from the upper part of the branchial
arches in the form of feathered twigs, and project consi-
derably out of the branchial apertures. In the Proteus
which lives in the subterraneous lakes of Carniola, they are
dually of a pale red colour, but I found that on exposure
to a brighter light they soon became darker. Besides the
branchne there are also pulmonary sacs, which coincide very
closely with the swim-bladder of Fishes, and, according to
Hunter,-}- extend almost to the anus : they are mem-

* Which, however, may yet be the larva of a Triton. See Cuvier,
Recherchcs Anatomiques sur les Reptiles regardes encore comme douteux par let
Naturalistes. Paris, 1807, 4-to.

f Philosoph. Trans. 1766, p. .307.

182

bran ous, and in the Siren particularly long, reaching to the?
extremity of the abdomen. The excretory passages (bronchi)
ot these lungs are also membranous ; and it is only in the
Siren and Acholotl that they present the rudiment of a
cartilaginous larynx where they open near the tongue. In
the Proteus, according to Schreibers,* instead of a larynx
-there is a membranous cavity, which opens by means of a
small fissure into the pharynx, and is continued posteriorly
into two long membranous canals, which ultimately termi-
nate in the pulmonary vesicles.f

§. 6 03. As to Frogs and Salamanders themselves, we
find in their larvae precisely the same structure of the
respiratory organs as in the preceding species. Floating
gills* originally project at each side of the head, become
subsequently gradually smaller, and as soon as the animal
begins to take in bubbles of air by the mouth, leave merely
an opening at the left side of the head, (a branchial open-
ing like that of the Cartilaginous Fishes, except that it is
here on one side only,) through which the water escapes,
until at length this also disappears, and the animal is limited
to pulmonary or aerial respiration. It is remarkable, how-
ever, that even subsequently, when the perfect animal
respires by lungs alone, the laryngeal region and the lin-

* Philosoph. Trans. 1801, p. 255.

f In the Proteus and Acholotl the branchiae form long and delicately
fimbriated plumes, or tufts, the roots of which are attached to a correspond-
ing number of cartilaginous arches like those of Fishes. In the Siren
lacertina the tufts are shorter, less divided, and fixed to the branchial arches
by a fleshy pedicle. In the Tadpole of Frogs they are more numerous, but
shorter, less complicated, and arranged along the branchial arches, which
are four in number, and merely membranous. (Cuvier, Comp. Anat. iv.
349.) — Translator.

1 Probably a repetition of the originally floating gills of Sharks. See
Pc mark to §. 593.

183

gual bone are the agents of the proper respiratory mecha-
nism. This part of the body consequently not only acts in
the larva as a true thorax like that of Fishes, (§. 164.)
but even subsequently assumes the function of a thorax :
hence, too, we are enabled to understand why a thorax
formed by true ribs is wanting in this species of Amphibia;
(§. 182.) because their thoracic ribs originally forming-
branchial arches, as in Fishes, none others can be developed
on the lower vertebrae, and when those arches disappear,
there can of course be no thoracic ribs remaining.

§. 604. As to the lungs themselves, their membranous,
vesicular, and loosely cellular structure, still presents a cer-
tain similarity to swim-bladders : (Tab. XIII. fig. VI. b. c.)
they form two sacs placed at the sides of the trunk, extend-
ing low down into the cavity of the abdomen, which is not
distinct from that of the thorax, the right being some-
what larger than the left, and both, when empty, con-
tracting into a very small space. In the Pipa the parietes
of the lungs are more substantial; they have numerous
septa internally ; and, as regards their external form, are
broader and shorter in the male, in the female longer,
but narrow.* There are scarcely any bronchi in Frogs
and Salamanders, the lungs appearing to be attached to
the larynx almost immediately, and without any trace of
a true trachea. The larynx, on the contrary, is of consi-
derable width in the Frog, opening into the mouth by a
rima glottidis without any epiglottis, though the tongue
may in some degree serve the purpose. (§. 477.) It is
provided also with two strong vocal ligaments on each
side, ( Fab. XIII. fig. VI. d.) by means of which, as well
as from the mobility ol the rima, it forms a very powerful,
and the first pulmonary, vocal organ. The following is
the mechanism of respiration, as described particularly by

BitEYER, Observed. Anal, circa fabricam Ranee Pipac, p. 15.

184

■Townson,* though before noticed by Swammerdam and
Malpighi. When the broad lingual bone (§. 476. Tab.
XIII. fig. VI. a.) which forms the floor of the mouth is
drawn down from the palate by its muscles, the air of the
mouth is rarefied, and an additional quantity enters by the
nasal apertures, f which admit of being closed by valves.
The lingual bone is then raised, the nasal, apertures are
closed, and the air is forced, or rather swallowed, through
the rima glottidis into the pulmonary sacs, and can also
fill the laryngeal pouches (§. 478.) which open into the
mouth. We thus see why the lungs of these animals
may still be distended when the cavity of the trunk is laid
open ; which appeared strange to many physiologists, who
looked only to the respiratory mechanism in Man. We
find also a confirmation of what has been already men-
tioned, viz. that the respiratory motions of these animals,
like those of Fishes, are performed by the pharynx. The
contraction of the lungs is produced partly by the pressure
of the abdominal muscles, and partly by the peculiar mus-
cular power of their own parietes.

§. 605. In the Pipa, the air-tubes, as well as the
Larynx, differ considerably from those of Frogs and Sala-
manders. There is indeed no proper Trachea, but the
Bronchi are longer, particularly in females, (in which the
Lungs are on that account smaller,) and are even furnished
with minute cartilaginous rings, which are otherwise want-
ing in this Order. As to the character of these cartilagi-
nous rings of the air-tubes, which here for the first time
present themselves, they may be considered partly as repe-

* Tracts and Observations in Natural History , Sfc. London, 1799.

f The motion of the nasal apertures, nay, even of the glottis itself,
is a repetition of the opening and shutting of the stigmata of the lower
animals,

185

fcitions of the cartilaginous branchial arches of Fishes, which
become at once smaller and more numerous, and partly as
repetitions of the circular fibres of the Tracheae of Insects.
The latter analogy is probably the most correct, for, if the
first actually existed, the branchial arches in the Amphibia
that undergo metamorphosis should be converted into the
tracheal rings, which is not the case.*

(B.) Chelonia.

§. 606. The respiratory organs of these animals have
in general been but little investigated, and are by no mean?
perfectly known, though they approach closely to those of
the preceding Order, the moveable Thorax being wanting

* Rudolpiii ( Obs . Anat. circa fabric. Ranai pipcc. Berol. 1811. 4to.)
has given a description of the organ which, in that animal, forms at once
Trachea and Larynx. It is compressed from above downwards: in the
male is about 10 lines in length, broad at the basis, in the middle, 2
lines thick, and composed of two laminse of bone ; in the female it is smaller,
and is cartilaginous, with the exception of two longitudinal ridges of bone.
The two Bronchi arise immediately from this organ without the interposition
of a Trachea, being very short in the male, but, on the contrary, very long
in the female.

4s regards the character or signification of the rings of the Trachea in
gerieral, Geoffhoy St. Hilaire considers them as constituting a repetition
of the Sternum with its Ribs. However fanciful such an idea may appear,
RuDOLPHi ( Physiologic , b. i. s. 390.) has recorded a variety of formation
observed by him in the Trachea of a young Lion, that appears to counte-
nance it. The first ring of the Trachea was regularly formed, but was
pushed up under the Cricoid Cartilage, its extremities overlapping each other
posteriorly. The six following Rings werq divided in front by the interpo-
sition of a long, narrow slip, common to all of them, and having the same
relation to them as a Sternum to its Ribs. Consequently, instead of six
perfect Rings, there were 13 separate pieces, viz. 12 lateral ones, and a
middle one common to all. — Translator.

also in this case. In the Lungs of the Mud-Tortoise, I
find two very large sacs of cellular structure, more dense
above than below, placed under the Spine, and extending
considerably downwards. The Bronchi in some species,
and particularly in the Land-Tortoise,*' are of very consi-
derable length: in the Mud-Tortoise, on the contrary, they
are but short.f The Bronchi, as well as the Trachea, have
usually circular cartilaginous rings around them, — the length
of the Trachea being in an inverse ratio to that of the
Bronchi, and, consequently, very inconsiderable in the
Land-Tortoise : in the Hawk’s-bill Turtle (T. imbricata J,
on the contrary, it has 38 complete cartilaginous rings,
and each Bronchus only 27. It is remarkable that in some
species the branches of the air-tubes extend very far into
the Lungs, communicating with the lobes only by detached
large apertures. The Larynx is without Vocal Ligaments,
and, consequently, is incapable of producing sounds. The
respiratory mechanism appears to depend partly, as in
Frogs, on the parts about the throat, and partly, (particu-
larly according to the researches of Townson,) on muscles
of the trunk analogous to the oblique abdominal muscles.
That the action of the latter is here the most important,
appears probable to me, from the absence of branchial
arches in the young animal. (See §. 603. 604.)

* According to Paksons, (Philosojih. Trans. 1766. p 213.) the Bronchi
were G inches long in a large Land-Tortoise from Coromandel. He gives,
also, a representation from Blasios of the air-passages of a Land-Tortoise,
where the Bronchi each bend outwards so as to form a loop.

-j- So, also, according to Townson, (/. c. p. 99,) in the T, orbicularis.

1ST

(C.) Ophidia.

§. 607. As the double pulmonary vesicles of Frogs and
Salamanders represented the double Swim-bladder of the
Polypterus niloticus and other Fishes, so, on the other hand,
we may compare the single bag-like pulmonary sac of
Serpents, which extends beneath the Spine a considerable
distance towards the caudal extremity, with the single bag-
like Swim-bladder attached to the Spine in many other
Fishes, e. g. the Pike or Burbot. In most Serpents, (pro-
bably in all those where the tongue can be protruded to a
considerably extent,) the Trachea commences almost im-
mediately below the internal nasal openings, by a rounded
projection above the sheath of the Tongue, with a narrow
longitudinal fissure in it, serving as Rima Glottidis and
entrance to the Trachea. The latter is from 2 to 4 times
as long as the head, and like that of Tortoises, is formed by
delicate cartilaginous rings, of which the upper alone are
perfectly circular, a few of the most completely developed
forming a kind of Larynx : the inferior rings, on the con-
trary, like the cartilages of the human Trachea> surround
only its anterior part. (Tab. XIII. fig. VII. a.) On the
posterior side is a fine vascular membrane, which, gradually
expanding, is extended iijto the right pulmonary sac, in
which the Trachea loses itself by a pointed termination.
The very imperfect Larynx has no Vocal Ligaments, and,
consequently, there is no Voice, but merely Hissing*

* In a species of Water Serpent, Hydrus bicolor, Rudolphi ( Physiologic ,
i. 362.) has described a peculiar provision, by means of which the animal is
enabled to breathe without interruption, when scarcely more than the ante-
rior extremity of the head appears above the surface of the water. It eon-

188

§. 608. Before tl le termination of this Trachea, I hud
both in the Coluber natrix and thuringicus , a small blind
depression, which, as was first remarked by Nitzsch,* is
to be considered as a rudiment of the left Lung. The
right, and, in this case, sole pulmonary sac is placed im-
mediately below the Spine, extends posteriorly as far as
the region of the Kidnies, and in the Coluber natrix is
from 5 to 7 inches long, and from ^ to f of an inch broad.
Its parietes are thickest at the point where the rings of the
Trachea cease ; it is covered externally by a fibrous layer,
and lined internally by a fine lattice-like net-work of
vessels. (Tab. XIII. fig. VII. b.) More posteriorly the
parietes become gradually thinner, and at last are merely
membranous, giving to the whole organ still more of the
appearance of a Swim-bladder. In the Slow- Worm
( Anguis fragilis J, there are two Lungs, nearly as in the
Salamander, though the left is still considerably smaller
than the right.f The respiratory motion here, as in the
other Amphibia, is unassisted by a Diaphragm, and is
effected by the Ribs and abdominal muscles.

sists in the ascent of the Trachea to the anterior angle or symphisis of the
lower jaw, the opening of the Glottis being scarcely more than a line distant
from the point of the tongue — Translator.

* Comment, de Respirat ■ Animal, p. 13.

f It is extremely remarkable that, even in Snails, the respiratory organs
are chiefly developed on the right side ; that this is again the case in Amphi-
bia ; and is observed, also, in Man, (See Soemmering vom Bane d. mensch.
Kocrp. b. v. th. 2. s. 14.); particularly when we consider the predominance
of the power of the extremities of the right side, (for, as is stated in the
Jena Literary Gazette, June, 1817. p. 452, even Spiders employ the right
liind-leg by preference in spinning their thread,) and the relation existing in
so many points between Respiration and Motion ; whilst, on the contrary,
the usual situation of the most important assimilative orgsuis is on the left
side, as we have already seen jus regards the Stomach, and as is likewise the
case with the Heart in the most perfect organism.

189

(D.) Sauria.

5. 609. Tlie respiratory organs are here generally formed
pretty nearly as in Tortoises. The Larynx is tolerably
simple, without vocal ligaments, and in the Chameleon is
furnished with a small sac-shapecl appendage: in most
Lizards, e. g. the Crocodile, it opens by a longitudinal
fissure ; but in the Chameleon by a transverse one. This
opening is always unconnected, being placed far back, and
somewhat covered by the posterior edge of the tongue in
the Crocodile, but in other species lying more forwards.
Many of the species belonging to this Order have the
power of emitting a sound by the voluntary tension of the
Kima and Glottidis, as is known to be particularly the case
in the Geckoes, where the tongue, which can be thrown
back like that of the Frog, appears to me to serve as an
Epiglottis. In the Larynx we already find, particularly in
the Crocodile, a large pointed anterior cartilaginous lamina
as a rudiment of the Thyroid Cartilage. (Tab. XII. fig-.
XIX. a.) The Trachea and Bronchi are nearly the same
as in Tortoises, i. e. composed of almost completely circu-
lar cartilaginous rings. In the Gecko, I find the Trachea
particularly wide and somewhat flattened. The Lungs
likewise form double . cellular sacs : they are almost the
same in the Gecko as in the Salamander, extending down-
wards far behind the Liver; whilst in the Crocodile, on
the contrary, at least as I observed in a young one, they
remain above the Liver, and, consequently, more in the
Thorax. (Tab. XII. fig. XIX. 1.) In the Chameleon,
the Lungs have been found furnished inferiorly with pecu-
liar finger-shaped appendages. The respiratory mechanism
is effected by the thoracic llibs and their muscles, without

190

■H

the assistance of a Diaphragm. We have already spoken
(§. 478.) of the laryngeal sacs of several Lizards, which
can be filled at pleasure by the expired air. They serve
partly to satisfy the necessity of a more extended respira-
tion in certain affections, e. g. Anger; and partly to facilitate
locomotion, e. g. in the Flying Lizard.

Section III. Respiratory and Vocal Organs of Birds.

§. 610. In the same manner that the diffusion of air
through all parts of the body in Insects marked the greatest
extent of Respiration in Invertebral Animals, so, also, is
it with Birds among Vertebral Animals, and for the same
reason ; though the structure of the respiratory organs in
general is much more uniform in them than in Insects.
The air here, also, enters chiefly by the nasal apertures,
from which it passes, by the longitudinal opening of the
posterior nares already noticed, (§.487.) across the Pharynx
into the Rima Glottidis : the latter, as in most Amphibia,
appears as a longitudinal fissure, and is covered with
papillae pointing backwards instead of an Epiglottis, of
which there is at most but a rudiment in the Ostrich. The
proper Larynx, which, for the purpose of distinction, we
may call the upper, is here composed of bones, and, as in
Amphibia, its anterior portion is formed by a large bony
plate terminating in a point superiorly, and corresponding
to the Thyroid Cartilage of Man. Posteriorly it is con-
nected with two smaller bones, and a middle oblong one.

191

which collectively correspond to the posterior part of the
Cricoid cartilage in Man.* Lastly, the Arytenoid Bones
are placed externally, bordering the sides of the Rima
Glottidis, and moved by peculiar muscles.

§. 611. From the length of the neck the Trachea in
Birds is more extended than in any other animals: its
rings are ossifiedf like the parts composing the Larynx,
and with the exception of the two uppermost, which may
be compared to the anterior part of the human Cricoid
Cartilage, form complete circles, but not infrequently in
such a manner, e. g. in the Heron and Swan 4 that they
are broadest alternately on the right and left sides, pre-
senting when viewed anteriorly and posteriorly a very
peculiar appearance of this kind,

_> =

“> =

~> =

The peculiar curvatures of the Trachea, which are fount!
in the males only H of several Gallinse, Aquatic and Wading
Birds, are particularly remarkable, being situated in the
male Crane, (Tab. XVI. fig. XI.) the Wild Swan, and
others, within the Keel of the Sternum (see §. 217.), or
merely below the Crop, as in the Grouse. The Trachea
in Birds is capable of being elongated by the muscles of
the Larynx and Lingual Bone, as well as by peculiar
/

* In the Larynx of a Dog, where the cartilages are partly ossified, I
distinctly observe the same three portions forming the broad back of the
Cricoid Cartilage.

f There are but few cartilages in Birds generally, as has been remarked
by Tiedemann (Zoologic, b. ii. §. 121. 539.), where he has given excel-
lent descriptions of the Vocal and Respiratory Organs of Birds.

j: Parsons, Philos. Trans. 1766. p. 215.

|| Another instance of the greater devclopement of the respiratory organa
in the male 9ex.

muscles proceeding from the Sternum and Fork-hone, ami
ot being shortened by the elasticity of the tendinous fibres
connecting the rings. This elongation and shortening,
as well as the length and bony nature of the Trachea,
but, above all, the extended diffusion of air through the
spacious cavities of the body, to be hereafter noticed, con-
tribute materially to strengthen and modify the Voice of
these Animals.

§. 612. The next point to be noticed is the second or
inferior Larynx, (Larynx bronchialis,) placed at the lower
extremity of the Trachea, which is peculiar to this Class
exclusively, existing in most of the species,* and particu-
larly important as a most essential vocal organ.f It is
formed in the following manner: a little before the division
of the Trachea there is a strong and solid ring, which is
divided from before backwards by two connected bony
processes, thus presenting a double aperture corresponding
to the right and left Bronchus, each containing a vocal
fissure formed by a duplicature of the lining membrane of
the Trachea.:}; The Bronchi themselves consist of semi-
elliptical rings connected by elastic fibres, the uppermost
being broadest and generally ossified, whilst the lower are
narrow and cartilaginous. Over the inner surface of the
Bronchi is stretched a thin transparent membrane, the
vibration of which contributes to the modification of the
Voice, and whence it may be called Membrana tympani-
formis. The branches of the Trachea are never of very

* According to Cuvier, it appears to be wanting in the Vultur papa only.

f There are experiments to prove, that even when the Trachea is divided,
Birds can emit their peculiar cry by the bronchial Larynx, though in a
weaker tone.

t In the Parrot, however, I have myself found that there is but a single
aperture, as the lowest ring of the Trachea is not divided.

193

considerable length, usually contain from 11 to 18 rings
and when cut from the lungs rapidly shorten themselves by
their own elasticity. Where they enter the lungs they
suddenly lose their cartilaginous rings ; whilst, on the con-
trary, their elastic or muscular fibres are continued for
some distance along the ramifications of the trachea.*

§. 613. The whole of this remarkable elastic apparatus
is moved by several muscles (3 to 5 pairs) in those Birds
which are distinguished for the modulations of their voice,
and for the power of imitating other tones, and even human
language, e. g. in Singing Birds and Parrots ; and is thus
adapted, by the shortening or elongation of the branches of
the trachea, tension or relaxation of the two rimse glot-
tidis, and of the membrane of the bronchi, for the produc-
tion of the voice ; which is again modified by the elongation
or shortening of the trachea itself, and by the contraction
and expansion of the glottis.f There are many other
species which have only a single muscle at the lower
larynx, the insertion of which is by no means the same in
all cases. Of this kind are, according to Tiedemann4 the
Eagle, Falcons, Owls, the Cuckoo, many wading and
some aquatic Birds, in which the voice is inflexible and
unvarying. Lastly, the muscles of this larynx are some-
times altogether wanting, as is the case in the Gallinse, and
in most Aquatic Birds, though in some of the latter, e. g.
An^s and Mergus, the males are distinguished by lateral,

Guvif.ii lias remarked these muscular fibre;, particularly in the Ostrich
and Cassowary.

t Hallf.r says, in his Elem. Phys. t. iii. p. ioO, “ His collectis adparet,
“ glottidem superiorem tcndi non posse, sed arctari : Glottidem inferiorem
“ arctari non posse, sed tendi : videri ergo ad variandos tonos, et in tensione
“ organi sonori, et in angustia ostiisonum edentis, varietatem locum habere.”

J On the Vocal Organs of Birds, in his Zoology , vol. ii.

VOL. II. O

194

though rarely symmetrical, dilatations of the inferior larynx:,
sometimes membranous and sometimes bony. (Tab. XVL
%. XII.)

§. 614. The lungs are here chiefly distinguished from
those of all other kinds of animals in this respect, that they
do not hang in the cavity of the trunk as unattached sacs,
but are attached in the form of two flattened masses of
spongy bright-red cellular texture to the posterior side of
a thorax, reaching to the pelvis. (§. 215.) They are smooth
anteriorly, furrowed posteriorly by the projecting ribs
between which they are lodged, and divided from each
other by the bodies or anterior spinous processes of the
dorsal vertebrae. (§. 213.) It is farther peculiar to the
lungs of Birds that they are not completely surrounded by
the membrane lining the thorax, and which, in animals with-
out a diaphragm, combines the characters of pleura and
peritoneum, but are merely covered by it on their anterior
surface, being immediately connected on the dorsal side to
the parietes of the thorax by short dense cellular structure.*
Lastly, it is most remarkable that they are not closed upon
their surface, but communicate by several apertures with the
neighbouring regions, so that the air escapes not only into
the cavities of the trunk, but also into those of the bones.
(See the Section on the Skeleton of Birds.)

§. 615. In the same manner that in Serpents we saw
the upper part of the lung with its thick sides terminating
inferiorly in a mere membranous sac, so also here various
processes of the internal membrane lining the common
cavity of the trunk form a series of cells, which, surround-
ing the other viscera, may be compared to that membra-
nous appendage of the lung of Serpents; and whence, also,
we might in this respect say, that in Birds the other viscera

* Strictly speaking, the human lungs are without the pleura, which is
here, however, still more evidently the ease.

195

are contained within the lungs. The openings of the hmg^
are situated at their lower extremity, and vary in number
from five to seven. Even the greater membranous cells are
not always similar ;* we may assume it as a general rule,
however, that every important viscus is surrounded by one
large, or even by two, cells ; thus, for instance, there are an
anterior and posterior cell to the heart, two great lateral
cells which surround the liver, and two particularly spacious
abdominal cells which inclose the intestinal and sexual
organs, &c. Distinct cells extend also to the surface of the
trunk, and convey the air to the clavicles, scapulae, humeri,
femora, and cervical vertebrae ; whilst, on the contrary, the
other bones of the trunk are furnished with air direct from
its cells. All these cavities are so intimately connected
together, that it is easy to inflate the whole body from any
one of them, or that (as Vrolik and Albers proved by
experiment) respiration can be kept up in an inverted
direction by them ; and, lastly, that the injury of any one
of them is sufficient to permit the escape of the heated and
rarefied air out of the body of the Bird, and render it unable*''
to fly.

§. 616. The respiratory motion of Birds is performed, as in
Lizards, though in a somewhat different manner, by the ribs
and sternum, and partly, also, by muscles, which may in
some respects be compared to a Diaphragm. These muscles
proceed, obliquely upwards in the form of flat bundles of
fibres from the middle of the lower ribs to the under part
of the lungs, where they are lost in the pleura covering
them; and thus by their contraction depress the lungs
themselves, expand their cells, and facilitate the ingress of
air into them. I have found them particularly developed
in the Parrot. The other and more important respiratory

* Very closely investigated by Merrem, in an Essay on the Respiratory1
Organs of Birds, in the Leipzig. Magazin f. Nuturk. 1783.

o 2

196

motion is performed by the muscles of the thorax, the
broad shield-shaped sternum, the ribs, consisting of two
articulated portions, and the immoveable range of dorsal
vertebrae,- (§. 215, 216.) all contributing to dilate and
narrow the thorax in the manner of a bellows, or of the
branchial apparatus of Fishes. When the sternum is
removed from the vertebral column, the angle formed by
the separate pieces of the ribs must be increased, and the
cavity of the trunk so much expanded, as to cause the
entrance of air, not merely into the lungs, but also through
them into the membranous cells of the trunk and its bones;*
and in greater quantity than in other vertebral animals, in
order to constitute an extended respiration not confined to
the lungs alone : on the other hand, the air is expelled from
the lungs by the contraction of the parietes of the thorax,
combined with the elasticity of the cells of the lungs. It
is remarkable that the air contained in the different cells
of the body, and so important for the locomotion of the
Bird, (§. 423.) is properly expired air, (i. e. has already
passed through the lungs, though it has by no means lost
the whole of its oxigen,) in this respect resembling the air
of the swim-bladder of Fishes. (§. 5S9. 609.) This is the
more interesting from the known fact that atmospheric air
becomes lighter in proportion as it parts with its oxygen,
and as nitrogen predominates, the weight of the latter being
to that of the former as 44 to 50. If we take into account'
that this air is farther considerably rarefied by the heat of
the body, we may understand the facility of flight thus
acquired by a consideration of the cause of the ascent of
balloons.

* It has been already mentioned (§. 219. 225.) that the air-cells of the
bones of the head aie supplied with air by the nasal cavities and eustachian
tube.

197

IV. Respiratory and Vocal Organs of Mammalia.

§. 617. In common with Man, the whole Class possesses
a simple superior larynx, a trachea divided into bronchi and
furnished with cartilaginous rings, two perfectly closed
lungs, and a thorax separated Irom the abdomen by a
diaphragm. As we may suppose the human type of these
organs to be known, we have here only to notice the parti-
cular deviations from it, and may easily trace the approxi-
mations to inferior formations. In this as in the two
preceding Classes, the air is taken in principally through
the nasal passages; but whilst we found that in Amphibia
and Birds the. apertures of these canals (anterior and poste-
rior nasal foramina) could generally be completely closed
by peculiar muscular fibres, the same mechanism is here
limited to the occurrence of a contraction either by the
circular fibres of the external nares, or by the velum palati,
or parts which supply its place. The Amphibious Mam-
malia, however, as well as the Cetacea, form an exception
in this particular, as in them the perfect occlusion becomes
again possible, partly by means of the fissures of the ex-
ternal apertures of the nares, and partly by means of
valves within the nasal canals themselves. (See the
Section on the Olfactory Organs of Mammalia.)

§• 618. In proportion as the nasal canals in Mammalia
can be less perfectly closed than in the preceding Classes
must the aperture of the trachea itself be covered with more
precision, — an object effected by the epiglottis peculiar to
this Class, which we may consider merely as a repetition

198

of the retroverted tongue of many Amphibia, e. g. Frogs.
As far as is known, it exists in all Mammalia,* though
exceedingly diversified in its form. In Whales and Por-
poises, the larynx of which has been so often noticed as
projecting far upwards in the fauces, it is small, with its
edges* attached to the larynx, and the aperture of the latter,
consequently, more in the form of a transverse fissure. In
other Mammalia its circumstances approximate more and
more to the human model, though in many it is propor-
tionally much larger, pointing directly upwards; in some
cases even so far as to extend behind the velum palati,f
thus rendering the passage for air more complete, and in
most of the larger animals is moved forwards by a peculiar
muscle (hyo-epiglotticus). The epiglottis is frequently
divided at its superior extremity, e.g. in the Seal, (Tab.
XX. fig. V. a.) Ant-Eater, and Hare; in this respect
reminding us of the divided point of the tongue in Am-
phibia.

§. 619. The larynx itself in the Mammalia in general
consists of the same number of larger cartilages as in Man ;
whilst of the smaller cartilages of Santorini and Wris-
berg, the former, according to Wolff, f are wanting in
Hyienas, Lions, Cats, Otters, Seals, Sloths, and others,
whilst the latter exist in Apes only. The larynx is most
singular in the Cetacea, presenting a pyramidal cavity
without vocal ligaments, whence these animals, if not dumb,
are at least incapable of making any thing more than an
inarticulate murmur. The larynx of Opossums and Roden-
tia presents an evident affinity in many points to that of

* Its existence has been incorrectly denied in the Mole by Jacobs.
(Talpce Europ. Anatome. Jena?, 1815.)

-j- This has been observed in the Elephant, but I find it also in the Cal
)ipix rosa/in.

| Dc Ortjano Vocis Mammalium. Berol. 1812, p. 12.

199

Birds. Thus, in the Kanguroo, according to Cuvier, the
arytenoid cartilages form two-thirds of the ligaments of the
glottis, whilst the vocal ligaments are nearly, and the
ventricles of the larynx altogether, wanting. So, also, the
vocal ligaments and ventricles are wanting in the Porcu-
pine and many other Rodentia, but both exist in the Rabbit.
The larynx of Sloths and Armadilloes, likewise, is ill fitted
for the production of voice, in consequence of the imperfect
formation of the vocal ligaments and ventricles.

§. 620. Among the Pachydermata the vocal ligaments
and the ventricles are wanting, according to Cuvier, in the
Hippopotamus. In the Elephant there is merely an imper-
fect rudiment of the ventricles. In the Pig, too, they are
but inconsiderable, but lead to two spacious cavities, which
appear to contribute to the production of the grunting
voice of this animal. The larynx of the Ruminants is
tolerably simple, and, except in the Camel, is usually with-
out the superior ligaments of the glottis and the laryngeal
ventricles. In several Antilopes there is a remarkable mem-
branous cavity between the epiglottis and the thyroid carti-
lage; which in the Rein-Deer, according to Camper,* is
dilated into a considerable membranous pouch. It resembles
the laryngeal sac of the Amphibia, and is probably con-
nected with the necessity for a greater supply of air in
these swift-footed animals. The Solipeda are distinguished
by very spacious vocal sacs, and have besides, like the
Antilopes, a membranous cavity situated above the upper
edge of the thyroid cartilage. In the Horse the vocal
ligaments, as described by Wolff, f are broad and strong,
and present on each side a large oval aperture, leading to
spacious cavities. These ligaments are also covered by a
delicate semilunar fold of membrane, the vibrations1 of
which produce the peculiar neighing of this animal. The
♦ Nuturgeschichle des Orang- Utang, Tab. VIII. f Luc. cit. p. 36.

200

entrances to the anterior and lateral cavities are smaller in
the Ass.

§. 621. Among Carnivora the Lion is particularly re-
markable for the very considerable extent of the larynx,
corresponding to the powerful roar of that animal. In this
case the anterior contribute more than the posterior vocal
ligaments to the formation of the voice, and there are not
any vocal cavities : such, also, is the case in the remaining
species of the Cat Genus. In the Dog, on the other hand,
the vocal cavities are considerable, and the inferior ligaments
strong: the extent of the cavities is considerable in the
Wolf also. In the Bear Genus, on the contrary, accord-
ing to the examinations of Cuvier, the anterior and pos-
terior vocal ligaments are on the same level. The most
human-like formation of the larynx is found in Apes; but,
notwithstanding, the finer and more important modulations
of voice are impeded by the presence of sac-shaped dila-
tations or appendages, which interrupt and obscure the
sound, though Vjc£. d’Azyr and Lordat* have rendered
it very improbable that the incapability of speech is to be
attributed solely to these sacs. In the Orang-Utang, where
they have been described by Camper, they present them-
selves as two oblonr sacs, not always symmetrical, between
the body of the hyoid bone and thyroid cartilage, opening
into the upper part of the ventricles of the larynx, and
appearing like a hernial dilatation of them.f

§. 622. Lunwi<'4 found two such unsymmetrical sacs in
the Magot (Simia inum), and I myself observe one such
in the Lion Ape (S. rosalia), though not between the

* Clsirvations sur qvelques Points de V Anatomic du Singe Vert. Paris,
'1804.

f It would l>e important to examine the mode of origin of these sacs,
and to ascertain if they may not actually be produced by respiration after
biuh. -

} Grundriss der Naturgeseh. d. Mensch. Tab. I. II.

201

Cricoid and Thyroid Cartilages as described by Cuvier,*
but between the Hyoid Bone and Thyroid Cartilage. It
is found in the same situation, according to Wolff, + in the
Simia sabca ; and, also, according to Camper and Cuvier,
in many others, e.g. Maimon, Marmon, Sphinx, Cynomolgus,
Veter. In other species, on the contrary, the sacs are alto-
gether wanting, e. g. in the S. hamadryas , rubra , and sinica.
The tympanum-like cavity before noticed (§. 506.) in the
body of the Hyoid Bone of the S. seniculus is particularly
remarkable, and is occupied by two unsymmetricalj sacs
which open into the ventricles of the Larynx. In this case
the cavity by its resonance contributes much to strengthen
the voice. A similar effect is produced by a membranous
dilatation between the Cricoid Cartilage and Trachea,
described by Cuvier, in the Coaita (S. paniscus ). As to
the general character of these laryngeal sacs, we need
only repeat what has been said with regard to those of the
Ruminants .(§. 620.), remembering only that in the Cha-
meleon there exists a similar expansion of the Larynx.
Here, also, we must notice the structure of the Larynx
as described in some American Apes (S. apella and capu-
cina) by Cuvier, in which the air passing between the
vocal ligaments takes a curved direction between cushions
of fat, thus resembling the structure of a flute, and explain-
ing the flute-like voice of these animals.

§■ 623. As to the form of the Cartilages of the Larynx,

* Is it not possible that the origin and extent of these sacs, or even their
situation, may vary in different individuals of a species ?

f Loc. c it. p. 1.

t Here, as well as in the S. inuus, according to Ludwig, and the S, sil-
vanvs, according to Blumenbach, the right sac is larger than the left, being
another proof in favour of what has been already said of the predominance of
Respiration on the right side. Is it not probable, too, that this cavity in
the ITyoid Bone is formed after birth?

202

that of the largest, the Thyroid, is subject to many varieties,
of which the following are the most essential accordirig to
Wolff and Rudolphi : the angle at which its sides meet
is usually obtuse as in Man, but more acute in the Guinea-
Pig, Sheep, and Horse ; — 2d, the notch in its upper margin
is usually wanting, except in the Badger and the Rumi-
nants, its situation being commonly occupied by a larger
or smaller process ; — 3d, its inferior margin in most species
of Mammalia presents a much deeper excavation than in
Man, e. g. in the Hyaena, Weasel, &c. but more particu-
larly in the Bear and Seal, where the two lateral halves are
connected in but a small part of their extent; — 4th, of the
Cornua, the inferior are generally largest, but the superior
in the Stag, Roe, and Lynx ; — 5th. In some Ruminants,
particularly the Antilope gutturosa , the anterior surface of
the Thyroid Cartilage forms a considerable projection.
The form of the Cricoid Cartilage, also, presents many
peculiarities in different species : in .the Roe, for instance,
it has a projecting sharp ridge on its anterior side ; in the
Bear is divided anteriorly into two halves connected only
by tendinous fibres; in the Hyaena it ascends high on the
dorsal side of the Trachea; &c. whilst in the Dog and
Badger it is very similar to that of Man. The varieties
in the form of the Arytenoid Cartilages are equally great:
they are proportionally large in the Bear, Hyaena, Weasel,
Otter, Beaver, and Mouse ; whilst, on the other hand, they
are small in Apes, the Badger, Hedgehog, Dog, and par-
ticularly the Wolf.

§. 624. In the Trachea of Mammalia, though essen-
tially corresponding to the human type, we find many
approximations to earlier formations. Of this kind are the
complete rings of cartilage which are found precisely in
those species most nearly related to Birds, e. g. in some
Itodentia, Maki’s, and Chiroptera. Such, also, is the case

203

in the Phaianger, the Galeopitheci, the Mococo (Lemur
catta ), and the Beaver. Besides these, perfect rings have
been found in several amphibious Mammalia, e. g. the Seal,
(at least the 12 upper rings,) the Manati, and Porpoise,
analogous to the perfect rings of the same part in many
Amphibia, e. g. Tortoises. A second remarkable recur-
rence of formations, already noticed, occurs in the descrip-
tion given by Daubenton and Wolff of the course of
the Trachea in the Thorax of the Sloth (Bradypus tridac-
tylus), in which it descends on the dorsal parietes of the
chest between the Lungs, and then turning forwards re-
ascends in order to divide into two Bronchi. (Tab. XX.
fig. VIII.) The extremities of the cartilaginous rings are
here in immediate contact, and it may be stated generally,
that in many species, particularly such as are related to
those which have already been described as possessing per-
fect rings, the membranous interval between the extremities
of the cartilages of the Trachea on the dorsal side is ex-
ceedingly small, as, for instance, in most Quadrumana and
Itodentia, several Canivora, Ruminants, &c.* f

625. The length of the Trachea is regulated chiefly
by that of the neck, though without any proportion between

* This is the case, also, in the Mole, though its Trachea is farther distin-
guished by the distance at which the rings are placed from each other, several
of /them, also, being divided, and others extending only half way round the
tube.

f In the W hite-throated Sai and Alouatte, the rings of the Trachea
present two very opposite conditions. In the former they are very complete
towards the lower part, overlapping each other in such a manner as not to
leave any membranous interspace. In the Alouatte, they scarcely extend
round half the circumference of the tube, and still less so in the bronchi :
jn the former, they are narrow and remote from each other ; and in the
bronchi, disappear as the tubes enter the Lungs. This structure must evi-
dently render these canals capable of great changes in length and diameter,
and must materially modify the voice of the animal. (Cuvier, Comp. Anat.
jv. .311.) — Translator.

204

it and the number of its rings, of which there are, for
instance, 53 in the Stag, and '73 in the Seal. In most
others the number of rings is smaller, though generally
more considerable than in Man. The division of the
Trachea into the Bronchi is usually simple, without any
trace of a second Larynx, and it is only in the Lemur
macaco that Daubenton* observed a tympanum-like dilata-
tion of the two short Bronchi. A triple division, however,
has been observed by many anatomists in Ruminants, ( e . g.
the Stag, Roe, Ox, Sheep, Camel, &c.) and Swine, (the
common Pig and Peccari.) Wolff and Rudolphi found
this third division given off between the 43d and 44th
rings of the Trachea in the Ox and Sheep. In the Goat
I reckoned 8 rings between this lateral branch and the
division into the Bronchi. It is always found on the right
side, and, as Meckel! has remarked, corresponds to the
more considerable size of the right Lung. The rings of
the branches of the Trachea in Mammalia generally dis-
appear gradually, as those canals ramify in the substance
of the Lungs : in some Opossums, on the contrary, they
terminate very abruptly, according to Cuvier, in the same
manner as in Birds. The muscular fibres of the Trachea
of Mammalia appear to be confined exclusively to the
dorsal membranous part.J

* Buffos*, Hist. Nat. t. xiii. p. 207.

f Translation of Cuvier’s Comp. A not. vol. iv. p. 154.

f In Man, the Trachea has from 17 to 20 rings ; in the Camel, 74 ; the
Stag, 53; Mouse, 14; Hedgehog, 18; Phascolome, 20; Rat, 21 ; Beaver,
22; Simia sabaa, 24; Rear, 28; Ilvama, 30; Lion. Cat, Dog, Rabbit, 38;
Pig, 3S to 40; Lynx, Guinea-pig, 40; Hare, 44; Wolf, Sea-Otter, Sheep,
50 ; Roe, 53 ; Pole-cat, 07 ; Seal, 78. In the Simia seniculas, Lion, and
Bear, the space between the extremities of the Rings is very great, so as to
permit of a considerable reduction of the diameter of the tube they form.
( Rudolph i, Physiologic, i. 38 3.)— -Translator.

§. 6 26. In considering the Lungs themselves, we find
a structure which is generally very closely related to that
of Man; but, at the same time also, meet with a remarkable
approximation to the sac -shaped simple Lungs of the Am-
phibia, viz. in the amphibious and fish-like* Mammalia. In
these species, and more particularly in the Cetacea, the
Lungs are not perfectly divided into several lobes as in
Man, and are continued in the form of narrow elongated
sacs low on the Spine, a disposition favoured by the form
of the Thorax to be hereafter noticed : they are farther
distinguished by the very small size of the cells, which,
however, communicate very freely together, so that air
impelled into a small ramification of the Trachea distends
the whole lung; nay, the pulmonary cells, here, as in Am-
phibia, have an extraordinary degree of contractility, and
so completely empty themselves of air, that from its solidity
and appearance, HuNTEitf compares the pulmonary sub-
stance to the Spleen of an Ox. The Lungs are almost
precisely similar in some Amphibious Mammalia, whilst in
others, on the contrary, they more nearly resemble those
of the other animals of the Class. Of the former kind,
according to Daubenton,^ is the Manati, in the foetus of
which he found the Lungs forming long flat sacs, separated
from the Sternum by the large heart, descending below
the Liver and Stomach, and penetrated at their upper
extremity by the Bronchi : of the latter description is the
Seal, in the Lungs of which fissures (lobular) have been
observed by several anatomists. ||

* They here again serve as Swim-bladders. (See §. 430.)

f Observations on the Structure and (Economy of Whales, in the Philos.
Trans. 1781. p. 419.

t Buffon, Hist. Nat. t. xiii, p. 4-29.

|) The Lungs of the Dugong arc very elastic, and the air-cells near the
surface double the size of those in other parts. The cartilaginous rings sur-

20 (T

§. 627. The parenchyma of the Lungs, in other Mam-
malia, is not essentially different from that of Man, though
it must be regarded as a very distinguishing character in
their structure, that, according to Daubenton, both Lungs
in the Sus tajassu present considerable vesicular appen-
dages on the dorsal surface, which, however, may very
possibly have been the result of disease. The varieties
in the number of the lobes in the different species are,
however, exceedingly numerous. We may remark gene-
rally, that the number is usually greater than in Man, and
greater in the right than the left Lung, a point on which
Cuvier has given a copious Table, the general result of
which is, that in most species the right Lung has from 3 to
4, and the left from 2 to 3, rarely 4, lobes. Less frequently
still each Lung is undivided, e. g. in the Elephant, Rhino-
ceros, Horse, and Lama, (resembling the amphibious
species,) or the Bat and Flying Maki, (where it is ana-
logous to the single lungs of Birds.) Farther, in the whole
Class we usually (as in many Amphibia and in Man) find
the right Lung larger than the left, though, as we shall
hereafter see, the Heart is ordinarily placed in the middle
of the Thorax : on this account, a distinct lobe of the right
Lung is situated between the Diaphragm and the Heart,
which is at some distance from it. Hence, 1 was the more
surprised to find that in the Mole, where the Heart is
turned to the left side, the right Lung exceeds the left for
the same reason as in Man, and even in a still greater

§. 628. As to the mechanism of Respiration in this
Class, we here first meet with a perfect muscular septum
(Diaphragm) between the cavities of the trunk which con-

rounding the bronchi present a certain degree of analog)' to the parietes of
the Trachere of Insects, being arranged around the tube in oval spiral convo-
lutions. (Home, Phil. Tram. 1820. p. 2.) — Translator.

SOT

tain the Lungs and the abdominal viscera. It here, con-
sequently, represents the muscular septum dividing the
branchial apparatus (Thorax) from the Abdomen of Fishes,
with this difference, that, in this instance, the Heart is
included within the cavity containing the respiratory organs,
the Diaphragm farther offering an analogy to the tendinous
membrane moved by muscles, which connects the Lungs
of Birds to the dorsal side of the Thorax. . The Diaphragm
of amphibious and cetaceous Mammalia approximates to
these earlier types of formation. In the latter, the very
strong and fleshy Diaphragm is attached to the dorsal side
of the cavity of the trunk so low down, that it ascends
considerably in order to be connected in a peculiar manner
with the upper and anterior extremity of the abdominal
muscles. The Thorax is, consequently, very long at the
back part, the space being occupied by the elongated Lungs;
whilst the anterior part is very short, and almost exclusively
occupied by the Heart. The Lungs, therefore, (in the
same manner in Birds,) may be said to lay behind, rather
than above, the Diaphragm : the latter organ, which, from
its connection with the abdominal muscles, as well as its
own strength, is capable of exerting much force, acting in
the same manner as in Man, forms the principal agent in
Inspiration, which is rendered difficult by the aqueous
medium in which the animal is placed ; whilst, on the con-
trary, Expiration is effected by the elasticity of the cells
of the Lungs. The respiratory motions of the amphibious
Mammalia agree pretty closely with the above description,
and in them, also, particularly the larger kinds, we evidently
observe a very considerable exertion of force in breathing.
1 he species of both Orders, and particularly the first, can,
as is well known, dispense with respiration for a considera-
ble interval.

In the remaining Mammalia, the structure of the Dia-

208

pliragm, as well as the respiratory motions, have so few
peculiarities, that it would be needless to enter into a de-
tailed description of either, — the more so, as we are
enabled to refer to these points in the human body as a
general model.

§. 629. Having thus considered the whole series of the
very varied forms of the respiratory apparatus, it only re-
mains to remark upon the peculiarities which distinguish
that of Man. As we already found that in the Systems
of the Vegetative Sphere for the ingestion of materials,
the human peculiarities were observable in so far only as
related to the sensibility of those organs, so are we led to
a similar conclusion as regards these organs employed in
the volatilization of organic matter. We have found that
Man is not distinguished beyond other animals either by
the force or extent of his Respiration ; nay, that he is ex-
ceeded in both particulars by many; and, consequently,
that we do not discover the superiority of the human type
in the respiratory organs, considered merely as such. If,
on the other hand, we view the respiratory organs as an
index of the conditions of the mind and of its feelings, what
animal is there that can be compared with Man? It is
true, that the animal when it possesses Voice employs its
tones, or even the sound (without Voice) produced by
other parts, to express various affections ;* but as thought
is produced in the Head of Man as the crown of a com-
pletely independent and harmonic organization, so, also,
does Speech receive its full perfection in the mouth of
Man, as compared with its rude and imperfectly articulate

* It deserves to be remarked, too, how Respiration, which is in the
Vegetative what Motion is in the Animal Sphere, serves like it to convey
the influence of internal conditions to external ohjects; more particularly,
as Vocal organs are formed by the combination of Organs of Motion ami
Respiration.

209

tones in the animal world. Nay, Tone alone, without any
reference to the expression of ideas, has the power of indi-
cating the minutest shades of passion and mental emotion
(Singing) ; and, as such, is to the Feelings what Speech is
to the Intellect.

Lastly, I may here remark, that the greater strength
and ability of the right upper extremity in Man evidently
coincides with the greater size of the right Lung, and the
predominance of Respiration on the right side ; and that
they cannot by any means be considered as the result of
habit alone.

III. Of the different Forms of Repetition of
the Respiratory Organs ; or, Of the
Secretory Organs.

A. Repetition of the Respiratory Organs in the Digestive
System; or, Of the peculiar Organs of Secretion belonging
to the Intestinal Canal.

§. 630. In order that the nutritive matter taken into
the Intestinal Canal may be truly assimilated to the body,
it is necessary that its individuality should be previously
destroyed ; for we cannot conceive how a body, so long as it
in itself forms an independent and complete whole, should
▼ol. ii. p

210

become an integral part of another Organism. We hence
understand, not only why animals which live on others
ordinarily destroy their prey previous to swallowing it, but
also, the object of the bruising of animal and vegetable
matter by teeth, or by parts supplying their place : such,
also, is the object of the intermixture of peculiar fluids,
which, by their chemical or dynamic qualities, act upon
the alimentary matter, destroying or dissolving it, and
annihilating its individuality. The same effect is produced
when Man, by various artificial processes and mixtures,
changes, or almost wholly destroys, the peculiar nature of
his food previous to swallowing it. We have already con-
sidered the various provisions for taking and dividing the
food, and next proceed to the structures which effuse
various secretions into the Intestinal Canal, thereby shew-
ing that the secretory nature of the cutaneous surface is
repeated in the Intestinal Canal, in the same manner that,
on the other hand, the skin in many animals presents itself
as an absorbent surface. It must be observed, however,
that these secretions, in correspondence with the assimilative-
character of the Digestive System, are not, like others,
lost to the body, ( e . g. Urine, Perspiration, &c.); but, on
the contrary, contribute essentially to the digestive process.
Of the Organs belonging to this Class, we must first con-
sider those which, being placed at the entrance of the
Intestinal Canal, serve to prepare the fluids that first act
on the nutritive matter, and that frequently even like
actual poisons.

211

Section I. Salivary Organs,

1 . Zoophytes.

§. 631. Distinct organs are usually wanting for the
secretion of Saliva, as well as for so many other functions
in this Class ; particularly as the cavities of the mouth and
stomach are so far identical that they appear but as one, in
which we are unable to distinguish the saliva from the
gastric fluid. But, that these fluids here act powerfully in
destroying the individuality of the alimentary materials,
and even as chemical solvents, is proved by the Medusae,
which, as already noticed (§. 433.), are capable of dissolv-
ing and digesting very solid substances. Cuvier found
distinct salivary organs only in some of the Holothuriae, in
the H. treniula , consisting of twenty little irregular blind
sacs around the mouth, and in the H. pentactes , as two
similar, but larger ones.

/ 2. Salivary Organs in the Mollusca.

§. 632. In the Acephala, where, as in many Zoophytes,
the (Esophagus is so short that the mouth frequently appears
to be the orifice of the Stomach, proper salivary organs are in
most instances wanting. I have not been able to discover
them either in the Fresh-water Muscle nor in Ascidise: in
the Teredo, however, Home found two considerable glands
on the (Esophagus, which, by the secretion of solvent fluids,

p 2

212

appear to facilitate the boring of these animals into the
wood-work of Ships and Dams.

§. 633. These organs are much more developed in the
Gasteropoda, where they are ordinarily attached to the
CEsophagus as a pair of Glands of considerable length,
being surrounded (either themselves or their excretory
ducts) by the nervous circle of the neck. In the Helix
pomutia , they are expanded over the anterior part of the
Stomach, and empty themselves by two ducts into the cavity
of the Pharynx. (Tab. III. fig. III. d. d. fig. V. i.) In
the viviparous Snail, they are shorter and more compressed,
(fig. X. v.) ; in the Aplysia, on the contrary, they are
longer, (fig. VII. u. u.) In the Genus Doris, there is,
moreover, an accessory salivary gland.

§. 634. Lastly, the salivary organs are usually still more
developed in the Cephalopoda, where we generally find
two pairs of them.* In the Sepia octopodia , I find a smaller
upper pair close to the pharynx (Tab. IV. fig. II. c.), and
a lower pair somewhat larger, flat, heart-shaped, and near
the CEsophagus (d.) : the excretory ducts of these last
unite into a single canal, ascending upwards and opening
near the excretory ducts of the upper glands. The arrange-
ment is similar in the Cuttle-fish, (S. officinalis.)

3. Salivary Organs in the Articulata.

§. 635. All examinations have hitherto failed to discover
salivary vessels in Vermes or Crustacea, which may probably

• We have here a proof that the greater or less, or even deficient, secre-
tion of Saliva is not in any way connected with the mode of life, inasmuch
as we find highly developed salivary organs in these and other Mollusca that
Ifve in water. Generally the mode of life is regulated by the organization,
and not the reverse.

213

depend upon the shortness of the (Esophagus in the latter
(§. 632.), and the close relation of the former to Zoophytes.
It may, however, be proposed as a question, whether we do
not find the character of salivary glands in two little green
bodies placed at each side of the stomach in the Cray-fish,
and which, though long ago described and represented by
Rosel,* I do not find mentioned by Cuvier. (Tab. VI. fig.
IV. h.) At least, they are placed near the Stomach, as
was the case in several Mollusca; and it is remarkable, that
the Crab’s Eyes, as they are called, are formed immediately
over them, whence they might be considered as salivary con-
cretions, particularly as it is probable that they are ulti-
mately rejected through the mouth. In Insects, on the
contrary, these organs not infrequently exist, though not
as true glands, but as vessels terminating in blind extremi-
ties. Among the Gnathaptera, they have been observed
particularly in Spiders, the venom organs of which, already
mentioned, (§. 451. compare with §. 630.) consist of oblong
bladders, and terminate by excretory ducts in the points
of the mandibulaj. Some Scolopendrae, also, as well as
several Coleoptera, and the Aptera, Diptera, and Hemip-
tera, furnished with organs for stinging and sucking, appear
to infuse similar secretions into the injuries they inflict, as
is proved by the poisonous effects from the former, and in
the latter by the smarting of the wounds and swelling of
the &kin. Ramdohr, also, states that the salivary vessels
of several Diptera and Hemiptera have been detected ter-
minating either in the sucking proboscis, the pharynx, or
the stomach. The Gryllus verrucivorus even derives its
name from the saliva poured into the mouth, which, when
the animal is allowed to bite a Wart, causes it to disappear.
The salivary vessels are more precisely known in the

• IiurhlmbeluHtigungen, tb. iii. b. ii. s. 322.

214

Willow Caterpillar, where! they open by means of excretory
ducts into the mouth, anti consist of two sacs an inch long
placed at the sides of the (Esophagus, and having much
similarity to the salivary vessels of Spiders.

Before quitting the salivary secretions of invertebral
animals in general, and Insects in particular, we must
devote a few words to the Spinning Organs of Caterpillars,
inasmuch as they present a close relation both in form and
situation to salivary organs. They consist of thin vessels
with a blind termination, one placed on each side of the
Intestinal Canal, (Tab. VII. fig. XI. h. 1.) and much ex-
ceeding the length of the body, being a foot long in the
Silk-worm, for instance : they ultimately terminate by
delicate excretory ducts in an opening beneath the spinning
tubercle on the lower lip, (nearly in the same manner as
the Sublingual Glands beneath the Tongue,) where their
fluid, becoming condensed by the action of the air, is drawn
into threads which are employed in forming webs for the
purpose of metamorphosis. As is well known, we are
indebted for Silk to the beautiful web of the Caterpillar of
the Phalaena Mori , where the Cocoon, weighing 2\ grains,
consists of a thread 900 feet long. In point of . character,
these organs are evidently repetitions of the spinning
apparatus at the anus of less perfect Insects, e. g. Spiders :
and it is interesting to observe, that the web of the Spider
is chiefly employed to form a covering for the ova, thus
serving to favour the developement of the young; whilst
in the Caterpillar, the Cocoon is subservient to the meta-
morphosis and developement of the animal itself.

215

4. Salivary Organs in Fishes.

§. 636. The short and capacious (Esophagus almost
invariably existing in this Class, as well as the rapidity
with which the food is swallowed, (not being detained in
the mouth, and rarely masticated,) are the causes which
lead to the almost uniform deficiency of proper salivary
organs, and consequently to an approximation to Zoophytes
in this particular. The deficiency is, indeed, in some
degree compensated by a more copious secretion of mucus
from the lining membrane of the mouth, where, conse-
quently, we find very evident layers of mucous glands,
e. g. in the Carp Genus, and also, according to Cuvier, in
Rays and Sharks.

5. Salivary Organs in Amphibia.

§. 637. The Batrachian and Chelonian Orders approxi-
mate to Fishes in so far as, that instead of single large
glands there are rather flat layers of glands (mucous folli-
cles) under the internal membrane of the mouth, and par-
ticularly the Tongue, which, secreting a tenacious mucus,
supply the deficiency of Saliva. In Serpents and several
Lizards, on the contrary, the Salivary Glands are more
distinct. In the former, the Venom Glands are particularly
remarkable, which, as already mentioned, (§. 474.) dis-
charge themselves by a divided tooth, precisely as the
Salivary Vessels in Spiders. These Glands are here of
considerable extent, are situated behind the Orbit above
the joint of the jaw, and are compressed by a peculiar

216

muscle. (Tab. XII. fig. III. c.) In those Serpents that
are not venomous, two small glandular layers on each side
of the margin of the Superior Maxilla appear to be the
only remains of these larger Glands ; and I was struck to
find that in the Coluber nalrix , and still more in the C.
thuringica, the Tendon of a muscle placed upon the back
part of the neck passes over the joint of the jaw, and
divides into several fibres which are inserted into the scales
of the upper jaw. It is easy to see how the tightening of
this tendon must retract those scales, and so promote the
flow of Saliva. In Lizards, Cuvier states that there are
sometimes layers of mucous Glands similar to those in
the two first Orders ; at others, Glands on the margin of
the upper jaw, as in the Serpents that are not venomous;
and lastly, that they are sometimes altogether wanting.

6. Salivary Organs of Birds.

§. 638. It is in those Birds which live on vegetables that
the salivary organs are most strikingly developed, f though
the glands themselves in form and position resemble those
of the preceding Classes, being placed immediately beneath
the internal membrane on the floor of the mouth, each
glandular granule pouring its secretion separately into the
cavity. Ordinarily, too, the secretion is less properly sali-
vary than mucous, i. e. thick and tenacious. This is parti-
cularly the case in the Woodpecker, where it forms a viscid
coating to the tongue, which is employed for taking its
prey. (§. 484.) The largest pair of these glands is usually
placed between the rami of the lower jaw, (glandulae sub-
maxillares,) and in the Turkey ( Fab. XV. fig. X. d. d.*) is
f Tif.demann, Zoologic, b. ii. s. 393.

217

even double. In the Accipitres these glands are smaller
than in herbivorous Birds, but at the same time more
numerous. In the Sparrow-Hawk, Tiedemann has described
five sets of them ; of which one pair is situated above the
articulation of the jaws, corresponding to the poison glands
of Serpents, and at the same time to the parotid glands in
Man ; another pair, on the contrary, is placed on the palate,
pouring out their secretion towards the arched tooth-like
extremity of the (§. 482.) upper billf by two ducts running
along the roof of the palate; the remaining sets, as in
other instances, are placed at the floor of the mouth.

7. Of the Salivary Organs in Mammalia.

§. 639. It affords an additional proof of the close con-
nection between the Cetacea and Fishes, that, according
to all examinations up to this time, the salivary glands are
altogether wanting in the former, and that even in the
amphibious Mammalia their size is inconsiderable. On the
contrary, they are in a corresponding degree more deve-
loped in the Rodentia and Bats, approximated as those
animals are in so many respects to Birds : the submaxillary
glands in them being of extraordinary magnitude as com-
pared with the parotid, sublingual, and buccal glands, pos-
sessed by most Mammalia in common with Man. In the
Edentata, e. g. the Echidna and Ant-Eater, the parotid
glands are wanting; but in the latter a peculiar gland

f As was already the case in Spiders, so also in Serpents, in Birds, and,
as we shall find, even in Mammalia, there is a uniform relation between the
salivary organs and the instruments employed in mastication, the saliva
being generally poured out near the most efficient of the organs employed
for that purpose.

218

opening on the lower lip serves to secrete the viscid mucus*
which, when spread over the tongue, (§. 508.) is employed
for taking small Insects. Generally, the rule applies to
Mammalia as to Birds, that the salivary glands are most
developed in the herbivorous species. This has been
already mentioned as regards the Rodentia, in which the
great power of the cutting teeth is combined with great
developement of the salivary glands, which also evacuate
themselves chiefly towards the anterior part of the mouth.
These glands are likewise very large in the Ruminantia
and Solipeda, in which the saliva from the parotid and
buccal glands is evacuated near to the molar teeth, as being
the most efficient organs of mastication. Nay, in the Ox and
Sheep the secretion of the former is increased by a pecu-
liar gland seated in the orbit and zygomatic fossa, and
described by Nuck in the Dog, with some variations.
According to Cuvier’s statements the parotid glands are
particularly large in Apes.f

f In the Two^toed Ant-Eater, besides the salivary glands, properly so
called, there is another of a different character, which furnishes the viscous
fluid with which the tongue is coated for the purpose of securing its prey. It
is oval, flattened, and descends in front of the tendon of the Masseter, behind
the angle of the lips, and along the margin of the lower lip as far as its
middle. Its duct opens into a groove at the commissure of the lips. When
the gland is compressed, the orifice of the duct gives issue to a thick, white,
and tenacious secretion. (Cuvier, Comp. Anat. iii. 216.) — Translator .

219

Section II. Of some other Secretions poured into the
Intestinal Canal in the remaining parts of its
course , in the higher Classes of Animals.

640. Under this head must be classed the mucus of
the nasal cavities, which is poured into the cavity of the
mouth or fauces in all animals in which there are posterior
openings to the nares; consequently, in Amphibia, Birds,
and Mammalia, the amount of the secretion corresponding
to the extent of the nasal cavities. The course which
these fluids take in order to reach the commencement of
the oesophagus having been already noticed when describing
the organs of Smell and the Fauces, requires no farther
explanation, except as regards the anterior palatine open-
ings, (foramina incisiva sive naso-palatina,) which are found
in most Mammalia, and pouring out a portion of the nasal
mucus in the region of the superior incisores, remind us,
on the one hand, of the palatine glands in certain Birds,
(§. 638.) and, on the other, are evidently a repetition of an
oarlier form of the posterior nasal apertures, which, in
Aiqphibia, frequently open immediately behind the anterior
part of the margin of the superior maxilla.

§• 641. These apertures, which had been already re-
marked by Steno, and the existence or non-existence of
which in Man has given rise to much anatomical contro-
versy, have recently been very well described by Jacob-
son.* They are particularly distinct in herbivorous

* Bulletin des Sciences de la Soc. Philomatique. Avril, 1815. See Cu-
vier's Report on that Essay in the Annales du Museum d'Hist. Nat. t.
xviii. p. 4. 12.

220

Mammalia, e. g. in the Ruminantia and several Rodentia ;
and as in them the connection between the nose and mouth
is established by means of tolerably long canals situated in
the openings of the bony palate, and provided with peculiar
cartilaginous sheaths, and many fibrillse of nerves, Jacob-
son thought himself justified in considering this apparatus
as a peculiar organ of sense, the organ of the Instinct which
directs the animal in the choice of its food. With this view
we, however, cannot coincide, inasmuch as we can by no
means consider this and other instincts of animals as residing
in any such individual organ ; though at the same time
without intending to deny that a very free communication
of this kind between the organs of Smell and Taste may
tend to favour and increase the activity of both. But that
these openings are not common to all the Herbivora has
been remarked even by Jacobson, as regards the Horse,
in which they are wanting. Such, too, is the case in the
Guinea-Pig, in which I find the ducts proceeding in the
same manner from the nasal cavities, but terminating by
blind extremities in a prominent papilla placed behind the
superior cutting-teeth ;* an appearance the more unex-
pected, as the openings are very large in other Rodentia,
where, in the Hare for instance, they present themselves as
two oblique fissures behind the superior incisors, and in the
Rat as two minute openings placed on a projecting papilla.
In Man, too, this connection between the cavities of the
nose and mouth, appears to be wanting in the normal state,
in which respect we find a repetition of an earlier forma-
tion. This opening is altogether wanting in the Cetacea.

§. 642. Besides the mucous cavities of the nares, we
find also many smaller secreting organs dispersed over the
surface of the membranes of the continuations of the ali-

• Emmert has remarked the same fact in the Dromedary. Salzburg. Met3.
ZeU. No. 35. 1817. s. 160.

221

raentary canal ; among these we may class the glands of the
oesophagus, of the crop, of the cardiac sac of the stomach
in so many animals, and also those which secrete the
gastric juice, — a fluid that presents the character of the
saliva, though in a much more elevated degree. An
extended description of all these parts in the different
Classes of Animals will, however, be the less requisite, as,
on the one hand, they form an object rather of physiologi-
cal than of anatomical investigation, and, as on the other,
the most important parts have been already noticed in con-
nection with the description of the intestinal canal. The
latter remark is likewise applicable to those secreting
organs which present themselves in the lower part of the
intestinal canal, and with a peculiarly great developement
at the termination of the Rectum. We may, therefore,
next turn our attention to two other and larger secreting
organs, — the Liver and Pancreas ; of which the former is
so absolutely a repetition of the organs of respiration, that
we ordinarily find the degree of its developement in an
inverse ratio to that of those organs themselves. Hepatic
organs, too, appear to be so essential to the animal frame,
that we invariably find them even in the lower grades of
organization, though it is only in the superior forms that
they are still farther advanced by the super-addition of
another preparatory organ, the Spleen. This is not the
casfc with the Pancreas, which is much more frequently
wanting.

222

Section III. Of the Organs secreting Bile.

A. In Animals without Vertebra \

1. In Zoophytes.

§. 643. Organs which appear to serve the purpose of
secreting a biliary fluid have hitherto been observed in
but few species, and those only the higher ones, viz. the
Echinodermata, which have lately been separated from this
Class : in the inferior species, on the contrary, e. g. in the
Medusae, there is but a single and simple secretion into the
cavity of the stomach, combining in itself the characters at
once of saliva, gastric juice, and bile. This primitive iden-
tity of these secretions appears to be indicated also in the
Echinodermata, and even, as we shall And, in many of the
Mollusca, by the fact of the bile being poured immediately
into the stomach itself. In the Echinodermata, e. g. in the
Asterias, the hepatic organ appears to be represented by
a double row of little lobes placed in each of the five rays,
and from which a canal runs to the stomach. (Tab. J. fig:
XI. B.) Of the same nature probably is the flocculent
tissue which surrounds the Intestine of the Holothurise.

2. In Mollusca.

§. 644. In the Acephala the liver is placed in the same
manner close around the stomach or intestine, and fre-

223

quently is so little separable from those organs, that they
appear as though excavated out of its substance. This, for
instance, as already remarked, (§. 437.) is the case with
the liver of the Bivalves, the secretions from which are
poured into the stomach through several tolerably capa-
cious openings or ducts. (Tab. II. fig. IX. b. a.) Such,
likewise, is the disposition of the liver of the Ascidise,
(Tab. II. fig. II. g. g.) where it surrounds the convolu-
tions of the intestine in the same manner ; though, as I had
an opportunity of observing in a large species,* the intes-
tinal canal in young individuals is unattached, and a true
liver altogether wanting. In the Terebratulaeand Lingulae,
on the contrary, the liver, according to Cuvier, is more
distinct from the stomach, and in an equal degree more
closely connected with the intestine.

§. 645. In the Gasteropoda we find the liver of very
considerable size, divided into several lobes, and more
completely separated from the intestinal canal. Thus,
in the Helix pomatia , with which most other Shell-Snails
agree in this point, the liver occupies all the upper convo-
lutions of the shell, (Tab. III. fig. I. II. s. fig. III. o.)
has several turns of the intestinal canal upon its upper sur-
face, and pours its secretion, by means of two ducts, into
a ccecal expansion at the extremity of the stomach. In the
Aplysia, (Tab. III. fig. VII. n.) and nearly in the same
manner also in Slugs, it fills a great part of the common
muscular abdominal sac, and has several convolutions of the
intestinal canal wound about it. In the Genera Clio and
Doris, on the contrary, as is usual in the Acephala, it sur-
rounds the stomach, pouring the bile into it by several
openings. It is remarkable, too, that according to Cuvier’s
observations, a distinct excretory duct proceeds in the Doris
direct from the liver to the anus, which, taken together
* Mf.ckei.’s Archiv. f Physiol b. ii. h. 4.

224

with a similar organization in the Cephalopoda, appears to
prove that with such an extraordinary developement of the
liver the secretion is frequently more copious than is neces-
sary for the purposes of digestion, and, consequently,
that the excess must be rejected as excrementitious matter.

§. 646. The Cephalopoda also possess a liver of con-
siderable size: in the Sepia octopodia I find it forming an
oval yellowish body, placed in the upper and posterior part
of the abdominal cavity, enclosed within a continuation of
the peritoneum, (Tab. IV. fig. II. r.) and pouring the bile
by an excretory duct (n.) into the spiral-shaped coecum.
On its external surface, though still covered by the peri-
toneum, is the ink-bag before (§. 442.) mentioned; which,
though it probably secretes its own contents, and conse-
quently has a different relation to the liver from that of the
gall-bladder, in Man for instance, yet being evidently
supplied with vessels, and consequently with the materials,
for secretion by the liver, must clearly serve the purpose,
like the structure already noticed in the Doris, (§. 645.) of
evacuating a portion of the materials prepared by that
organ. It is disposed in the same manner in the Calmar; in
the common Cuttle-Fish (Sepia officinalis ), on the contrary,
the liver, called by the old anatomists Mutis, is placed
higher in the upper part of the body, pretty close behind
the infundibulum, (§. 442.) is attached more firmly to the
dorsal surface, and provided with two excretory ducts. The
ink-bag, as has also been already remarked, is situated at a
considerable distance from it in the lower part of the
abdomen.

225

3. In the Articulata.

§. 6 T7. The developement of the biliary organs, which
advanced so much in the preceding Class, recedes in an
equal degree in this, where the great object appears to be
rather the developement of the external form. In Vermes
a biliary organ is either altogether wanting, e. g. in the
Intestinal Worms, or it presents itself merely as a thin
punctiform coating, usually of a yellow or blackish colour,
on the external surface of the intestine, without any distinct
ducts for the conveyance of bile being perceptible. For
instance, there is a yellow layer of this kind around the
intestinal canal of the Dew-Worm, (Lumbricus terrestris ,
Tab. V. fig. III. 1.) and also of the Lug-Worm, (Lum-
bricus marinus .) In the Leech, on the contrary, the external
surface of the stomach is covered by a blackish mucous tissue.
The biliary organs are more distinctly developed in the
Crustacea : in Cray-Fish and Crabs we find them as large
bunches of yellow ccecal vessels, occupying the greater
part of the abdominal cavity, placed near the commence-
ment of the intestine, and pouring a bitter tasted bile into
its cavity. (Tab. VI. fig. IV. m fig. IX. e.) In the Squillse,
on the contrary, according to Cuvier, there is a true liver
divided into several lobes, and accompanying the intestine
on both sides throughout its course.

§. 64S. Lastly, in Insects the organs which analogy
leads us to suppose are intended for the preparation of bile,
in some degree assume such a diversity in their form as to
have created many doubts as to their true character.* Many

• The deviation in the evolution of the biliary organs coincides in this
instance as perfectly with the extraordinary developement of the respiratory
organs, us the perfect formation of the liver in the Mollusca with their bran-,
chial respiration. (§. 64-2.)

VOL. II.

22 6

contradictions, however, may be reconciled by the follow-
ing view. The function of the liver as a secreting organ
differs from the secretory action of the lungs in this
respect, that the latter expels carbonaceous matter in a
gaseous state, and the former a similar matter (though at
the same time abounding in hydrogen and azote) in a more
solid form. The deposition of fat coincides . in many respects
with the secretion of bile — a fluid abounding in adipose
and resinous elements — from the liver; and if the bile, as
an essential requisite to digestion, has a direct influence on
nutrition, so also does the fat indirectly contribute to the
same end, as a deposit of pure nutritive matter. Hence
the deposition of fat and the formation of a liver appear to
be less completely ’separate in the inferior Classes ; hence,
too, we can more readily understand the bulk of the liver
in the Mollusca, inasmuch as in them that organ probably
forms at the same time a deposit of nutritive matter : and
even in the higher Classes of Animals we shall, for the
same reason, find the liver occasionally distinguished by the
quantity of fat it contains. These functions and structures
necessarily appear more completely separate in Insects, the
greater part of which want a true vascular system. In
them the secretion of peculiar materials, as has been already
noticed with regard to the saliva, venom, the liquids em-
ployed in spinning, & c. being performed not by glands,
but merely by vessels with closed extremities, it follows that
the bile must be prepared in the same manner by similar
vessels, and the lirer, as a biliary organ, replaced by biliary
vessels; whilst, on the contrary, the deposition of pure
adipose nutritive matter is connected with another struc-
ture,— the liver, in so far as it is a depot of that kind, being
represented by the adipose bodies which have been already
noticed (§. 453, 458.) ; a suggestion by no means weak-
ened, if it should be found that the biliary vessels derive

227

tlie materials for their secretion from the adipose bodies, a3
a general depot of nutritive matter, from which, also, other
parts are supplied with their component elements. It com-
pletely coincides, likewise, with this view, that in those
Insects which approximate to the Crustacea, and present a
true vascular system, the character of liver and of adipose
bodies is more perfectly united in a single organ. This
appears to be the case in Spiders, where the adipose bodies
(Tab. VII. fig. I. d.) adhere so closely to the stomach
that it is as impossible to separate them anatomically
as to detach the liver from the parietes of the stomach in
the Bivalves ; and where, also, not only chyle is deposited,
but likewise a secretion of bile takes place, as is proved
by the brown colour of the excrements* in the portion of
intestine that follows. It is remarkable, however, that here
also there are, in addition, peculiar biliary vessels, which
pour out their contents about the anus, (fig. I. e. e. e. e.)
and, consequently, inasmuch as they appear merely to eva-
cuate superfluous materials, remind us of the similar orga-
nization before noticed in some Gasteropoda and Cephalo-
poda. (§. 645, 646.) There is something similar, also, in
the Scorpion, though in it the fatty body is more perfectly
distinct from the intestine, and disposed along each side of
it; (Tab. VII. fig. IX. g. g.) there are moreover, however,
according to Treviranus,! peculiar biliary vessels (f. f.)
on each side, which, probably arising from the fatty body,
absorb from it the biliary fluid that they pour into the
intestine.

§• 649- In the remaining Insects, where it is impossible
to detect a true vascular system, the evident relation exist-
ing between the fatty bodies and the secretion of bile
disappears ; the biliary vessels, on the contrary, being much
more completely developed than, for instance, in the Scor-
* Uebcr den Ban dcr Arachnidm, s. 32. f Loc. citat. p. G.

Q 2

228

pion. They exist as well in the larva as in the perfect?
Insect, though there are sufficient points of difference cor-
responding to those different stages of developement ; thus,
in the Caterpillar, in accordance with the extraordinary
size of the intestinal canal, the biliary vessels are much more
considerable than in the Butterfly. The form, number, and
attachments of these biliary vessels;, called by the older
anatomists Vasa varicosa, are extremely various in these
animals. As to form, they are most commonly simple
capillary threads, but occasionally also irregular, and beset
with little blind pouches, as I have distinctly observed in the'
Caterpillar of the Sphinx Euphorbise: (Tab. VII. fig. XII.
e. e.) Their length, as Cuvier also states, is usually in
an inverse ratio to their number ; thus, in the same Cater-
pillar they are long, (fig. XI. f.) and in the Cockroach,
(fig. XX. k.) on the contrary, short. Their number,
according to Rajvtdohr,* reaches, and always in even
numbers, to as many as 150. They are very numerous
in some Neuroptera, e. g. the Libellulre, in the Orthoptera,
e. g. the Cockroach, (fig. XX. k.) and in the Mole-Cricket
(Gryllus gryllotalpa), where they all unite, like a tuft,
into one trunk previous to being inserted into the Intestine.
In the Coleoptera there are two, in Caterpillars and But-
terflies three, on each side, which, uniting into a common
trunk, open on each side of the intestine. (Tab. VII. fig.
XII.) The mode in which these vessels terminate is yet
but imperfectly known, for, according to Ramdohr, they
appear to open between the coats of the intestine without
perforating the internal membrane. They usually enter
the intestine at its commencement, immediately below the
pylorus, though that point varies according to the extent
allowed to the stomach: in the Onisci, according to Cuvier,
they enter close to the oesophagus. According to Ramdohr,.

* Ueber die Verdauungswerkzeuge dcr Inschtcn. Halle, 1810.

229

they are also connected in the Coleoptera and some
Caterpillars with the coecum or rectum : in the Aclieta,
Locusta, and Buprestis, Meckel* states that they pene-
trate the intestine in two different points ; whence we may
conclude, that, as in certain Mollusca, a part of their
secretion serves to assist in the digestive function, whilst
die remainder is a purely excrementitious product.

B. Biliary Organs in Vertebral Animals.

§. 650. In all of the four Classes belonging to this
division there is a perfectly formed liver, the only essential
difference between which and the liver of the Mollusca

is, that it does not receive the blood necessary for its secre-
tion, like every other secreting organ, and as in the inferior
Classes, from the principal artery of the body only ; but
that it is farther supplied by a particular venous system,
(the Vena Portae,) hereafter to be considered. There is
besides in these Classes another peculiar organ, connected
with the liver by the mode in which the blood is distributed,
viz. the Spleen ; which we may, without any impropriety,
consider as taking a part in the secretion of bile, were it
or^ly as being the means of converting a greater quantity
of arterial into venous blood, and may in consequence
examine it at the same time with the liver, as being, like

it, a preparatory organ ; an opinion with which it perfectly
coincides, that we observe the developement of the two
organs proceeding in an inverse ratio, the spleen being-
smaller in proportion as the liver is large and perfectly
formed. With regard to the liver itself, it is to be remarked,

* Translation of Cuvier’s Corny. Anat. vol. iii. p. 713.

230

that in the superior Classes it presents a peculiar recep-
tacle for bile, (the gall-bladder,) which may, to a certain
extent, be viewed as a repetition of the ink-bag of the
Sepiae, as the fluids subservient to the secretion of the
latter organ are furnished to it by the liver, and as also, in
certain Mammalia for instance, ducts are found conveying
the hepatic bile direct into the body of the gall-bladder :
on tbe other hand, the two organs offer some important
differences, inasmuch as the fluids contained in the ink-bag:
appear to be purely excrementitious, and are probably
secreted from the coats of the bag itself; whilst, on the
contrary, no such secretion takes place in the gall-bladder,
and its contents are evidently important aids to digestion.

1. Biliary Organs in Fishes.

§. 651. The great extent of the liver in this Class
must be considered as a very positive approximation to the
organization of the Mollusca, as well as a result of the
existence of branchial respiration, the developement of the
respiratory organs and of the liver usually proceeding in an
inverse ratio : (§. 642.) nor is it less remarkable in another
point of view, (§. 648.) that, as Blumenbach* lias shewn,
the liver of several Fishes, e. g. the Ray and Cod, which
are otherwise almost wholly without fat, teems with oil.
As to the size and shape of the liver, the former is usually
so considerable as to occupy a large portion of the abdomen,
(Tab. IX. fig. XVIII. g.) several convolutions of the
intestine, precisely as in the Mollusca, being frequently
* Ilandbuch der Verglcich. Anal. s. 184.

231

enclosed within it, particularly in the Genus Cyprinus.
The shape presents many varieties in the different Genera :
it is usually adapted to the form of the abdomen, present-
ing a longitudinal mass, convex superiorly, concave infe-
riorly ; (fig. XVIII. XIX.) sometimes, as in Lampreys,
the Trout, and Pike, simple and undivided; at others,
divided by fissures into several lobes, e. g. into three large
ones in the Burbot, into very many distinct lobes in the
Carp; in the Electric Ray, &c. into two large and almost
completely separate halves, each of which is composed of a
small and of a large oblong lobe.

§. 052. The colour of the liver is commonly yellowish,
reddish, or brownish. The grass-green colour of the liver
in the Lampreys (in the Petromyzon brancliialis I find it
orange,) is remarkable, particularly because here, and also,
according to Cuvier, in the Nile Perch, Plaice, some
Scisense, &c. the gall-bladder is wanting,* which otherwise
exists almost universally throughout this Class, and in struc-
ture as well as position varies but slightly from that of Man.
(Fig. XIX. s.) There are usually several biliary ducts,
which, as Cuvier has observed, for the most part enter the
gall-bladder or its excretory duct at an obtuse angle, thus
facilitating the entrance of the usually bright green bile
into that organ, whence it is conveyed into the intestine by
the cystic duct. In the Turbot (Pleuronectes maximus)
th^fe is farther a peculiar expansion of that canal before
it opens into the intestine ; whilst in the Basking-Shark
(Squalus maximus ), according to Home, its aperture projects
in the form of a long papilla into the dilated part of the
intestine immediately below the pylorus.f

* In the Lamprey, however, the deficiency is supplied by a tolerably large
dilatation of the biliary duct.

f I find a similar structure at the orifice of the biliary duct in the Stur-
geon.

232

§. 653. The Spleen in Fishes is singularly small as
vmpared with the Liver, and at the same time of a much
brighter colour than in Man. Its shape is sometimes glo-
bular, (Tab. IX. lig. XVIII. i.) ; at others, oblong,
angular, or irregular : it is situated at the great end of the
Stomach in the Shark, and in some other species, e. g. the
Trout, in which, as well as in the Sturgeon, its size is con-
siderable, that of the Liver being moderate. In other
instances, on the contrary, it is placed more in the vicinity
of the Intestine, and between the laminae of the Mesentery,
e. g. in the Burbot. (See Tab. IX.) It appears to me to
be altogether wanting in the Lampreys.

2. Biliary Organs in the Amphibia.

§. 664. The size of the Liver is also very considerable
in this Class, and its colour not much darker than in the
preceding Class. In the Salamander, it extends from the
Heart, between and in front of the Lungs, as far as the
great end of the Stomach, which it almost wholly covers ;
and is attached, on its anterior surface, by a Ligamentum
suspensorium derived from the anterior peritoneal covering
of the walls of the abdomen. (Tab. XIII. fig. III. f.)
It is bi-lobate at its inferior edge, where, also, on the
concave surface we find a Gall-bladder (fig. IV. 1.) filled
with green Bile, and having its Ducts disposed in the usual
manner. The Spleen is small, oblong, of a bright colour,
and attached to the left side of the Stomach. (Fig. III. g.)
In the Proteus, the entire length of the animal being only
from 9 to 13 inches, that of the Liver, which is divided
into five lobes, is 5 inches; there is, likewise, a Gall-bladder

233

ef tolerably large size. The disposition of the Liver, Gall-
bladder, and Spleen, is pretty nearly similar in Frogs and
Toads; except that the former is wider and more absolutely
divided into two lobes, having the Heart placed between
them in front ; the Spleen, on the contrary, is smaller,
farther removed from the Stomach, and in an equal degree
approximated to the Colon. In Tortoises, the Liver is
almost completely divided into two portions; its colour,
according to Meckel’s remark,* being usually blueish-
green, and the right lobe much larger than the left.f The
latter point I find confirmed in the Mud-Tortoise, where,
however, the colour is usually yellowish«brown.

§. 655. In Serpents, the length of the Liver is ■ very
great as compared to its breadth (e. g. in the Coluber natrix ,
32 inches long, its length was 6^ inches, its breadth about
half an inch) : it consists, also, like the similarly elongated
Lung, of only one lobe.J The hepatic duct is very long

* Translation of Cuvier’s Comp. Anat. vol. iii. p. 572.

f This increase of the volume of the right lobe of the Liver, peculiar to
so many animals, and even to Man himself, has an evident analogy with the
preponderance of respiration on the right side, and the greater size of the
right Lung.

\ Several investigations lead me to think that the formation of the Liver
is determined as absolutely by the distribution of the Umbilical Vein, as that
of th^ Pancreas, and probably, also, of the Spleen, by the course of the
Omphalo-mesenteric Vein : hence, consequently, the Liver is so long in
Serpents because of the extent of the course of the Umbilical Vein from
the Umbilicus to the Heart ; whilst the Pancreas is so small on account of
the short space from the same point to the posterior part of the abdomen.
Hence, too, we observe a very long Pancreas in Birds, because the Omphalo-
mesenteric Vein runs in the middle of the first long convolution of Intestine,
which space is afterwards completely occupied by the Pancreas ; whilst, on
the contrary, the Liver is wider than it is long, because the course of the
Umbilical Vein is here so much shortened. Nay, it is remarkable, how the
Vena Umbilicalis, belonging chiefly to the almost branchial Respiration of

and slender, and is connected in tlie vicinity of the com-
mencement of the Intestinal Canal with the cystic duct,
which then perforates the Pancreas. The oval Gall-bladder
is at a considerable distance from the Liver, and contains a
brownish-green Bile. The Spleen is small, globular, and
placed at the upper extremity of the Pancreas. In Lizards,
again, the Liver is more similar to that of the Frog and
Salamander : in the Gecko I find it elongated, divided by
a longitudinal groove into two larger portions, narrow above
and broad below, (almost like a jJ; in the Crocodile, on
the contrary, it is more similar to that of Man, (Tab. XII.
fig. XIX. 1.) and has in the same manner the Gall-bladder
placed on its concave surface (n.). According to Cuviek,
the hepatic and cystic ducts enter the Intestine, sometimes
together, sometimes separately. The Spleen forms a little
oblong body at the great end of the Stomach, (g.)

3. Biliary Organs in Birds.

§. 656. Here, likewise, the Liver is proportionally
larger than in Man and Mammalia; at the same time being
of a more brilliant red colour, and, like the Liver of several
Lizards and Tortoises, divided into two principal lobes, a
right larger, and a left smaller, between which the Heart
projects from above. (Tab. XV. fig. XL i. h.) Iiede-

the Embryo, appears to form the lung-like excretory organ, the Liver;
whilst, on the contrary, the Omphalo-mesenteric Vein, belonging to the ex-
ternal organ of nutrition, the Vesicula Umbilicalis, gives rise to the organ
which secretes the milk-like Pancreatic Juice. I reserve a more extended
investigation and exposition of these points for another opportunity.

'235

MANNf has given an interesting tabular view of the diffe-
rences of size of the Liver in different Birds, from which
it appears that its bulk is greatest in Aquatic and Wading
Birds, viz. from T\j to ^ of the weight of the body ; and
smallest in accipitrine Birds, viz. from -j to of the
weight of the body. Anteriorly it is covered by the
Sternum : the lungs stretch down behind it on the dorsal
side, whilst it is retained in its place by the parietes of the
air-cells, and covered by their continuations. There are
not any very essential variations in the form of the lobes in
the different species. The biliary ducts arise from the under
concave surface of the organ, one or more of them usually
opening into the fundus of the gall-bladder, which, how-
ever, is not uniformly present, I myself having found it
wanting in the Parrot and Dove, and others, at least in
some instances, in the Guinea-fowl, Grouse, Ostrich, and
Peacock. The hepatic as well as the cystic duct, here
usually enter the Duodenum at a distance from the Pylorus,
(Tab. XV. fig. XII. i.*) close to the Pancreatic duct, an
arrangement dependent on the long loop formed by that
Intestine, which almost returns to the Stomach. As to the
Spleen, it is extremely small, usually globular, of a dusky
colour, and connected rather with the glandular cardiac
cavity and left portion of the Liver than with the Gizzard.
(Tab. XV. fig. XII.)

t Zoolngie, b. ii. s. 4-91. The increased size of the Liver, and its con-
version into a fatty substance, in several domesticated birds is very remark-
able as an effect of abundant nutrition and limitation of muscular motion.

i. Biliary Organs in Mammalia .

§. 657. In the same maimer as in the inferior Classes
of Animals, the Liver was particularly large in proportion
to the Spleen and to the whole body; the Spleen in the
Mollusca being even wanting, though the Liver exists in
great perfection; so also, in the history of the developement
of Mammalia, and even of Man himself, we observe a
similar proportion, corresponding to the less perfect degree
of developement of the respiratory organs; the mass of the
Liver being comparatively much smaller at a subsequent
period, when the formation of the body is completed. So,
likewise, those Species, e. g. the Whale and Porpoise,
which approximate in several respects to Fishes and to the
foetal state of the more perfect Mammalia, are distinguished
by the size of the Liver and the smallness of the Spleen.*
In them the Gall-bladder is wanting, though in point of
shape the Liver, according to Hunter, -f is pretty similar
to that of Man, being like it divided into a right larger
and left smaller lobes, and furnished with a round and
suspensory ligaments. The biliary duct is capacious, and
enters the commencement of the Duodenum. The small
spherical Spleen is sometimes, according to Hunter,
double in the Porpoise; nay, according to Tyson, divided
info ten or twelve portions.

§. C58. The Manati approximates to the Cetacea by
the very large size of its Liver, which is divided only into

* Lacdpcde Histoire Nat. des Cctacees, p. 3G : “ La baleine Tranche a une
foie ties volumineux, une rate pen etenilue.”

f Philos. Trans. 1787. p. 410.

two principal lobes, as well as by tlie deficiency of the
<jrall-bladder;f forming in these respects a transition to the
hoofed animals, in which the Liver, though somewhat
smaller, ordinarily presents the same form, and where also
the Gall-bladder is usually wanting, e. <7. in the Solipeda
and Deer, and, according to Cuvier, in the Camel, Pec-
cary, Elephant, Rhinoceros, and Daman, In the Seal, 011
the contrary, the Liver, though still large, is divided into
several lobes, — according to Albers, into 7; the Gall-
bladder is present, and the same general disposition is com-
mon to most of the remaining Mammalia,;): particularly the
Carnivora and Rodentia. (See the Liver of the Beaver,
Tab. XIX. fig. XIV. u.) We are again indebted to
TiedEmann* for a tabular view of the size of the Liver
in several Carnivora and Rodentia, from which it appears
that it is very considerable in those species which burrow
or dive. He found it, for instance, in the Dog yy, in the
Fox and in the Hare of the weight of the body ;
whilst, on the other hand, it was Ty in the Field-Mouse,
and yy in the Marmot and Otter.

§. 659. The Gall-bladder is wanting, however, in several
Rodentia, e. g. in Mice, in the Hystrix dorsata, and in
the Hamster. It deserves, however, to be remarked of
the hepatic ducts, that when the Gall-bladder is wanting,
their common trunk is considerably dilated, thus, e. g. in
the /Elephant and Horse, compensating the deficiency.
In the Otter, however, according to Daubenton, this
dilatation in the vicinity of the Duodenum is coupled
with the existence of a gall-bladder. Lastly, the direct

f Tiedemann, Zoologie, b. i. s. 546.

\ Haller ( Elew . Phys. t. vi. p. 462.) says, “ Animalibus quadrupe-
“ dibus, quibus divisi sunt pedes, plerisque etiam hepar in multos lobos
“ dividitur.”

* Zoologic, b. ii. s. 522.

23S

hepato-cystic ducts, which are found, for instance, in the
Ox and Sheep,* and which, as was also the case in several
Birds, convey the bile immediately from the liver to the
fundus of the gall-bladder, are in many respects remarkable;
particularly as reminding us of the relation of the ink-bag
to the liver in several Mollusca, (§. 644.) in which that
bag, though unconnected with the biliary ducts, received
all the materials for its secretion from the vascular texture
of the liver. The spleen of Cetacea has been already
noticed ; in other Mammalia it is usually elongated, tongue-
shaped, ( e . g. in the Beaver, Tab. XIX. fig. XIV. z.) and
comparatively much smaller, though at the same time of a
brighter colour, than in Man. Its position is invariably at
the left side of the great end of the stomach, and when
there are several stomachs, at the left side of the first or
larger one.f

Section IV. Of the Pancreas.

§. 660. We have already seen some instances among
the proper salivary organs of the Mollusca, in which they
were partly situated in the region of the stomach: as, for
instance, the salivary glands extending into the cavity of the
abdomen of the Aplysise, and the second pair of salivary
glands in the Sepise ; and, consequently, when we find a
peculiar organ in the same situation in the higher Classes
resembling the salivary organs, we may to a certain extent

* See the various observations of Haller on these hepato-cystic ducts
in his Elem. Physiol, t. vi. p. 535.

f In the Walrus the bile passing from the liver enters into the upper ami
lateral part of a large oval cavity with very thick coats, terminating in a canal,
which, for some distance before it penetrates the parietes of the intestine,
runs behind the duodenum in the form of a thick cylindrical mass. (Home,
Phil. Trans. 1824, p. ii. 233.) — Translator.

239

view it as a repetition of the earlier type. Those deep-
seated salivary glands are, however, by no means identical
with the pancreas of the higher animals, inasmuch as they
pour their fluid into the commencement of the alimentary
canal, whilst the secretion of the latter appears to be more
intimately connected with the preparation of bile, or at
least to act upon the alimentary pulp in combination with
the biliary fluid. Hence we must consider those secretions
alone as perfectly analogous to the pancreatic fluid of the
inferior species of animals which are actually poured into
the beginning of the intestine, properly so called, and
which, as we have already pointed out, are furnished by
certain ccecal pouches around the parietes ot the intestine
in that situation. Hence, also, the first indication of the
existence of true pancreatic organs probably presents itself
in the form of a circle of little coeca in the Holothuriae,
(§. 434.) similar cceca occurring in the region of the pylorus
in the Aplysise, (§. 440.) Cephalopoda, (§. 441, 442.)
Worms, (§. 445.) and Insects, as substitutes for the pan-
creas ; until at length in certain Fishes these coecal appen-
dages become more numerous, (§. 471.) and finally, as in
the Sturgeon, are consolidated into a single apparently
glandular mass. A genuine pancreas, however, coinciding
essentially with the structure of that of Man, appears to
exist only in the three superior Classes of Animals.* f

* According to Cuvier, indeed, Sharks and Rays possess a pancreas-like
organ of gelatinous consistence, divided into several lobes, and opening by
some ducts into the intestine : its true nature, however, requires farther
investigation ; as is also the case in some other Fishes which are said to
possess a pancreas. (See Haller’s Elein. Pb/sioL t. vi. p. 427, 436.)

f In the Loligo sagillata there are two glands at the lower and front part of
the liver, consisting of numerous lobes of a rose-red colour, and which have
sometimes been considered as an ovarium. They surround the two biliary
canals in their course from the liver to the spiral stomach, and communicate
with them by numerous small ducts. They exist in an equally developed
state in both male and female, and have not any organic connections with

240

1 . Of the Pancreas in Amphibia.

§• 661. It usually exists here as a smooth, glandular
mass, divided into irregular lobes, and placed between the"
layers of the mesentery at the first curve of the intestine?
so, at least, I find it, for instance, in the Frog, the Mud-
Tortoise, where it is of considerable size, and in a young
Crocodile. On the contrary, in the Coluber natrix and
Spotted Viper I find it forming a denser mass, placed more
forwards on the intestinal canal, and perforated through its
centre by the biliary ducts. In the Crocodile of the Nile
Cuvier found the excretory ducts double.

2. Of the Pancreas in Birds.

§. 662. As this gland in Birds usually occupies the space
between the two portions of the first, and generally very
long, fold of intestine, its size is commonly larger in pro-
portion than in any other Class of Animals. Tiedemann*
found it very large in those Birds that live on vegetables,
and, on the contrary, smaller in rapacious Birds; with
which my own observations agree: Its form, which is regu-
lated by its position between the two portions of the first
fold of intestine, is usually long, narrow, and flat. (See it
in the Dove, Tab. XV. fig. XII. k.; and on the probable

the sexual organs. Injections into the alimentary canal pass from the- spiral
stomach into the ducts, connecting these glands with the biliary canals. Dr.
Grant, by whom they are thus described, considers them as corresponding
to the conglomerated pancreas of the Chondropterygious Fishes. ( Edin .
Phil. Journ. xiii. 198.) — Translator.

* Zoologie, b. ii. s. 475. Is it not probable that its size corresponds to-
the great magnitude of the vesicula umbilicalis in this Class ? (Compare
the Note to §. C55.)

241

cause of its form, and of the origin of the organ generally,
see the Note to §. 655.) It is generally divided into two
perfectly distinct lobes, e. g . in the Magpie, Parrot, Goat-
sucker, &c. ; more rarely — as in the Ardea pavonica , and
some individuals of other species, in which it is properly
single — it is completely double ; in which case the addi-
tional gland is placed in the second loop of Intestine. The
pancreatic ducts in Birds* are from one to three in number,
and not always the same even in the same species, each
entering the Intestine separately, and usually before the
biliary ducts (fig. XII. 1.) : thus, according to a Table
given by Cuvier, in the little Owl (Strix passerina), the
Intestine is first perforated by three pancreatic ducts, then
by the hepatic duct, and, lastly, by the cystic duct; in the
Parrot the hepatic duct comes first, then the two pancreatic
ducts, and, lastly, the cystic duct ; in the Ostrich the hepatic
opens into the Intestine before the single pancreatic duct.

3. Of the Pancreas in Mammalia.

§. 063. Though the proper salivary glands are wanting
in several species of this Class, such is by no means the
case with the Pancreas, which is invariably found, and even
in the Cetacea, where, according to Hunter, it appears
as a very long flat body, the left extremity of which is
attached to the right end of the first stomach, and also to
the Duodenum, its excretory duct opening into the biliary
duct near the entrance of the latter into the intestine. In

* As is well known, (see Haller’s Elem. Physiol, t. vi. p. 434,) this
Duct, though already known to Galen, was discovered by Maur. Hoff-
mann, at Padua, in 1641, in the Turkey; and was then subsequently described
in Man by Wirsl’NG.

VOL. II.

242

tlie remaining- Mammalia its shape differs only from that
of the human Pancreas in being longer, and in being
frequently divided into several branches. (See that of the
Beaver, lab. XIX. fig. XIV. k. 1. m.) The excretory
duct is usually single, though double in the Elephant, and
very commonly opens into the Intestine at the same point
with the biliary ducts ; and particularly in the Ruminantia
and most Carnivora.

B. Repetition of the Respiratory Organs in the Sexual
System ; or , Of the Urinary Oi'gans.

§. 664. In the same manner that the Liver, as a secre-
tory organ connected with the intestinal canal, evidently
repeated the respiratory function, and consequently, as
regarded its developement, stood in an inverse proportion to
the respiratory organs, so, also, the urinary organs connected
with the sexual system present themselves in several re-
spects as absolute imitations of the respiratory apparatus,
and consequently, though they can be distinctly traced
only in the four superior Classes of Animals, are usually
larger in the inferior than in the superior of them. It is
particularly deserving, too, of notice, that from the consi-
deration of the foetal state of the superior Classes, we learn
that a part of the urinary apparatus itself, viz. the Bladder,
with its continuation, the Allantois, is actually a respiratory
organ, inasmuch as the vessels which perform the respiration
of the foetus are distributed either immediately upon its

243

membranes, or upon a membrane (the Chorion), conti-
nuous with it. The latter is particularly evident in the
embryo of Birds, in which the bladder, (Chorion or Allan-
tois,) continued from the Cloaca appears distinctly bran-
chial ; whilst, even in the human foetus, it is well known
that the Umbilical Arteries extend at the sides of the
Bladder and Urachus to the Chorion. Nay, we even find
animals where the Allantois (elongated Bladder) does not
protrude out of the abdominal cavity, but, nevertheless,
attains a considerable size that remains through life, and at
the same time continues to receive ramifications of vessels
similar to those which are else furnished in the foetus only
by the umbilical vessels.

§. 665. These precursory remarks were necessary, in
order more clearly to prove, that we are justified in view-
ing the Kidnies, and Urinary Bladder, as constituting an
evident repetition of the relation existing between Gills
and a Swimming Bladder ; for, as the blood is purified by
the former from superfluous carbon, so also are the Kidnies
destined for the evacuation of hydrogenous and oxygenous
elements : in the same manner, too, that we found that a
part of the materials taken in by the Gills (even pure
Oxygen, which is present in no inconsiderable quantity in
the Swim-bladder of many Fishes) is carried by the vascular
system into the Swim-bladder and accumulated there, so
also /the fluids poured out from the Kidnies (which, in the
former case, were gasiform) are here collected in the
Urinary Bladder: and, lastly, in the same manner that we
saw that the Swim-bladder did not uniformly occur in con-
nection with the Gills, so here we observe that the Urinary
Bladder is occasionally wanting, though the Kidnies are
invariably present.

I hough we above remarked, that true urinary organs
existed only in the higher Classes of Animals, the assertion

r 2

244

must not be taken as though all traces of them were want-
ing in animals without Brain or Spinal Marrow : on the
contrary, in examining the sexual organs, we shall have
occasion to observe that various secretory, nay even
respiratory, apparatuses are connected with them in the
lower gradations of the Animal Kingdom, having in them
nearly the same character as the urinary organs of the
higher Classes. But since in the four superior Classes,
also, peculiar secretions commonly occur about the Sexual
Organs, I deem it more advantageous to consider all the
organs subservient to such secretions in connection with the
sexual system: nay, even the description of the urinary
organs might have been deferred to the same opportunity,
were it not that they too completely form a distinct whole
in themselves, and, in consequence, exert too important an
influence on the whole animal ceconomy.

Section I. Of the Urinary Organs in Fishes.

§. 666. In the same manner as, from the branchial
respiration of these animals, the Liver was of striking ex-
tent, so also are the Kidnies, which extend as a single mass
along the spine at the posterior part of the abdominal
parietes, and occasionally occupy the whole extremity of
its cavity, e. g. in the Burbot (Tab. IX. fig. XIX. u.) :
sometimes appearing .merely as long narrow masses termi-
nating above and below, in rounded points, without reach-
ing the lower extremity of the abdomen, e. g. in the Trout:
or, again, are furnished with an appendix on each side,

845

whence the whole mass appears as an elongated cross, e. g*
in the Genus Cyprinus. They consist of a perfectly uni-
form mass comparable to that of the Spleen in Man, and
we find the branches of the Ureter arising by numerous
radicles, nearly in the same manner as those of the biliary
ducts from the substance of the Liver. The two Kidnies
of Fishes are so closely connected, that we may consider
them as forming a single mass, the separation between
them being indicated only by the existence of two Ureters
and the groove on their surface for lodging the Vena Cava.
Even the Ureters not infrequently, e. g. in the Trout, unite
soon after their commencement into a single trunk, and,
consequently, when we view the two halves of the Kidney
covered by the Peritoneum, we can scarcely recognise them
for any thing else than a single mass. We find the Kid-
nies, or rather Kidney, of Fishes immediately above or
behind the Swim-bladder, which is particularly remarkable
in those instances, as the Burbot and Trout, where the
latter is closely attached to the vertebral column. In Rays
and Sharks, the Species which are in so many respects the
highest of this Class, the Kidnies, according to Cuvier,
are proportionally smaller, a fact which I also have found
confirmed in the Electric Ray.

§. 667. As the Kidnies of Fishes usually extend to, or
evep beyond, the anus, the Ureters are ordinarily very
shoft, e. g. in the Carp, Pike, and Trout ; but immediately,
as already remarked in the Trout, unite into a single trunk,
which then expands into an oblong receptacle that can
scarcely be called a Bladder, and terminates in a conical
canal opening at the orifice of the sexual organs behind the
anus. On the contrary, I find a very considerable true
urinary Bladder in the Burbot, (Tab. IX. fig. XIX. m.)
which also, according to Cuvier, exists in the Lophius
piscatorius, Cyclopterus lumpus, and some other Cartilaginous

246

Fishes.* The Urinary Bladder is wanting in Rays and
Sharks, though, according to Home,-}- the Ureters open
into a dilatation which forms a heart-shaped projection be-
hind the anus, and which, as both semen and ova are there
evacuated, is to be considered in the male as a Penis, in
the female as a Clitoris. (Tab. X. fig. II. 1.) In the
Lampreys, also, I find a similar conical projection corres-
ponding to the openings of the sexual and urinary passages.
There are in this Class no traces of Renal Capsules, nor
of the perfect internal organization of the Ividnies them-
selves, which we find in Man, for instance.

Section II. Gf the Urinary Organs in the Amphibia ,

* >

§. f>68. In this Class the mass of the Kidnies is more
evidently divided into two portions, and their size, though
much diminished as compared with Fishes, still very consi-
derable : thus, in the Salamander, they extend through
nearly one half, and in the Frog nearly one third, of the
length of the cavity of the trunk. According to the differ-
ent Orders, there are many varieties in their form and
position. In the Salamander, they agree very closely with
those of Fishes, are elongated, very narrow, extend low

* A satisfactory idea of the causes on which depends the absence or
presence of the Urinary Bladder in Fishes, can only be expected from a more
perfect acquaintance with the external organs accessory to the developemeut
of the Foetus in this Class.

f See his Essay on (he Generation «f Sharks in the rhilosoph. Transact.
1810. p. 20.5.

21.7

into the Pelvis, and are thickest at their inferior extremi-
ties. (Tab. XIII. fig’. III. i.) The shape of the organs
described as Kidnies is the same in the Proteus.* In the
Frog, they are placed somewhat higher ; are shorter and
broader, but still very closely approximated. In the Mud-
Tortoise, they are rather oval, and have lobes, which appear
upon their surface nearly like cerebral convolutions. In
Serpents, particularly the Coluber natrix and Spotted Viper,
I find them elongated, consisting very evidently of indi-
vidual sections arranged in a series, tolerably broad above,
and extending higher on the right than on the left side.
In Lizards, they are nearly the same as in Frogs ; though
in a young Crocodile, about 18 inches long, I find them
divided into lobes similar to, though less distinct than,
those of Serpents.f (Tab. XII. fig. XIX. v.)

§. 669. The Ureters, which in Frogs, Salamanders,
and Lizards, are short, in Serpents, on the contrary, of
considerable length, arise here, as in the preceding* Class,
by minute radicles from the substance of the Kidney, which
unite into one trunk, and open into the Cloaca, in Frogs
in connection with the seminal vessels. In several Am-
phibia, however, the Bladder is very remarkable, which in
Frogs is but intermediately connected with the Ureters,
arising from the front part of the Cloaca, whilst the Ureters
open into it posteriorly. There are Bladders of this kind
in/the two first Orders of this Class, in Frogs, Salamanders,
and 'l ortoises, and of very great extent as compared to
the size of the animals. In the Salamander, for instance,
the two portions of the Bladder, when distended with air,

* Schreibers in the Pldhsoph. Transact. 1801, p. 253.

f Cuvier ( Comp . Anat. vol. iv. p. 030,) thinks that he has observed,
that the lobes of the Kidnies are more distinct in old than in youn^
Crocodiles.

248

equal two-thirds of the size of the trunk: Townson*
observed that in the Tree-Frog the contents of this Bladder
equalled one-fourth of the weight of the animal; and quotes
Perrault, who found it containing more than 12 pints of
limpid fluid in a large Land-Tortoise. Its shape is not
always the same ; but commonly, as in Frogs, the Sala-
mander (Tab. XIII. fig. III. m.), and several Tortoises,
it is provided with two lateral cornua rounded at the angles,
and which appear to form a repetition of the vesicular
dilatation of the Oviduct ot served at the same point in
Frogs more particularly. Among the remaining Orders,
according to Cuvier, the Iguanas, Monitors, Chameleons,
Flying Lizards, &c. ; and also, according to Emmert and
Hochstetter,-}- the common Lizard (L. agilis ) and Slow-
worm, though in a less degree, are provided with a similar
prgan; whilst, on the contrary, it is apparently wanting in
the remaining species, and particularly in Serpents.:}:

§. 670. I have drawn very interesting conclusions as to
the true nature of this organ from the observation of the
progress of the developement of Frogs and Salamanders, of
which I will here mention the most essential only. If we
examine the Ovum of the Salamander (Lacerta salamandra) y
we find the foetus unattached within it, and without any
umbilical cord; consequently, the parts which in the higher
Classes of Animals we consider as external organs for the

* Tracts and Observations in Natural History , p. 65.
f Reil’s Archiv. b. x. s. 114.

| In Crocodiles, the Ureters are short, capacious, and with very thick
coats, penetrating the upper side of the Cloaca at a considerable distance
from each other. In the Chelonia, they terminate in the urethra, and,
therefore, communicate indirectly only with the bladder, a circumstance
which may, perhaps, afford an additional argument in favour of the idea that
pie function of that organ in thbsc animals is not as a receptacle of urine,
(see §. 671.) (CuviEii, Coni]). Anal. v. 233.) — Translator.

249

t!eveloperaent of the foetus, must here be included within
the embryo itself at a very early period. The Vesicula
Umbilicalis is therefore inclosed within the abdomen, as is,
also, the Allantois, which, however, appears merely as a
urinary Bladder, not being perceptible externally to the
embryo ; whilst, on the contrary, in the foetus of Lizards
and Birds it is extruded with the character of branchiae,
but subsequently fades away, leaving behind a kind of
Urachus, which occasionally appears as a small urinary
Bladder. We have thus an explanation of the considerable
size of this organ ; of its purely membranous, or at least
very slightly muscular, structure; as well as of the peculiar
course of its Veins, which, as I have found by injection
in the Salamander, open into the Umbilical Vein, which
liere remains pervious through life, whilst in Man it forms
the round ligament of the Liver. In the Mud-Tortoise,
they communicate in the same manner with the two Veins
which correspond to the single Umbilical Vein of Man.

§. 671. The function of this part long remained as ob-
scure as its true character, inasmuch as it was considered
exclusively as a receptacle for urine, and even poisonous
properties ascribed to the fluid which Frogs and Toads
eject when pursued. That excellent observer, Townson,
was the first who diffused more correct views on the matter,
as we have already noticed. He found the fluid invariably
quite/ limpid, even in Toads perfectly tasteless; and re-
marked how extraordinarily copious must be the secretion
from the Kidnies, if these great receptacles were to be
viewed merely as urinary Bladders. Hence he farther
concluded, that they here form receptacles for the fluids so
abundantly absorbed by the skin, and only felt doubtful as
to the mode in which the absorbed matter was conveyed
to them; an office in which the Veins, the absorbing powers

250

of which have been rendered so very probable by many
modern experiments, may be supposed to perform an im-
portant part. The fluid is ejected only in order that the
animal may be less burthened in its flight : and hence
Townson observed, that it no longer happened when the
animal was sufficiently domesticated, and ceased to be
alarmed when touched. The observation made by him on
the Testudo orbicularis is particularly remarkable, from
which it would appear that these animals possess the power
of taking up water through the anus; inasmuch as he satis-
fied himself that when the Tortoise was placed in water
coloured with Litmus, the fluid subsequently ejected from
the bladder had the same qualities.

These phenomena are the more deserving of notice from
the very perfect manner in which they agree with what
has been said of the repetition of the respiratory function
in the urinary secretion : for, as in animals which breathe
water, we find air separated from it, and collected in a
bladder, so here, in animals that breathe air, water is depo-
sited in another bladder, which water may very possibly
contribute to respiration here in the same manner as the
air contained in the swim-bladder of Fishes; particularly as
the bladder is here to be considered as an allantois, which
we know to be truly branchial in the embryo of Lizards
and Birds, and as it is established that many Amphibia intro-
duce water into these cavities in the same manner that
inferior animals convey it into their branchial cavities.
More than this, the excellent experiments of Schreibers*
are enough to prove that the fluid contained in these cavities
is in no respect urinary, i. e. secreted from the kidnies ;
by which he has shown that the urine in these animals is
not secreted as a fluid, but in the form of a white friable
* Gilbert's Annalcn tier rhysik. b. .\iiii. s. 83.

251

concretion, which, according’ to the analysis of fecHOLZ,
consists of Uric Acid, 94 ; Muriate of Ammonia, 2; and
Phosphate of Lime, 3.33.

Lastly, true renal capsules have not yet been detected
with any certainty in this Ultiss: the organs desciibed as
such in Frogs by some anatomists we shall considei in coll-
ection with the sexual organs.f

Sfxtion III. Of the Urinary Organs in Birds.

§. 672. On opening the cavity of the trunk in a
Bird, and examining its posterior surface, we find in its
upper half on each side, a smooth, spungy, bright red mass,
sunk between the projecting bodies of the vertebrae and the
ribs, and which we have before learned to consider as
lungs: in the lower half, on the contrary, we find the

f Some more recent observations made by Dr. Davy are inconsistent
with the universality at least of the character here assigned to the bladder of
the Batrachia, as well as with the supposed qualities of its contents. He
states 'that in the Bull-Frog (It. taurina ) and Brown Toad (B.fuscus) the
ureters open into the rectum upon soft projecting papillae. The orifice of the
bladder upon the anterior surface of the rectum is large, and so situated as to
be well adapted for receiving the urine conveyed by the ureters, the escape
of which is prevented by the action of the sphincter of the anus. The fluid
contained in the bladder in both these animals, Dr. Davy found to be
strictly urinary, i. e. containing urea, but in variable proportion ; and some-
times, it would seem, so much diluted, that it is perhaps not unreasonable to
suppose that a part only of the contents were derived immediately from the
kidnies, and the remainder (by which the renal secretion is diluted) from the
skin, as suggested by Townson. f Phil. Trans. 1821, p. i. 95.) — Translator.

252

depressions between the bodies of the sacral vertebra and
the rib-like processes of the lateral bony parietes of the
pelvis occupied by other smooth and darker coloured masses,
which are the kidnies. (Tab. XV. fig. XII. w.) Hence,
consequently, even in their position, those organs offer a
repetition of the type of the lungs, and by that means indi-
cate the existence of a relation of their function to the
sexual actions, similar to that subsisting between motion and
the respiratory function. The bulk of the organs is still
in this Class proportionally very great, as proved even by
the consideration of their extent, but still more so by a
reference to their comparative weight; a point on which
experiments instituted by Tiedemann* prove that it is
very great in Wading and Aquatic Birds, (which are also
distinguished by the size of the liver,) amounting in the
Lapwing to in the White Diver to jq, of the weight
of the body ; and, on the contrary, in the Falcon, only to
The following may be viewed as the causes of this
very considerable size ; ls£, the predominance of the nega-
tive side of the reproductive powers in these animals
generally, as instanced in respiration, as well as the secre-
tions which form repetitions of it; 2d, the moderate size
of the lungs themselves, as compared to the extent of the
respiratory passages ; 3 d, the diminished perspiration from
the skin, which, even in Man, is attended by an increased
secretion from the kidnies; 4 th, the limited excretion of
water by the respiratory passages, for even in the greatest
cold Birds do not expire any aqueous vapour.

§. 673. The structure of the kidnies of Birds, as in the
preceding Classes, is still very simple; and the Ureters
here, also, arise by Separate radicles from the individual
lobes into which the kidnies are divided, partly by the dis-

* Tiedemann has particularly called attention to the two latter circum-
stances.

253

tribution of their vessels, and partly by the disposition of
the bones on which they rest, and by which we find them
divided more particularly into a smaller upper and larger
lower portion. They are surrounded by cellular structure,
and, like the lungs, are covered on their anterior surface by
the peritoneum. The ureters descend at the posterior part
of the pelvis, are evidently muscular, and enter the cloaca
at the edge of the rectum. The urine of Birds is very
similar to that of Lizards, (§. 671.) and in the same manner
contains so much Uric Acid, Carbonate and Phosphate of
Lime, that immediately after its secretion it assumes a solid
form, and usually covers the excretion from the intestinal
canal in the form of a white coating, which, when exposed
to the air, speedily hardens into a friable powder. Accord-
ing to Cuvier, the Ostrich and Cassowary alone have the
power of evacuating the two excretions separately ; but in
other species, particularly the Gallinm, when there is an
egg in the oviduct, I have frequently found the termination
of the rectum much distended with fceces, though none had
entered the cloaca, which contained only some urinary
concretions.

§. 674. There is ordinarily no trace of a urinary
bladder in Birds, the allantois, which in the Chick is con-
nected with the cloaca by means of the urachus, being here
in general perfectly obliterated. Iu addition to the kidnies,
we first meet the Renal Capsule in a sufficiently distinct
form in Birds, though, in proportion to the kidnies, much
smaller than in Man for instance ; (in the same manner
that the spleen was small in proportion, or even wanting,
in the large-livered Mollusca, and also the renal capsules
in relation to the large kidnies of Fishes and Amphibia.)
These organs are placed between the superior lobes of the
two kidnies, close to the testes or ovaria; are for the most
part somewhat lobed, oval, and of a yellowish-red colour.

254.

Meckel* observed two substances in them in the Casso-
wary. According to Tiedemann, they are largest at
breeding tinie;j- whilst, according to Tannenberg, a blind
process of the seminal duct is lost in their substance.

Section IV. Of the Urinary Organs in Mammalia.

§. 675. Here again we may consider the human type

as the general standard for the other species of this Class;

and, consequently, ordinarily find a more complicated

internal composition, which we are therefore enabled to

subdivide into several parts ; Papillae, which secrete the

urine ; Infundibula, which pour it into a common pelvis ;

whence it is conducted bv the Ureters into the bladder,

•>

and thence evacuated by the sexual passages. There is by
no means, however, any deficiency of approximations to
the preceding formations. The kidnies themselves are dis-
tinguished in the Cetacea by their peculiar structure,
which most distinctly presents the composition of the organ

, * In his Abhandlungen aus dcr mensclu und Vergl. Anatomie.

f This is not the place for discussing the function and character of these
organs : I cannot help remarking, however, that much of the obscurity con-
nected with them disappears, if we allow that a peculiar secretion, or any
similar definite function, is not indispensably requisite ; and that it is per-
fectly conceivable that the mere existence of certain organs may have impor-
tant effects in any given system of organs. Strictly speaking, every part
of the body is a secreting organ, inasmuch as it selects and appropriates to
itself certain portions of the general mass of fluids. Why, then, may we not
suppose that it is the office of the renal capsules to separate superfluous ma-
terials from the Urinary and Sexual Systems merely by employing them in
their own nutrition ?

255

by little distinct lobes, as in the preceding Classes, and
appear rather as common conglomerate glands than as
proper compact secretory organs. They consist of upwards
of two hundred distinct conical-shaped masses, with the
broadest end turned outwards, so that Hunter* compares
the external surface of the whole kidney to a pavement,
each presenting a tubular structure internally, and termi-
nating in a papilla surrounded by a membranous infundi-
bulum, the united points of which open into the ureter at
the narrow extremity of the kidney. The structure of the
kidnies is likewise commonly precisely similar in the Amphi-
bious Mammalia, (see the kidney of the Seal, Tab. XIX.
fig. XXII.) and also in the Otter and Bear, although the
number of distinct lobes gradually diminishes in them,
whilst the infundibula no longer terminate directly in the
ureter, but are previously united in a pelvis. The division
of the kidney into separate lobes of this kind is much less
perfect in most other Mammalia, being chiefly confined to
the first periods of existence, in Man for instance ; the
number of these divisions, which is indicated internally by
the number of papillae, being at last so much reduced that
in animals with claws we find but a single papilla remain-
ing ; whence, also, the kidney appears smooth externally,
and of a more globular form. As to the position of the
kidnies, it is to be remarked that in large as well as small
quadrupeds the right is invariably placed somewhat higher
than the left.f

* Philos. Transact. 1787,rp. 413.

f In the Cat Genus the depressions left on the surface of the kidney by
its imperfect division into lobes are occupied by from seven to nine principal
venous trunks, which increase in size as they converge towards the sinus of
the organ in order to empty themselves into the renal vein. They resemble
the sinuses of the brain ; their canal, when laid open, presenting at the part
next the kidney an angle perforated by the orifices of veins coming from the
organ. (Cuvier, Comp. Anat. v. 229.) — Translator.

255

§. 676. The remaining’ part of the course of the ureter
is the same in Mammalia as in Man, terminating in a urinary
bladder in all the species of this Class except the Orni-
thorhynchi, which offer a repetition of the structure of the
Amphibia, in so far as the Ureters open directly into the
common urinary and genital canal, which leads to the
Cloaca, and, consequently, are only indirectly connected
with the Bladder ; an organization which appears to prove
that in these animals, as in Amphibia and Birds, the Allan-
tois (the remains of the Urachus of which form the Bladder
in Mammalia) arises from the expansion of the Rectum,
the Cloaca: whilst, on the contrary, in other quadrupeds it
is connected solely with the genital passages. The shape
of the Bladder in Mammalia presents no very essential
varieties; but its elongated form in several Ptodentia, and
in young animals, ( e . g. the Calf,) is worthy of notice, as
a proof of the origin of this organ from a portion of the
Urachus. It is in general found small, particularly in pro-
portion to the sexual organs (Vesiculse Seminales, Testes,
Ovaria), of which we have instances in the Hedgehog, as
well as several Rodentia. (Tab. XX. fig. VI. d.) The
assertion, that the Bladder is always larger in herbivorous
than in Carnivorous Mammalia has been already contra-
dicted by Cuvier, who observes, that its comparative size
is regulated not so much by the kind of food of the animal
as by the greater or less degree of muscularity of the organ,
the muscular structure in this as in the other parts of the
body generally predominating in the Carnivora.

§. 677. The Renal Capsules of Mammalia so far agree
with the Kidnies, that, according to Cuvier, they are, in
the amphibious Mammalia, divided in the same manner
into several little lobes; whilst in the terrestrial species
their shape, either bean-like or more triangular, resembles
that which the kidnies here most usually present. It is

257

remarkable, too, that in size there is somewhat of the same
proportion as that existing- between the Spleen and Liver,
viz. that^the Capsules are found smaller in proportion as
the Kidnies are more perfectly developed : thus, in the
Rodentia, they are very large ; according to Cuvier, as 1
to 8 — 5, in the Guinea-Pig ; whilst, on the contrary, they
are singularly small in the amphibious Mammalia, as 1 to
150 in the Seal, according to Cuvier. He found cavities
in them in the Elephant only, though I have sometimes
met such a structure in young Pigs and Dogs. The changes
which take place in the Renal Capsules in Man occur also
in other Mammalia, they being very large in the foetus,
smaller in the adult, and smallest in old age.

C. Of Secretions in or near the Respiratory Organs

themselves.

§. 678. As in other secretory organs, we remarked that
the most important and most essential secretions were fre-
quently accompanied by others less so ; of which we have
an instance in the secretion of mucus in the urinary blad-
der, so also do we observe something similar in the respi-
ratory passages ; of which kind are the perspiration, as it
is called, of aqueous fluid from the skin and lungs, as well
the secretion of mucus in the true respiratory passages
both of Gills and Lungs. The parts, however, which pro-
duce such accessory secretions are so completely integral
portions of the greater organs that a precise consideration
of them forms an object of Physiology rather than Ana-
VOL. II. s

258

ftpmy, and consequently is unsuited to tlie present occasion,
though it might be in several respects productive of interest-
ing results, were we only, for instance, to compare the
•expired air loaded with water in Mammalia with that of
Birds (§. 672.) which scarcely contains any. Consequently
we can here speak only of some glandular organs ; which,
though not the seat of peculiar secretions any more than
the Renal Capsules, yet by their mere growth or decrease
(see Remark on §. 674.) may, and even must, have a very
important relation to the respiratory function, inasmuch as
in different animals, and even in different periods of life,
they undergo important changes corresponding to those in
the state of the respiratory function. It will be easily
seen that the Thymus and Thyroid are here alluded to.

1). Of the Thymus and Thyroid in the Superior
Classes of Animals.

3, . ; !'

§.679., When we reflect, that the developement of
these two organs in Man is chiefly confined to the earlier
•periods of life, nay, that the Thymus appears to vanish with
the increase of age, it must at first view seem contradictory
that, they should be altogether wanting in the lower
Classes of Animals; that they should be found in some only
of the Amphibia and Birds; and that they are distinguish-
able with perfect precision in Mammalia alone. This
contradiction, however, in part disappears, if we consider
that in the inferior Classes the limited extent of Respira-
tion dependent on the less perfect organization of the

259

respiratory cavities, or rather on their incomplete distinction
from the other parts of the body, may be more easily com-
pensated by the farther advanced developement and acti-
vity of other organs, particularly the Liver* and Kidnies ;
an idea which will enable us to explain the formation of
peculiar organs for the purpose of supplying the imperfec-
tion of respiration during the early periods of the existence
of Mammalia. Nay, even the imperfection of the respi-
ration of the foetus of Mammalia, compared for instance
with the embryo of Birds, may render the existence of
such organs necessary. In Fishes, consequently, there are
no traces either of Thymus or Thyroid ; and though it has
been lately attempted to draw a comparison (of much interest,
it is true) between the Swim-bladder and Thymus, it by nQ
means coincides with it, that a close consideration of the
function of the former appears to prove that it performs
a part only of the respiratory function ; that its activity is
undiminished when the animal attains its full develope-
ment; and that there is not any evidence of any such
antagonistic relation between it and the Gills as that found
between the Lungs and Thymus.

§. 680. As to the Class Amphibia, I find in Frogs
(Rana esculenta) two reddish glands (Tab. XIII. fig. VI.
d.) on each side of the Os Hyoides, and on the inner side
of the laryngeal pouch, which appear to form a Thyroid,
ond \yhich, by their truly glandular texture and colour, are
sufficiently distinguished from the little fatty bodies that
form towaids winter, and disappear in spring, and which
have been described by Treviranus| as a Thyroid or

It is in this respect important to observe, how in the Amphibia, and
partly also in Birds, the liver extending considerably upwards in front of the
Lungs, and inclosing the Heart after the manner of a Thymus, appears to
correspond to the position of that organ.

* Vermischte Schri/lcn Anatom, und Physiol Inhalls, b. i. s. 96. On the

s 2

260

Thymus. Those little bodies can only be so far compared
to a Thyroid or Thymus as they are the seat of an
excretion of phlogistic matter, which their formation may
perhaps tend to consume ; but in other respects they pre-
sent more analogy to the collections of fat common in
hybernating animals. I find the Thymus very much deve-
loped in the Mud-Tortoise (T. lutaria), forming a reddish
cordiform body, about half an inch broad, and occupying
the space between the two Axillary Arteries arising from the
ascending Aorta. In Serpents, an oblong glandular body,
lying above the heart, appears to deserve the name of
Thyroid or Thymus ; and I should probably be justified in
considering of the same nature two half fatty, half glan-
dular bodies, which I remarked at each side of the neck in
a young Crocodile. (Tab. XII. fig. XIX. e.)

§. 681. In Birds, also, an ambiguous organ of this kind
has been discovered, viz. two reddish, oval, minutely gra-
nular Glands placed at each side of the Trachea, dose to
the inferior larynx, consequently at the entrance of the
cavity of the Thorax, and to which no excretory duct has
yet been detected. Meckel, f who views it as the Thymus,
states that it is chiefly found in young Birds, and in the
adults of some diving Birds only. Tiedemann,! however,

same occasion M. Treviranus asserts that the "Ganglia I have described on
the Sympathetic of Frogs are merely collections of fat about the Nerve ; but
a more accurate examination of my delineation of them might have satisfied
him that I spoke not of those Ganglia on the front part of the neck, but of the
superior large ones placed on the Interverteb.al Nerves of the Brain and
Spinal Marrow ; (see p. 180 of my Essay on the Nervous System. ) of which
Weber, also, (Anat. Comparata Nervi Sympathici, p. 41,) has demonstrated
that they belong chiefly to the Sympathetic Nerve.

■}• In his Abhandl. a. d. Mensch. u. Veryl. Anat. u. Phys. Halle, 1S06;
and the 4th volume of his Transl. of Cuvier’s Comp. Anat.

{ Zoologie, b. ii. s. 688. I can so far confirm his suspicion as to the
existence of this organ in the Coot, that I have myself there found a glandu-

261

asserts, on the contrary, that he has found the same organ
in other species, (Falcons, Herons, Bustards, Doves, Mag-
pies, Starlings:) whence, and also from its situation in the
vicinity of the vocal organs (the inferior larynx), he agrees
with Ballanti in considering it as the Thyroid. It is by
no means impossible that here, as well as in Serpents or
Crocodiles, a single mass may unite in itself the character
of both organs.

§. 682. As already mentioned, it is in Mammalia that
we are most precisely able to discover the existence of these
two organs. First, of the Thymus : it appears to be almost
exclusively peculiar to the foetus in this Class ; and in adults,
to exist in the natural state, according to the excellent
researches of Meckel,* in those instances only in which
respiration is occasionally interrupted for a shorter or longer
period ; consequently in those species which dive, burrow,
or hybernate; of this kind are the hybernating and burrow-
ing Rodentia, the W easel, Mole, Hedgehog, Bears, Otters,
and probably all the amphibious Mammalia, being distin-
guished by the permanent, or at least long continued,
existence of a Thymus, occasionally of very considerable
size, sometimes ascending high in the neck, or divided
into several lobes. As to the Thyroid, it appears to be
common to the whole Class, inasmuch as Cuvier has found
it eyen in the Cetacea, where its existence was denied by
Hunter. It is remarkable, however, that in the Porpoise
as well as the Seal it resembles the lateral glands near
the inferior larynx of Birds, in being formed of two per-
fectly distinct halves, — a separation which exists also in
many other Mammalia, e. g. the Elephant, Solipeda, Dogs,
Cats, Bats, and several Rodentia, at least in the adult

lar orgau in the same situation, though smaller, of a more globular form, and
a more yellow colour.

* Loc. citat,

262

animal; for in tlie foetus, or young animal, the organ is
either larger, or forms but a single mass. The two halves,
however, are connected, even in the adult, by one or
more transverse portions, in Apes, Bears, several Rodentia,
and Man himself ; on which point we may remark, that
in the latter this organ is proportionally of greater
extent than in other Mammalia, which serves as a
forcible argument for the opinion of those who think it
probable that its function is intimately connected with the
formation of the voice.

§. 683. A retrospect of the history of all the secre-
tory organs just considered will readily convince us that
in Man we can here no longer discover the same pecu-
liarly perfect developement as in most of the organs
before examined. But though in this respect he does
not possess the same pre-eminence, yet it merits a par-
ticular consideration, that it is precisely in those organs,
which, as purely vegetative, are completely opposed to
the influence of the Nervous System, that Man is scarcely
essentially distinguished from other Animals.

263'

-i

Chapter III. Of the Vascular System.

§. 684. In what has preceded we have traced through
the series of Animals the developement of those organs, by
means of which either extraneous materials are taken into
the body in order to be assimilated to it, or internal organic
materials are either absolutely excreted, or secreted in sub-
servience to particular purposes. In the same manner that
the Organs of Sense and of Motion required to be united
by the Nervous System, so here the existence of these
two functions usually renders necessary1 an intermediate
member, — the Vascular System. Consequently, its divi-
sions or subordinate systems must present themselves in
more various forms in proportion to the multiplication of
their points of contact with other organs ; in other words,
in proportion to the increase in the complication and per-
fection of the animal organization at large; Whilst, for
instance, we find in Man a peculiar system (Lymphatic)
for the absorption of extraneous and of internal organic
materials, as well as a system (Sanguineous) for the uni-
form distribution of fluids to all parts of the body, which is
again subdivided into the Arterial and Venous Systems,
and also into a greater system circulating fluids through
the body in general, and a lesser system for the circulation
of the same fluids through the respiratory organs ; in the
inferior Classes, on the contrary, these systems are much
less variously developed, and more particularly the Animals
without Brain or Spinal Marrow differ from the superior

264

Classes scarcely less in their Vascular System and fluids than
in their Nervous System.

A. Vascular System in Animals without Spinal Marrow

and Brain.

§. 685. The most important peculiarities characterizing
fthe Vascular System of the three inferior Classes of Animals
consist, ls£, as regards its formation, the absorbing vessels
not being apparently distinct from those which distribute
the fluids ; nay, the Respiratory not being distinct from the
General Circulation, or the System (Arterial) which distri-
butes the fluids not distinct from the System (Venous) by
which they are brought back again : 2 d, as regards the
mass of fluids, which, being ordinarily merely lymphatic,
and flowing in vessels, or even stagnating in cavities of the
body, keeps up the constant interchange of organic ele-
ments. We might therefore correctly institute a comparison
between the system which in the superior Animals may be
called the lowest, viz. the Lymphatic, (so similar in many
respects to the system of sap-vessels in Plants,) and that
which forms the sole system of the inferior gradations of the
Animal Kingdom ; nearly in the same manner that a similar
comparison was instituted with the Ganglionic System as
regards the Nerves. For, as the Ganglionic System has
more importance in these than in the higher Classes of
Animals, so also is this form of the Lymphatic System more
developed in the one than in the other case. It is not
merely that the single kind of vessels found in the lowest
organizations constitutes at once the agent in absorption

265

and excretion, (whilst in the Lymphatics of the superior
Animals there is ordinarily only a retrograde motion of
fluids to the central points,) but also the increase in the
perfection of the internal structure of such organizations is
accompanied by a division of those vessels into subordinate
systems for distributing and for returning the fluids, as
well as for exposing them to _ the influence of Respiration,
and by the formation of central organs (hearts) ; the whole
thus approximating more and more closely to the blood-
vessel system of the superior Animals, and ultimately
differing from it in this respect alone, — that it includes
absorption, and ordinarily conveys colourless lymphatic
fluids only. Hence, also, we have here again the same
state of circumstances as in the Nervous System; where we
found that the chain of Ganglia of the inferior Animals
presented the relations both of Brain and Spinal Marrow,
differing in this respect only, — that it was placed on the
abdominal surface, and that there was not any Sympathetic
Nerve.

Section I. Vascular System in Zoophytes.

/ "

§. 686. Comparative Anatomy has hitherto been as little
able to trace the existence of a Vascular as of a Nervous
System in the lowest species belonging to this Class.
In Infusaria, Polypes, as well as in the inhabitants of
Corals and Sponges, the uniform gelatinous (primitive
animal) mass alone suffices to keep up the constant change
of composition, by its universal impregnation with fluids,
produced by mere elective attraction and repulsion depen-

2G6

dent on organic laws. "1 In the Medusae and Echinodermata,
on the contrary, we discover definite canals for the passage
of fluids in the interior parts of the body; the vessels of the
Medusae deserving a particular notice, inasmuch as we shall
find their formation subsequently repeated in the Ovum of
the superior Animals. From the gastric sac, as from a
Keceptaculum Chyli or Heart, radiated and considerably
ramified vessels (Tab. I. fig. IX. A. c. d.) proceed towards
the margin of the body, there to empty themselves into a
circular vessel (d.) ; of which we may observe, that it might
be considered as an extremely simple rudiment of the great
circulation of superior Animals, in case we view the radiating
as chyliferous vessels. In the Echinodermata, also, there are
several traces of peculiar vessels for the diffusion of fluids.
Cuvier has described vessels, in the Holotluiriae for in-
stance, which are even distinguishable into those that dis-
tribute and those that return the fluids.f $

* The part formerly described as a heart in the Wheel-animal is, in fact;
the stomach ; but if a more complicated structure actually exists in this little
animal, (for it is said to have eyes,) we may ask whether it should not be
considered as a microscopic species of Mollusca ?

f Comp. Anat. vol. i. p. 255. In a more recent work {LeRigne Animal
t. iv. p. 6,) he says of the vessels of the Echinodermata generally, “ Une
“ sorte de systeme vasculaire, qui a la verite ne s’etend pas a tout le corps,
“ entretient une communication avec diverses parties de l’intestine et avec
“ les organes de la respiration.”

| In the Holothuria tubulosa, where there are three folds of intestine, the
middle fold lias along one of its sides a vessel, which becomes narrow at each
extremity, receiving a great number of short branches from a vessel to be
subsequently described, and giving off others from the opposite side, which
subdivide considerably, and then unite into a certain number of vessels, which
by their junction form another trunk. The net- work produced by this sub-
division of the branches of the first vessel before they unite to form the
second, is intimately intermixed with the ramifications of an arborescent intes-
tine, opening into the cloaca, and appearing to form a respiratory organ. The
first vessel, therefore, is a Pulmonary Artery, receiving the blood from the

Section II. Vascular System in Mollusca.

A. Acephala.

§. 687. The very distinct developement of the respira-
tory organs in this whole Class, and even in the first Order,
is accompanied by a corresponding extent of developement
of the circulation, which is ordinarily already carried on
according to the same laws as in the superior Animals, and
even in Man himself. Among the Acephala the Vascular
System appears to be least perfectly evolved in those
instances in which there is a branchial cavity in part be-

body in order to transmit it to the respiratory organ. The second great trunk
is divided into four large branches united by a transverse branch.
Two of these branches receive the blood from the respiratory organ,
and run parallel to the first trunk, the intermediate space being occupied
by the ramification of the vessels connecting them. These two are a kind
of Pulmonary Veins, conveying the aerated blood into the other two branches
by means of the transverse canal, and by their extremities, where there is a
visible communication. The other two branches, consequently, are aortic,
proceeding along the first fold of intestine, and furnishing it with blood by
means^df numerous little arteries, which penetrate its substance directly.
The superior branch having reached a certain height, bifurcates, in order to
form a circle around the (Esophagus, which gives off five branches following
the direction of the fleshy mass of the mouth, and distributed longitudi-
nally upon the general covering of the body. The blood is returned from
this covering by veins situated within the mesentery, and also by a trunk,
which appears to form a kind of Vena Cava. The latter is formed by four
principal branches connected by a transverse canal : two of those branches,
situated along the first fold of intestine, receive its blood, whilst the other
two transmit it to the pulmonary vessel by means of the little branches
mentioned at the commencement/ of this description. (Cuvier, Comp.
Anal. iv. H5.) — Translator.

2G 8

longing to the intestinal canal, e. g. in the Ascidite; at least
in a large species, very similar to the A. microcosmus , I
observed merely a membranous cavity at the fundus of the
muscular sac, (Tab. II. fig. I. o.) which appeared calculated
for receiving the fluids of the body by means of some
branches from the liver, and to distribute them to other
parts by means of a canal running on the dorsal surface,
(q.) In the remaining Acephala, possessing branchial
laminse, the veins of the body convey the blood into the
branchial vessels, whence it is again returned to the heart-
by means of branchial veins, and thence distributed through
the body by one or more arterial trunks. The form and
position of the heart, however, vary materially in the dif-
ferent species.

§. 688. In the Teredo the Heart, according to Home,*
is situated on the dorsal side,f and presents two Ventricles,
(Tab. II. fig. XV. f. f.) which receive the branchial blood by
means of two auricles, (e. e.) and evacuate themselves into
a dilatation at the commencement of the Aorta, (g.) The
Brachiopoda, e. g. Lingula, and also the Genera Area and
Pinna, have, according to Cuvier, a separate aortal heart
for the branchial blood of each half of the body. In the
Oyster the heart is placed between the liver and the muscle
that closes the shell, and extends from the back forwards
towards the gills. In the Acephala, which have two similar
(symmetrical) shells, e. g. the River Muscle, the heart is
situated on the dorsal side below the hinge (cardo), within
a thin sac, through which it may be clearly seen pulsating
in the living animal when taken out of the shell. (Tab. II.

* Philosoph. Transact. 1806, p. 184.

f This position of the Heart on the dorsal surface is altogether peculiar to
Animals without Brain and Spinal Marrow ; and, together with the situa-
tion of the principal nervous cord on the abdominal surface, indicates the
preponderance of the vegetetive structures.

269

fig. XI. c.) It is there of an orange-yellow colour, oblong,
(fig. XIII. c.) terminating anteriorly and posteriorly in
arterial trunks, and possessing powerful muscular fibres.
The two auricles, which receive the blood from the gills,
are placed on each side of the heart, and composed of very-
thin membrane. (Fig. XIII. d. d.) I have already (§.
437.) mentioned the remarkable fact in the organization of
these Bivalves, that the Rectum passes through the centre
of the Heart. It is worthy of notice, also, that the Tere-
dines, according to Home, possess red blood, whilst the
fluids contained in the vessels of other Mollusca are clear
and serous.

B. GAStEftOEODA.

§. 689. Here, also, there is a double circulation through
the body and through the lungs, though the Heart is inva-
riably single : its form and position, however, are different,
the latter being regulated by the situation of the respira-
tory organ. We may describe as instances the disposition
of the Vascular System in some Species. In the Helix
pomatia , where the Heart and its principal vessels have been
pretty accurately described and depicted by Swammerdam,
and- which is one among the many Gasteropoda of which
the Anatomy has subsequently been so well investigated by
Cuvier, in the Annales du Museum , the Heart is placed
within a delicate Pericardium to the left side, and behind
the pulmonary cavity, between the latter and the Liver.*
(Tab. III. fig. II. m.) The thin blueish milky blood
arrives by means of a capacious pulmonary Vein and a

• A position, consequently, which is precisely the same as that found in
the superior Animals.

270

roundish Auricle (fig. III. i. k.) at the muscular Ventricle
(I.), which is rather triangular and provided with Valves:
and is thence distributed to the rest of the body by means
of an Aorta somewhat dilated at its origin. The blood is
brought back by two Vense Cavae, a larger one following
the concavity (fig. III. f. fig. I. k.), and a smaller one
(fig. III. g.) running along the convexity of the convolu-
tions of the body : the two are connected by a canal of
communication (h.), from which the Pulmonary Arteries
arise, ramifying minutely on the inner surface of the lungs,
and ultimately terminating in the Pulmonary Veins.

§. 690. When the Respiration is performed by Gills,
the Heart is usually situated immediatly behind them, as,
for instance, in the Aplysise; where, according to Cuvier,
the Vascular System in general presents many peculiarities.
There are here at the sides of the body two strong and
muscular venous (Cavse) trunks, that open into the cavity
of the abdomen by peculiar orifices, which are, probably,
absorbing apertures, supplying the deficiency of a distinct
Absorbent System. The two trunks unite to form the
Branchial Artery, from the extremities of which the Blood
is conveyed, by a Branchial Vein, first into the Auricle
(Tab. III. fig. VII. x.), then into the Ventricle (y.), and
is thence again distributed by a principal trunk dividing
into the Hepatic Artery (6.*), the Gastric Artery (6.), and
the Aorta (z.) At the root of the latter is placed a pecu-
liar double Pecten, which is filled by injection from the
artery, and again returns its blood to it. In the Viviparous
Snail, the Heart is situated in the same manner between
the Gills and Liver. (Fig. X. k.)

271

C. Cephalopoda.

§. 691. The Organs of Circulation in the Sepiae differ
from those of all other Mollusca, in presenting a greater '
number of central cells or Hearts than any other animal,
viz. three: of these, one (the Aortal Heart) corresponds
to the single or double heart of other Mollusca, whilst the
other two (Pulmonary) serve to propel the general mass
of blood into the branchial vessels. In the Cuttle-fish, for
instance, (and with slight variations in the other species,)
the principal trunk of the Veins of the body descends from
the head and divides into two branches distributed to the
Gills, presenting in this situation an organization which
appears to correspond to that of the Venae Cavae in the
Aplysiae; the Veins being provided with numerous glan-
dular appendages which communicate with those vessels,
and probably absorb fluids from the cavity of the abdomen.
(Tab. IV. fig. XVII. d. d.) The venous trunk on each
side terminates by means of an orifice furnished with valves
in a Branchial Heart, (b. b.) which propels the merely
serous blood through a Branchial Artery into the Gills,
whence it passes by the Branchial Vein (e. f.) on each
side, (which presents a slight dilatation,) into the Aortal
Heart, through an opening furnished with Valves. The
Aortal Heart itself is powerfully muscular, is placed trans-
versely in the body (a.), and sends upwards a principal
arterial trunk (g.), which has a dilatation at its root, is dis-
tributed to the different parts of the body (fig. II. s. t.),
and in the Head, forms a Circle, like the Nervous System,
around the CEsophagus.

272

Section IIL Vascular System in the Articulata.

A. Vermes.

§. 692. As regards the Vascular System, the Intestinal
Worms are circumstanced in the same manner as Zoo-
phytes, viz. there are either no traces of any such, as, for
instance, in the Hydatids, or, there are some canals in the
interior of the body, as in the Toeniae, which, however*
appear to be rather ramifications of the Intestinal Canal
than vessels; nay, the extraordinary absorption by the
external surface in all these animals, already noticed
(§. 44S. 444.), appears to be the consequence rather of
immediate impregnation by fluids than of the action of
peculiar absorbent vessels. It is otherwise in the extrane-
ous Worms, where there is not only a distinct, though in
many respects still very imperfectly understood, Vascular
System, but also a red-coloured fluid or Blood. In the
Leech, for instance, there are two larger, serpentine, and
distinctly pulsating lateral vessels, (Tab. V. fig. VIII. h.
X. a.) and a smaller, central dorsal Vessel; of which the
former, according to Cuvier, appear to be a venous, and
the latter of an arterial nature. There is no trace, how-
ever, of distinct central organs; nay, according to Thomas, f
the blood does not appear to move in any regular manner,
but sometimes backwards, and sometimes forwards, which,
however, I am the less inclined to believe, as I have suffi-
ciently ascertained from the observation of living Earth-
| Memoire pour servir a VHistoire des Sangsttes.

273

worms, how easy it is to make a mistake, and how fre-
quently the motion of the rings of the body may lead us
to imagine that the blood moves sometimes backwards
and sometimes forwards in the same vessel, though such is
by no means really the case. How minute and numerous
the ramifications of the vessels are in the Leech, is proved
by the multiplicity of the branches surrounding the nervous
Ganglia. (Tab. V. fig. XII.)

§. 693. The Vessels already alluded to in the Earth-
worm are more distinct than those of the Leech. In it I
find three principal Vessels stretching through the body, a
superior one, probably arterial, (Tab. V. fig. IV. a.) and
two inferior, of which the largest may be considered as a
Vena Cava, whilst the other smaller one, placed below it,
and of a more brilliant red colour, appears to be the Bran-
chial Vein, which, probably, receives the blood conveyed
to the respiratory vesicles by branches of the Aorta, and
intermixes it with the rest of the venous blood at the ante-
rior extremity of the body, where the superior and inferior
trunks communicate. The connection between the supe-
rior and inferior longitudinal vessels is particularly remark-
able, from the circumstance that it is effected by means of
circles of vessels around the CEsophagus, (again reminding
us of the Nervous Circle around the same part,) the circles

I each presenting several heart-shaped dilatations, (Tab. V.
fig. II/ m. m. m. fig. V.) which, however, rather give them
the appearance of Lymphatics contracted at the valves and
dilated in the interstices, than actually represent the form
of the Heart of superior animals. According to Cuvier,
there is a similar, though somewhat more complicated,
V ascular System in the Lumbricus marinus : according to
Oken,* however, the blood of the Branchial Veins on each
side, placed close to the Vena Cava on the abdominal sur-r

* Isis, b. i. h. 4. s. 470.

VOL. II.

274

face, is poured at tiie anterior part of tlie body into two
Auricles, and thence into two Ventricles, which send off
Arteries both upwards and downwards, and then unite to
form a central longitudinal vessel closed superiorly and
jnferiorly.*

B. Crustacea.

§. 694. It is particularly in the Branchiopodous Crus^
tacea, e. g. the Squillae, that the central organ of Circula-
tion approaches most closely to the elongated Heart lying

* In the Lumbricus marinus, a large vessel is stretched along the back
between the branchiae on each side, diminishing in size at both extremities.
It transmits its contents by its anterior end, and receives 15 lateral vessels
on each side, viz. one from each of the branchiae. These vessels correspond
to pulmonary veins, and convey the blood from the branchiae into the great
vessel, which becomes distended by the contraction of those organs. A cor-
responding number of vessels convey the blood to the branchiae, though all
of them do not arise from the same trunk. The nine first are given off from
a large trunk situated upon the intestinal canal, immediately below that
already described. The others arise from the posterior part of a vessel
parallel to the two former, but situated below the intestinal canal. The two
great longitudinal trunks, therefore, send the whole of the blood contained in
them to the branchiae alone, performing the office at once of Venae Cava
and Pulmonary Arteries, for such of their branches as do not proceed to the
branchiae are veins which receive the blood from all parts of the body.
These branches of the Vena Cava expand in a very regular manner on the
yellow surface of the intestinal canal, with which their purple colour form9
a beautiful contrast. They arise primarily from two vessels arranged at the
sides of the intestinal canal, performing the office of Aorta, and communi-
cating at the lower part of the (Esophagus with the great Pulmonary Vein
first described : at the point of communication is a swelling which presents
more distinct motions of dilatation and contraction than the rest of the sys-
tem, and which may in some respects be considered as a Heart, though its
parietes are not thicker than those of the other vessels. (Cuvieu, Comp.
Anal. iy. 411.) — Translator.

275

on the back of the Mollusca, or to the Aorta stretched
along the back of Vermes, the Heart itself being here little
else than an Aorta extended along the back, receiving its
blood from the Branchial Veins and propelling it into the
other parts of the body. It is thence collected into a V ena
.Cava placed on the abdominal surface, and fiom it passes
again into the Gills, the mode of Circulation, consequently,
being here the same as in the Mollusca. In the true Crabs,
the Heart is more rounded ; in the Cray-fish, it is fringed
at the margins, is placed immediately below the dorsal
shield, (Tab. VI. fig. IX. fig. IV. a.) being distinctly seen
to pulsate when it is removed, and sends off several Arte-
ries both forwards and backwards. (Fig. IV. b. c.) The
substance of the Heart is distinctly muscular, though still
very soft : the Arteries are delicate and perfectly trans-
parent tubes.

C. Insecta,

695. It is in those Species only where the respiratory
apparatus differs but little from that of the Orders hitherto
considered, that we find a distinct Vascular System capable
of keeping up a Circulation, e. g. in the Araclmida, which
approach in so many particulars to the Crustacea. In
Spiders, as well as Scorpions, the investigations of Cuvier,
Meckel, and Treviranus, have shewn that the Aorta-
like Heart extended along the back, (and of which the
pulsations may be seen by the naked eye in those Spiders
which are not covered with hair,) gives off several vessels,
of which some are constantly connected with the Branchiae*
and others with the (so called) adipose Bodies, (Tab. VII.
fig. VII. a b.) though the actual mode of Circulation can-
not be discovered with any certainty on account of the

t 2

276

extreme delicacy of the vessels. If we may trust to ana-
logy, however, it must agree pretty closely with that of the
Crustacea.

§. 696. As to other Insects, though some of the older
anatomists have supposed that they have observed vessels
and a Circulation in particular instances, all the more recent
observations agree in denying their existence, and in the
supposition that the fluids of the body permeate the internal
organs without being contained in vessels, which perfectly
accords with the manner in which the Tracheae convey air
to every point of the body, as well as with the peculiar
forms of the secretory organs. (§. 648.) One vessel, how-
ever, still remains, and by its evident pulsation, as well as
by the absence of all communicating canals, has given rise
to the most various suppositions. It is placed along the
bach, in the same situation where a true Aorta-shaped
Heart presents itself in the preceding Orders, and even in
the Arachnida; and, consequently, has received the name
of the Dorsal Vessel. In all the Insects which have been
examined with regard to this point, it presents itself as a
thin membranous canal of uniform size, except that it is
somewhat contracted at its extremities, and that by its pul-
sations, (greatest, according to Lyonnet, at the lower
extremity,) it sometimes appears as though it had alternate
points of contraction, and was on that account described
by Malpighi- as a series of Hearts. The very minute
ramifications of the Tracheae which surround this canal on
each side deserve notice, (Tab. VII. fig. XIII.) as well as
its attachment to the back by peculiar bundles of muscular
fibres. The Dorsal Vessel is found in all stages of the
developement of Insects, though, according to the excellent
investigations of Marcel de Serres,* its diameter is less

* Maqasin Encjjclopcdique de INTilt.in. Mai. Juin. Sept. 1814. “06-

“ str nation* sur les Usages du Vi/isseau Dorsal.”

277

uniform in the perfect Insect than in the Larva. He
states, also, that the Muscles and Tracheae appear to
have more influence over its motion than the Nerves; and
moreover, that the organ is so little essential to life, that
Caterpillars, for instance, when it is removed, or when its
contained fluid is coagulated by Muriatic Acid, continue,
nevertheless, to live and breathe : whilst, on the contrary,
Spiders and Scorpions die when the Heart is removed. It
still remains to be determined whether this organ have any,
and what, definite function ; or whether it should not rather
be considered as a remain of an earlier type of formations,
gradually losing its functions in these organisms ; an idea
which is rendered not improbable by the observations above
alluded to. I am but little inclined, however, to agree with
the suggestion of M. de Serres that it is the secretory
organ of the Adipose Body, inasmuch as it is contradictory
to suppose that a canal should absorb fluids by its parietes,
and then exude them in the same manner, but in a different
form ; besides, that as the character of those bodies is that
of chylous masses, it is more probable that they are secreted
by exudation through the parietes of the Intestine.

Remark. In my Essay on the Nervous System , p. 75, I
have alluded to the remarkable circumstance, that the
embryo of the superior Animals presents, in the same
situation as the Dorsal Vessels of Insects, a similar
1 canal, impervious at the extremities, and containing
a fluid in which nervous fibres are subsequently
deposited, converting it into the Brain and Spinal
Marrow; and on the same occasion noticed, that in this
view the Dorsal Vessel, the fluid of which appears to
be prevented only by the continued pulsation from
becoming solid, (which, according to Serres, it does
when acted upon by Muriatic Acid or Galvanism,)
inay be considered as a prototype of the central Ner-

278

vous System. But that the Dorsal Vessel is actually
in point of function a Brain and Spinal Marrow is as
little to be concluded from these propositions as that
when, for instance, we viewed the black spot in the
compound Eye of Insects as a prototype of the pupil,
(§. 117.) we should therefore necessarily conclude that
it actually was a pupil. Nor is it hereby rendered
less untenable that the Dorsal Vessel should be deve-
loped in the series of Animals so as to form the Heart
or Aorta, unless we should be content to range the
organization of Insects below that of Worms. (Com-
pare Meckel’s Arcliiv. b. i. h. I, s. 15.)

B. Vascular System in Animals with Spinal Marrow

and Brain.

§. 697. The Vascular System of the four superior Classes*
of Animals is distinguished from that of the inferior in the
same manner as the Nervous System; viz. partly because
being essentially subservient to the successive change of
materials, it attains a higher and more absolute degree of
centricity, these Classes all agreeing in possessing a single
Heart, an organ which presents the highest point of deve-
lopement of the Vascular, as the Brain does of the Nervous,
System; and which, consequently, exerts the same influence
over the system to which it belongs, as the Brain does over
the Nerves: partly, because the position of this Heart is
regulated nearly as much by the situation of the nervous
central organ as by that of the respiratory organs, the
Heart corresponding to the former in this respect, that inva-

279

i'iably in the lower Classes, and in the foetal state of the
higher, it is situated at a point of the anterior surface corres-
ponding to that of the posterior, where the Brain presents
itself.* This whole division of the Animal Kingdom is
farther distinguished by the red colour of the blood, and in
the two higher Classes by its considerable warmth; and
farther, in this respect also, that the Vascular System, in
addition to the circulation through the respiratory organs,
which existed even in some of the inferior Animals, pre-
sents a partial circulation through the Liver, where the
venous blood returning from the assimilative organs is again
distributed, (precisely as all the venous blood was distri-
buted through the respiratory organs in the Mollusca,) and
thence again conveyed into the common Vena Cava.
Lastly, we find also a perfectly distinct Lymphatic (absor-
bent) System, containing a clear fluid representing that in
the vessels of the inferior Classes. The general type, how-
ever, undergoes many variations and gradual approxima-
tions to completeness in the individual Classes, which we
shall next proceed to consider.

1 Section- I. Vascular System in Fishes.

(a.) Blood-Vessels.

§. 698. The circulation of the Blood in Fishes may be
compared with that of some Worms, e. g. the Earth-worm,

• Where the Brain bends forward so as to occupy the upper point of the
body, the heart is necessarily placed below rather than in front of it.

280

(j. 693.) in so far as here, also, the veins are collected on
the abdominal side, where they pour their blood into the
Heart, from which it is then propelled round the (Esophagus
through numerous circles of vessels* ramified on the bran-
chial arches, and thence again returned to the commence-
ment of the Aorta. Consequently, as the Heart here
propels the blood immediately into the Gills, it has often
been considered as merely pulmonary ; but with as little
reason as if, when an arterial trunk is tied, and the circula-
tion kept up by collateral branches, we should consider as
Arteries those lateral ramifications only which arise above
the ligature, and view those which carry the blood into the
trunk below as V eins. Consequently, as other anatomists
have already remarked, the Heart of Fishes, as is invariably
the case when there is but one, is Aortal : it is remarkable,
however, that the blood is here oxygenated in ramifications
of the Aorta itself. In the Osseous Fishes the Heart is
situated in the laryngeal region, immediately below the
head, and external to the thorax formed by the branchial
arches and their muscles: it is contained within a delicate
Pericardium, which forms a duplicature with the Peritoneum
inferiorly, by which the Heart is separated from the abdo-
minal viscera, and particularly from the neighbouring Liver.
(Tab. IX. fig. XVIII. a.) The size of the Heart is here
so inconsiderable, that, according to Tiedemann,! it is
but from 7jT to of the weight of the body, whilst in
Man it is ; which, on the one hand, well agrees with
the smallness of the Brain, (though the Heart is never-
theless ordinarily much larger than the Brain, — in the
Sturgeon more than a hundred times,) and on the other, b

• These circles of vessels, which in the Amphibia are converted into a
single one, remind us of the circles of vessels in the Sepiae. (§. 691.) (

| Anatomie des Fisch-lierzens. Landslmt. 1809, 4to.

281

connected with the moderate quantity of blood and smaller
number of vessels in these cold-blooded animals.

§. 699. The Heart itself consists of an Auricle and a
Ventricle ; of which the former has but thin parietes, and
appears of a dusky colour, receiving the venous blood from
the body by several venous trunks collected in this point,
and usually situated behind the Ventricle; the latter has
thick parietes, and is generally of an oblong shape.* The
return of the blood from the Ventricle to the Auricle is
generally prevented by two semilunar valves, (Tab. X.
fig. VI. a.) and from the former it is propelled into an aortal
trunk dilated at its origin, at which point there are gene-
rally two semilunar valves, (fig. VII. a.) but in the Carti-
laginous Fishes a greater number; in the Sturgeon, for
instance, 1 have found three rows, each containing three
valves. (Fig. IV. h. i. k.) This aortai trunk divides in such
a manner that branches go off on each side to the under
part of each branchial arch, (Tab. X. fig. V.) and after rami-
fying through the Gills, re-unite at their upper part, or at
the base of the Cranium, in the commencement of the
Aorta which runs along the vertebral column. The aortal
trunk thus again formed, in the Carp immediately passes
through the hole of an inferior spinous process of the
Occipital Bone ; then, as in most Fishes, runs through the
abdomen behind the kidnies, sending off branches to the
neighbouring parts ; and, lastly, enters the canal formed by
the inferior spinous processes of the caudal vertebrae: in
the Sturgeon, on the contrary, the membranes of the Aorta
are lost under the vertebral column, and the blood passes
through a tube formed by the cartilaginous substance of
the Spine. There are deviations from this type in the
Cartilaginous Fishes, both as regards the Heart, which is

• A second and perfectly closed Ventricle has lately, but incorrectly, been
ascribed to the Heart of Fishes.

382’

generally proportionally larger than in the Osseous lashes,
and the greater number of valves; thus, according to
Tiedemann, the Raja rubus* has three valves at the venous
orifice of the ventricle, and five rows, each containing three
Valves, at the bulb of the Aorta. The Gills, too, being
placed farther backwards, (§.598.) the Heart is farther
removed from the Head, the number of circles of vessels
from the Aorta corresponding to the greater number of the
Gills, viz. in Rays and Sharks five, in Lampreys seven.
The Heart of the Lamprey has many peculiarities, being
inclosed within a perfectly cartilaginous Pericardium at
the extremity of the elastic branchial apparatus, (Tab.
VIII. fig. IV. B. 19.) and connected to it as well by a
kind of suspensory ligament as by strong tendinous fibres;
a mode of connection which exists also in other Fishes,
e. g. the Sea-Wolf and Conger Eel. HALLERf quotes
Valsalva for the existence of glands in the Heart of the
Sturgeon pouring a black fluid into the Ventricle, which
however I have not met with.

(b.) Lymphatics.

700. The absorbent vessels bringing back the fluids
from the various parts of the body in Fishes, and first
described by Hewson,^ are distinguished, according to
him, from those of Man in the following particulars :
though forming numerous plexuses, they do not present any

* I find it the same in the Heart of the Sturgeon. (Fig. IV. c.)
t Element Phys. t. i. p. 3b4.

| An Account of the Lymphatic System in Fishes. Philos. Trans. 17G9,
p. 204.

283

glands; they have not any valves, so that they can he in-
jected from the trunks, two points in which they evidently
appear to approximate to the Vascular System of the infe-
rior Classes ; in the Cod, and probably in other species, they
form a peculiar beautiful net-work between the muscular
and mucous coats of the intestine, into which the absorbed
chyle appears to be first carried ; they are united in a large
Receptaculum Cliyli placed on the right side at the upper
end of the Stomach, from which the lymph is conveyed
by plexuses, and ultimately by a fine orifice into the jugular
Vein.

Section II. Vascular System in the Amphibia.

(a.) Blood-Vessels.

§. 701. The Class Amphibia, as regards circulation*
approximates to the preceding in the following particulars :
l.s£, in the imperfect oxydation of the blood, though arising
from 9ther causes than in Fishes ; 2d, in the low tempera-
ture of the blood (cold-bloodedness); 3d, in their more
scanty and minute blood-vessels,* and the small quantity of
blood that they contain, particularly as compared with the
higher Classes, for the body of Fishes is yet more bloodless ;
and, lastly, the size of the Heart, which, though somewhat
larger than in Fishes, is still much smaller than in the

• Blumenbach f Comp. Anal. p. 234) found that in the Lacerta palus-
iria the weight of the blood was to that of the body as 24 to 30 ; whilst iii
Man it is as 1 to 5.

284.

liig'lier Classes. In the Frog, for instance, I found the
Heart and in the Coluber natrix the weight of

the body.

The circulation in Frogs is very remarkably similar to
that of Fishes. The Heart, which is situated within its
Pericardium, immediately below the Sternum and above the
Liver, is here also simple, consisting of a single capacious
auricle with thin parietes, and an elongated, red, and
muscular ventricle ; the arterial trunk immediately after its
origin divides into two branches, surrounding the (Esopha-
gus, and which, precisely like the branchial vessels of Fishes,
first unite in the lumbar part of the vertebral column in
order to form the descending Aorta. (Tab. XIII. fig. VIII.)
It is probably from the arterial circle thus formed that the
branchial vessels are given off in the Larva, and in those
Amphibia which have branchise, (precisely as in Fishes,)
and from which the Pulmonary Arteries arise as lateral
branches in the perfect animal, so that, consequently, a part
only of the blood passes through the Lungs. Swammerdam*
farther states that two Carotid-like Arteries ascending
from this circle present two grey dilated points, which
appear to indicate the situation whence the Branchial
Arteries were given off at a former period. The Venous
System here presents many peculiarities : in the first place,
there are true Pulmonary Veins returning the blood from
the Lungs to the Heart, (whilst, on the contrary, the blood
of Fishes is conveyed through the respiratory organ, and
thence into the Aorta, by Arteries alone;) they empty
themselves, however, together with the other Veins, into
two caval trunks, which open into the Auricle on each side;
secondly, (as is peculiarly evident in Salamanders,) the
Umbilical Vein, which in the superior Animals is ordina-

* Bib. Nat. a. 327, t. 49. I, however, as well as Meckel, find merely
a dilatation of each Carotid. (Tab. XIII. fig. VI. B. i.)

285

rily converted into tlie round ligament of the Liver, accord-
ing to an interesting discovery by Jacobson,* remains
pervious through the whole period of existence, receiving
the branches of the Epigastric Vein and the Veins of the
great urinary Bladder (Allantois) : an organization expli-
cable only by a reference to the mode of developement of
these Animals, (without an Umbilical Cord or Placenta,) and
proving that the surface of the skin in the foetus here forms
a respiratory membrane (Chorion,) and consequently that
the Umbilical Vein must arise from that surface as from
the Chorion in other cases, the Allantois at the same time
not projecting from out of the Abdomen, but remaining
permanently as a receptacle for water.

§. 702. The Circulation of the blood is already some-
what more complicated in Tortoises than in the preceding
Order. The Heart, situated immediately above the Liver
and close behind the abdominal scutum, consists of two
Auricles and a Ventricle, the latter being divided into
several communicating cells and presenting a broad circular
depression, having likewise strong muscular parietes, and
being connected at its inferior obtuse extremity by means
of a tendinous ligament to the Pericardium, as is the case
in many Fishes. The Auricles are extremely capacious,
either of them being nearly equal in size to the Ventricle :
they are divided by a septum, which, however, is perforated
in ttyi Testudo scorpioidcs; and we find that, as in Man,
the right receives the blood of the body by means of the
Vense Cavte, whilst the oxidised blood from the Pulmonary
Veins enters the left by a fissure-like valvular orifice. The
internal arrangement of the Ventricle varies somewhat in
different instances : in some, e. g. the Testudo grceca , it is
little more than a simple cavity rendered irregular by the

* Bulletin des Sciences de la Snc. Philnm. 1813. Those investigations
also show that the urine is in part secreted by inferior Renal Veins.

280

projecting bundles of fibres of its parietes : in others, on
the contrary, e. g. the T. imbricata , these fibres are so very
prominent, and appear to divide the cavity so completely
into several cells, that Mery* was induced to admit the
existence of a Ventricle for the Pulmonary Artery and
Aorta, in addition to a right and a left Venticle. Whether
the cavity, however, be simple or complicated, the course
of the blood through the Heart is always such that the pul-
monary blood enters at the left side, is mixed with the
blood of the Venae Cavae rather towards the back part of
the Heart, and then passes on the right side into the Aorta,
and anteriorly into the Pulmonary Arteries. (See Tab.
XIII. fig. V.) The Arteries here again form a circle
round the CEsophagus, which we must consider as a repe-
tition of the Branchial Arteries : the Aorta, which in the
T. imbricata is furnished with two semilunar valves, arises
double from the right side of the Heart, a branch ascending
from the division to form the Axillary and Carotid Arteries,
whilst the two great lateral trunks bend outwards right and
left: the left, after giving off some branches to the Intestinal
Canal and Liver, unites on the vertebral column with the
right and larger branch, forming with it the descending
Aorta which supplies the other parts of the body, a vascular
circle being thus produced precisely as in the Frog. A
second circle, as has been proved by the observations of
MECKELf and Munniks, is formed by the Pulmonary
Artery, which, like the Aorta, is furnished with two semi-
lunar valves, and immediately after its origin divided into
a right and left branch, each of which enters one of the
Lungs, but, at the same time, communicates with the cor-
responding branch of the Aorta by means of an arterial
canal (Ductus Botalli), which, probably, is permanently
* M&moires de 1' Academic des Sciences. 1703.
f Notes to Translation of Cuvier, vol. iv. p. 130.

287

pervious. As a consequence of these dispositions, but a small
part of the blood is exposed to the action of the atmosphere,
and the oxydation of the blood woijld be even less perfect
than in Fishes, where all the blood passes through the Gills,
were it not that in the latter the Respiration is merely of
water, and that probably in these and other Amphibia
there is, in addition to the pulmonary Respiration, a respi-
ration of an aqueous kind performed by the permanently
existing Allantois. As to the Veins, it is remarkable that
here, according to the investigations of Bojanus* and
myself, the blood of the whole posterior part of the body,
the abdominal coverings, posterior extremities, &c. (with
the exception of the venous trunk belonging to the Kid-
nies and Sexual Organs,) probably in the same manner as
in Frogs and Salamanders, is carried into the Liver, and, as
I find in the Mud-Tortoise, by two trunks, in order to
circulate partly in this organ, and partly, according to
Jacobson, by means of inferior Renal Veins, in the Kid-
nies, previous to arriving at the Fleart. The venous blood
of the body, as well as that of the lungs, is collected into a
venous receptacle for each close to the Auricles, which it
then enters in the manner already described.

703. In Serpents, the Heart is situated towards the
middle line of the body, in front of the Lungs and above
the Liver ; and in the Coluber natrix , about 4 inches below
the head. Here, also, it is furnished with a left Pulmo-
nary Auricle and a right caval, which is nearly as large
again : both open into the simple and fleshy oblong V en-
tricle, from which arise a double Aorta, the branches of
which meet again on the vertebral column, and a single
Pulmonary Artery. As to the Veins, in those Serpents
where the Lung is single, there is but one pulmonary
Vein: there are, also, a Vena abdominalis proceeding to
* Oken’s Isis, b. i. Ji. vii. s. 879.

288

the Liver, and two Inferior Renal Veins, which last, how-
ever, are in this case unconnected with the former.

§. 704. In Lizards, the structure of the Heart again
offers a great similarity to that of Tortoises. Hence, con-
sequently, we find two separate Auricles and a single Ven-
tricle, which, however, is generally divided into several
cells. In several species, e. g. the Crocodile, the Heart is
even, as in some Tortoises, attached by a tendinous ligament
to the Pericardium. (Tab. XII. fig. XIX. i.) The situation
of the Heart is here again usually immediately above the
Liver; though, according to Cuvier, in the Iguana at a
considerable distance from it, and quite in the front part of
the Thorax. Its Auricles (fig. XIX. g. h.) are propor-
tionally smaller than in Tortoises, and separated by a thin
septum, which is perforated in the Lacerta apoda. The
Ventricle, the form of which is tolerably similar to those
of the human heart, is divided, in the Crocodile, into three
anastomosing cells in such a manner that the blood of the
Venm Cavm passes from the right Auricle into the two
inferior cells on the right side, from which the pulmonary
Artery and left ascending Aorta arise ; whilst, on the con-
trary, the pulmonary venous blood flows from the left
Auricle into the left superior cell, which is more distinct
fiom the other two, and which gives origin to the right
Aortal, Carotid, and Axillary trunks: the latter vessels,
consequently, are not only filled by blood that is more
©xydised than that of the left Aorta, but also contain a
smaller proportion of venous blood than the Arteries of
Tortoises, inasmuch as but little blood penetrates this from
the other two cells. The right and left Aorta, the hitter of
which is reduced in size by giving off several considerable
branches, unite on the vertebral column, so as to make the
usual vascular circle around the (Esophagus, and then form
the descending Aorta, the remaining course of which

289

presents nothing peculiar. The Veins of the body do not
appear to differ essentially from the ordinary arrangement
found even in Man, except so far as regards the distribution
of the Veins of the Liver and Kidnies, already noticed.*

• According to Mr. N. M. Hentz, the American Alligator (Crocodilus
lucius ) presents a much more perfect structure of the Heart than any other
of the Amphibia, the two Ventricles not having any immediate communi-
cation. From his description the following particulars are derived : — The
Vena Cava Superior follows the course of the right Subclavian Artery in its
passage through the chest, and descends to the Pericardium to join the Vena
Cava Inferior opposite the right Auricle. In its course upwards, the Infe-
rior Cava runs upon the right side of the spine until it reaches a straight
channel in the substance and near the edge of the Liver, where it receives
four or five vence cavae hepaticae. A Vein analogous to the right Subclavian
enters the upper part of the right Auricle at its left side. The auriculo-
ventricular opening of the right heart is furnished with two valves. The
right Ventricle opens into two arterial tubes, of which one is the Pulmonary
Artery; the other, at the left and upper part of the Ventricle, is furnished
at its base with two semilunar valves, and terminates in the left Aorta.
There is not any direct communication between the cavities of the two Ven-
tricles. The left Ventricle, which is rather smaller than the right, and
situated behind and somewhat above it, has also two valves at the orifice by
which it communicates with the Auricle. Like the right Ventricle, also, it
opens into two arterial tubes, of which the first leads into the left Aorta, and is
separated from the corresponding orifice of the right Ventricle by a cartila-
ginous septum only. It is important to observe, that this septum interrupts
the immediate communication between the cavities of the two Ventricles,
(for they communicate intermediately by means of the Artery from each open-
ing into the left Aorta,) and constitutes the most essential variation of the
structure of the Heart in this, from what is found in other Saurian Amphibia.
This first branch, arising from the left Ventricle, is bordered by a valve at it*
origin that nearly closes its cavity. The second artery from the left heart
divides shortly after its origin into three branches, of which one is the right
or systemic Aorta, the second the right Subclavian, and the third the com-
mon trunk of the Carotid and left Subclavian Arteries. The left or
splanchnic Aorta, previous to dividing among the viscera, gives off a large
branch which communicates with the right, descending, or systemic Aorta.
The three great Arteries, viz. the Pulmonary, and right and left Aoit3, ora
closely connected together immediately after their origin, and dilate into ex*
pensions which are collectively larger than the cavities of the Heart. In the

VOL. II.

290

(b.) Lymphatics.

§. 705. According to Hewson,* the Lymphatics of
the Amphibia differ from those of Fishes in being provided
with Valves, though they are neither so close together nor
so strong as in the higher animals, being insufficient to
prevent the course of injections from the trunks to the
branches. In a Turtle which I examined with respect to
this point, there were numerous ramifications of the Lym-
phatics between the muscular and mucous coats of the
Intestine, though rather having the appearance of cells
crowded together. The Lymphatics of the whole of the
lower part of the body united in a common receptacle,
from which there did not proceed any single Thoracic
Duct, but a double Plexus connected superiorly with the
cervical Plexus, and emptying itself into the Axillary Veins
by two branches on the right, and one on the left side.f

common state of circulation the blood passes from the right Ventricle chiefly
into the Pulmonary Artery,' and partly, also, into the branch arising from it,
to enter the left Aorta. The blood of the left Ventricle, on the other hand,
is thrown into the right Aorta, right Subclavian and Carotid Arteries, a
small quantity only passing into the left Aorta. When the animal is under
water, the action of the lungs being interrupted, and the circulation of blood
through them suspended, a larger proportion of the contents of the right
Ventricle must pass into the branch of communication with the left Aorta,
and it is probable, that under such circumstances only does it happen that
the blood sent to the various organs is an admixture of arterial and venous
blood, as in the Chelonia and other Sauna. ( Edinburgh Journal of Med.
Science, i. 217.) — Translator.

* An Account of the Lymphatic System in Amphibious Animals, in Phil.
Trans. 1769. p. 178.

f In the Crocodile Hewson found the Chyle white, whilst in Fishes and
other Amphibia the contents of the Lymphatics are usually colourless.

291

Section III. Vascular System &f Birds.

(a.) Blood-Vessels.

§. 706. The extended Respiration of this Class, and the
distinguished developement of its Muscular System, which
we have observed in so many particulars, are closely and
essentially connected with a corresponding degree of per-
fection in the formation of the Vascular System. We
here, for the first time in the animal series, meet with warm
blood, and also perfectly distinct Pulmonary and Aortal
Hearts, connected together, however, so as to form a single
organ. Hence, consequently, not a part merely, but the
whole of the mass of fluids is exposed to the action of the
air, and that even in two ways, once in the Lungs, and
again in the air-cavities of the other parts of the body.
We are enabled, notwithstanding, to trace the transition in
the form of the Heart and the distribution of the Vessels
from those of the preceding Class, and particularly of
Lizard^. If, for instance, in the Crocodile, (§. 704.) we
suppose the incomplete Septum between the double right
and the left Ventricles (Cells) to be perfectly closed, —
viewing that branch of the Aorta which gives off the Ca-
rotid and Axillary Arteries as the sole Aortal trunk, and
instead of the Pulmonary Artery and left Aortal, (which
latter is, in fact, merely an accessory branch,) imagine that
the former alone arises from the right Heart, — we shall
then have a perfect idea of the Heart of Birds, and shall
find that here, for the first time, (at least, in the fully

u 2

292

formed animal,) there is not any vascular circle around the
CEsopliagus. It exists, however, in the Embryo, for, as
was remarked by Haller, the two Pidmonary Arteries
enter the Aorta as Arterial Ducts, (the abdominal Aorta
being, consequently, formed by three roots, the proper
Aorta and the two Arterial Ducts,) and in that way sur-
round the CEsopliagus, (Tab. XVI. fig. XIII.) ; whilst
the proper Pidmonary Arteries are sent off laterally as
branches, nearly in the same manner that the Pulmonary
Arteries of the Frog are given off from the aortal circle.

§. 707. The Heart in Birds is placed within its Peri-
cardium in the middle of the upper part of the Thorax,
immediately above the Liver (Tab. XV. fig. XI. e.), be-
tween the Lungs, behind the Sternum, and with its point
a little turned to the right side in those that have power-
fully muscular stomachs : in Accipitrine Birds, some
Gallae, and also, as I observe, in the Green Parrot, it is
quite in the middle. Its shape is conical, its colour dark
red, and its parietes, particularly those of the left Ventricle,
extremely strong and powerful. Its bulk deserves parti-
cular notice, being greater in proportion to the rest of the
body than in any other Class: its weight, according to
Tiedemann,* being to that of the body from ^ to
and thus forming a remarkable contrast to the proportions
found in Fishes and Amphibia. Its internal organization
approaches very closely to that of the Heart of Man : it
consists of two Ventricles, and two thin, but tolerably
muscular, Auricles, of which the right is the largest. The
left Auricle receives the blood from the Pulmonary Veins,
(its return being prevented by a Valve,) and empties it
into the left Ventricle, which may be considered as the
principal part of the Heart, the right Ventricle being
applied to its side like a shell. The reflux into the Auricle

* Zuoloyir, b. ii. s. 562.

293

is prevented partly by a kind of Sphincter Muscle, and
partly by a membranous valve with tendinous fibres attached
to it, and corresponding to the Mitral Valve of the human
Heart. The left Ventricle elongated, capacious, and dis-
tinguished by the strength of its muscular parietes pours the
blood into the Aorta, which is furnished with three semi-
lunar Valves at its root, and divides immediately into three
branches.

§. 708. The right Heart has, also, an Auricle into which
the blood of the body is conveyed by two Vense Cavse, of
which the upper has one, and the lower two, Valves. It is
somewhat more capacious than the left Auricle, and opens
into the right Ventricle by an orifice furnished with a
peculiar broad and fleshy Valve attached to the side of the
cavity. The right Ventricle is shorter and more com-
pressed than the left, and, as already mentioned, is disposed
concentrically around its right side. The Pulmonary
Artery, provided with three Semilunar Valves, arises com-
pletely from its left side, and immediately after its origin
divides into two lateral branches, its trunk being narrower
than that of the Aorta.* (See Tab. XVI. fig. XIV.)
The Arteries themselves have very thick coats, and their
fibrous structure is very distinct. Their course in general
is perfectly similar to that described in human Anatomy ;
though I must mention, that of the three principal divisions
at th^ commencement of the Aorta, the right forms the
ascending Aorta, the middle one the right, and the last the
left, Subclavian Artery, from which last the Carotid and
the large Vertebral Arteries arise on each side, the trunk
continuing its course to the wing as the Axillary Artery.

* In contradiction to thi6 observation of Cuvieh’s, which agrees with my
own experience, Tiedemann states, that the injected Pulmonary Artery
appears to him larger than the Aorta, which, however, probably depends on
the weaker parietes of the former yielding more to the force of the injection.

294

The Aorta here does not divide at its lower part as in Man,
but gives off a Femoral Artery on each side, and then
descends, as an Arteria sacra media, to be distributed in
the Pelvis. As to the Veins of Birds, their parietes are
thicker than in other animals, and their fibrous structure
is easily detected in large individuals. As regards their
course, the considerable capacity of the three inferior Caval
trunks, already noticed, which Cuvier and Meckel have
observed in Diving Birds, is physiologically important in
so far as explains the long continued interruption of Re-
spiration to which these Birds are capable of submitting,
and reminds us of similar receptacles on the principal
venous trunks of Tortoises. (§. 702.) Jacobson has here,
also, discovered the distribution of the greater part of the
venous blood of the posterior part of the body partly
through the Liver, and partly through the Kidnies.

(b.) Lymphatics.

§. 709. The Lymphatics of Birds were first discovered
by J. Hunter, and afterwards more precisely described
by LIewson,* who found the following peculiarities in
them: — 1st, A transparent colourless Chyle, which, how-
ever, does not coincide with the fact that the blood of
Birds often presents an intermixture of a perfectly milky
fluid ; 2d, an absolute deficiency of glands in the abdo-
men and about the thoracic duct, a few only being found
in the neck ; 3d, the frequent varicose dilatations found
in then?, if? indeed, this be not rather the consequence of
domestication and more of a diseased state. The Lymphatic

* An Account of the. Lymphatic System in Biids. Philos. Trans. 1768.
Hai/leh, indeed, (jiiotessome ancient observations of Lymphatics in Fishes,
Amphibia, and Birds, but without attaching any ciedit to them..

295

Vessels in Birds are collected into a large Plexus in the
region of the Coeliac Artery, thus supplying the deficiency
of a receptaculum, and having two thoracic ducts ascending
from it to empty themselves into the Subclavian Veins.
According to Tiedemann, the lymphatic glands of the
neck are more developed in Wading and Aquatic than in
Land Birds.

Section IV. Vascular System in Mammalia .

(a.) Blood-Vessels.

§. 710. Both as regards the distribution of the Vessels
and the form of the Heart, the structure of the whole Class
so closely corresponds to the human type, that it is neces-
sary to notice only a few peculiarities of individual Species,
which present deviations from the ordinary forms, and in the
same degree approximate to the inferior formations. In this
respect we have to notice particularly the Amphibious and
Cetaceous Mammalia : first, on account of the very great
quantity of blood, (in which Hunter* even suspects the
existence of an unusual number of globules,) and also on
account of the peculiar structure of the Heart, and the large
and very much divided vessels; points in which we again
find the predominance of the Vegetative Sphere, as in-
stanced likewise in the length of the intestinal canal, the
number of stomachs, collection of fat, &c. Hunter, for

* On the (Economy and Structure of Whales. Philos. Trans. 1787, p.
413.

20 f>

instance, found the Aorta of a White Whale a foot in dia-
meter, and observed also numerous arterial plexuses between
the Ribs, about the Vertebrae, &c. which appeared to have
the character of mere receptacles of blood. Even at the
origins of the Aorta and Pulmonary Artery there are fre-
quently dilatations,* which, even if they are not to be con-
dered as parts of the normal structure, still appear to be
rendered compatible with health by the mode of life and
general organization of these Animals; whilst in Man, on
the contrary, they form dangerous diseases (Aneurysm).
The same remark is also applicable to the dilatation of the
venous trunks, to be hereafter noticed, and to the varieties
in the structure of the Heart, which in Man produce incon-
venience and disease. The very flat and broad shape of the
Heart in the Amphibious Mammalia (Tab. XX. fig. VII.
a.) is remarkable from its coincidence with the form of the
Heart in Tortoises, (§. 702.) as well as in the human
embryo. The point of the Heart is double here, in
the Manati for instance, the left point projecting on
account of the greater length of the left Ventricle, in the
same manner that in Birds we found the left longer than
the riofht \ entricle. There is not the same difference here

between the thickness of the aortal and pulmonary Ven-
ticles as in Man and other Mammalia ; and, consequently,
the latter is in proportion more muscular. In these species,
and also in some other Diving Animals, e. g. the Beaver
and Sea-Otter, we occasionally find the Foramen Ovale
in the Septum of the Auricles open,f and less frequently
the ductus arteriosus between the Aorta and Pulmonary
Artery: a structure, however, which cannot with constancy
or propriety be connected with the mode of life of these

* Meckei., Notes to Cuvier's Comp. Anat. vol. iv. p. 77.
f tiie va.ious testimonies to this effect collected by Meckel, loot
til. p. 37.

297

animals, inasmuch as that here, as well as in other Mam-
malia, it belongs properly to the period of foetal existence.
The position of the Heart of the Whale varies less from
that of Man than in other Mammalia, the pericardium,
according to Hunter,* being attached by a broad surface
to the diaphragm. As regards the distribution of the
vessels, we may remark that the Aorta, in consequence of
the imperfection of the posterior extremities, is continued,
as in Fishes, and even in Birds, below the caudal vertebrae,
in the form of an Arteria Sacra Media, having previously
given off two branches analogous to the Iliac Arteries. A
peculiarity of the inferior Vena Cava in the Porpoise and
Seal deserves notice, viz. that it forms a considerable dila-
tation between the Liver and Diaphragm, thus representing
a similar structure in Tortoises and Diving Birds. (§.708.)
A similar dilatation has been found also in the common and
Sea Otter.f |

§. 711. The Heart and Vessels in other Mammalia
agree still more completely with those of Man. The most
remarkable peculiarities are, first, as regards the Heart:
except in the most anthropomorphous Apes, it does not
reach the Diaphragm, its point resting on the Sternum,

* Loc. citat. p. 41 4.

f It is remarkable that in the Ornithorhvnchus, which dives admirably.
Home /Phil. Trans. 1802, p. 74) could not discover any communication be-
tween' the right and left Hearts, nor does he notice any venous dilatation of
this kind. He says merely that the right Auricle is very capacious.

f The Heart of the Dugong is very remarkable for the complete separation
of the two Ventricles, which come in contact with each other merely for an
inconsiderable extent at the upper part, thereby presenting the real character
o/ the central apparatus of circulation, as being formed by thejuxta-position of
two actually distinct organs. The structure of the Heart does not, however,
vary in any essential particular from that common to other Mammalia. The
Foramen Ovale was found perfectly closed in the young animal. (Home,
Phil. Trans. 1820, p. 11.) — Translator.

298

besides that it is situated in the middle line of the body,
and not, as in Man, turned to the left side. In the latter
particular, however, I find a remarkable exception in the
Heart of the Mole, which is very much directed to the left
side; a position that, taken generally, is probably not with-
out importance, and appears to prove that Assimilation
predominates on the left as Respiration on the right side,
the Lungs and Heart bearing the same proportion in the
Chest as the Liver and Stomach in the Abdomen. According
to Cuvier, the Heart in the Elephant is broad and thick,
like that of the Porpoise ; a proof, with many others, of the
relation existing between the Pachydermata and Cetacea.*
As relates to the internal structure of the Heart, we may
remark that the right Auricle in many instances, precisely
ns in Birds, (§. 708.) receives two superior Venae Cavae,
c- g. in the Porcupine, Guinea-Pig, Kanguroo, and, accord-
ing to Home, the Ornithorhynchus ; also, that the Eusta-
ehian Valve, which in Diving Animals, e. g. the Seal, is
very strong, is wanting in many species, e. g. Lions, Bears,
and Dogs. The ossifications naturally existing in the Heart
of many Ruminants, and of the Pig, are also remarkable,
inasmuch as ossification of the same parts is frequently
the effect of disease in Man. In the Stag they are cruci-
form, and are placed at the origin of the Aorta in the
Septum of the Ventricles. They appear to be formed from
about the third to the fourth year of life, are less perfect
in the female, and altogether wanting in the Roe and Fal-
low-Deer.fi In what concerns the remaining vessels, there

* In this respect the tendency to dilatations of the Aorta in the Peccari
is also remarkable, having been described there as the natural state, (Dau-
eenton in Buffon’s Hist. Nat. t. x.) particularly as similar dilatations fre-
quently occur in the Cetacea.

f Diss. in. sistens Observ. uonnullus Zoolom. Os Cordis Ccrvi , Clavi-
r.ula frlis, Sfc. spedutUcs. Fites. C. F. J. Kii'LMEYEit. resp. Luethi.
Tubing. 1814.

299

deserve notice several peculiarities in the brandies arising
from the arch of the Aorta, which occasionally present
themselves as varieties in Man ; also, and particularly in
loner-tailed Animals, the continuation of the Aorta below
the caudal vertebrae, as in the preceding Classes; and, lastly,
several peculiar reticular ramifications of vessels. Of the
latter we have an instance in the Rete Mirabile, already
noticed, (§. 328.) at the base of the Brain. Of the same
nature, also, are the plexuses formed by the Arteries for the
extremities in the Sloths and Lories, and from which they
again emerge to form new trunks, nearly in the same man-
ner that the Aorta in Fishes is formed by the branchial
vessels, or the Nerves of the extremities by their Plexuses.
The number of these longitudinal branches collected into
bundles is very considerable in the Axillary Artery, and is
most so in the Three-toed Sloth, where they amount to 34
in the posterior, and 62 in the anterior, extremity. The
discoverer* of this singular structure has correctly deduced
from it the power these animals possess of remaining long
in one position, as well as the tardiness of their muscular
motion. The fact remarked by Saissy,! of the proportion-
ally greater size of the superficial vessels in hybernating
Animals, is so far remarkable, as, in connection with the
want of coagulabilityin their blood, it serves to elucidate
their state of torpidity. The most important peculiarities
of the Veins have been already noticed, such as the dilata-
tions ot the inferior, and the existence of two superior,
Venae Cavse : to which we may add several venus Plexuses,
e.g. the very delicately interwoven venous rete (rete mirabile
venosum) on the Horse's foot, and also the large and much

* Carlisle, Account of a Peculiarity in the Distribution of the Arteries
sent to the Limbs of Slow-moving Animals. ( Philos. Trans. 1800 and 180 k)

f Recherches Experimental sur la Physique ties Animau.z Mammiferes
llybcrnans. Paris, 1808.

300

ramified venous trunks on the uterus of several pregnant
Animals, e. g. the Cow.

(b.) Lymphatics.

§. 712. It is well known that human is indebted to
Comparative Anatomy* for the discovery of the Lymphatic
System, as well as for many others : it is favoured in Mam-
malia by the distension of the proportionally larger absorbent
vessels of the Mesentery with milk-white Chyle, thus ren-
dering them more distinctly perceptible. This greater size
of the trunks of the Absorbents is one of the principal points
serving to distinguish the system in Mammalia from that of
Man, but few variations having been hitherto discovered in
the course of the branches. A deviation of that kind, and
at the same time an approximation to an inferior type, con-
sists in the smaller number of Lymphatic Glands generally,
and of those of the Mesentery in particular ; of which last
Cuvier remarks, that in Herbivora, with a long intestinal
canal, they are more separated, and in the Carnivora more
crowded together, and collected in larger masses. The
structure observed by Abernethy-)- in the Mesenteric
Glands of the Whale deserves particular notice, and above
all a repetition of the observations. He states that in these
animals after injection there appear not glands but cavities
in the Mesentery, into which open not only the Lymphatics
of the Intestines but also Arteries and Veins, so that a mix-
ture of the Chyle with secretions from the Arteries, and at
the same time the passage of the former direct into the

* They were seen in the Mesentery of the Goat even by Eracistratus
and Galen.

f Philosoph. Trans. 1796, p. 27.

301

Veins, are rendered possible. As to the Thoracic duct,
there are usually two, as in Birds ; whilst, on the contrary,
in the higher species, and in Man himself, there is but a
single one, and that on the left side, as the situation more
particularly devoted to the assimilative apparatus.

It will be seen that there are not any peculiarities of
structure that can be pointed out as exclusively belonging
to Man in the Vascular System, — the central System of
Vegetative Life ; on which subject we may again refer to
the remarks already made. (§. 683.)

BOOK II.

DESCRIPTION OF THE ORGANS SUBSERVIENT
TO THE REPRODUCTION OF THE SPECIES;

AND

also of the developement of individual

ANIMAL ORGANISMS.

713. In the Vegetable World we find the great object
of Nature, the continuation of the Species, effected in two
Wa)rs : in one, the mother plant throws out from Buds
(they may appear also as Tubera or Bulbs), Shoots, which,
gradually becoming detached, continue to live as new and
perfectly distinct individuals: in the other, two different
tendencies existing in the Plant appear definitely fixed in
organs of opposite natures, i. e. as Stamina, (positive,
animal,) on the one hand, and on the other a Pistil, (nega-
tive, purely vegetative,) which by their mutual and com-
bined influence communicate to the Bud (Seed), contained
within the Pistil (vegetative organ), the power of reproducing
in itself the whole Plant. Kieser,* to whom we are
indebted for having thoroughly established the identity of

* Grundzugc dcr Anat. d. Pjianzm, s. 192.

303

character of Buds, Bulbs, and .Seeds, says of the Seed,
“ It is the Bud in a state of greater perfection, but at the
“ same time more compressed within itself, having more of
“ individuality, and, consequently, an independent exist-
<£ ence. The whole Plant is contained preformed within
<£ the Seed, in the same manner as within the Tuber, Bud,
££ or Bulb, but, at the same time, so far ideally, that it fre-
£C quently is scarcely perceptible as a material embryo.”
The whole of this is repeated most perfectly in the Animal
Organism. We shall find Animals in which propagation
is effected by the detachment of individual Shoots, (in
which a part of the maternal body appears as a material
embryo,) or even by the division of the maternal body into
several parts : whilst, on the contrary, in other species, dif-
ferent kinds of organs, usually placed in distinct bodies,
present themselves, being either of a vegetative (female)
or of an animal (male) character, and by their combined
action impart to a mass of elementary matter, originally
proceeding from the vegetative organ, the power of repro-
ducing within itself the collective animal organism; i. ei
give to it the character of an Ovum, in which, as in the
Seed of the Plant, and even more so, the embryo exists
merely ideally, and is produced materially only by the
accession of certain external circumstances. But as the
Seed in Plants is not always the product of the combined
action of the Stamina and Pistil, being frequently, as in
Fungi, Lichens, &c. formed by an organism in which we
do not discover this contrast of organs, and which on that
account appears 'more purely vegetative ; so, also, in Ani-
mals the formation of Ova very commonly occurs as the
product of a body in which we cannot detect the distinc-
tion of male from female organs, and which, therefore, has
more the appearance of being purely female. But, lastly,
since Animal as well as Vegetable Organisms are not pro-

304

duced solely from other similar ones, but also from elemen-
tary materials, either primarily, or secondarily by the death
or disintegration of other Organisms, we may with propriety
arrange the various modes of origin of Animals in the fol-

lowing tabular form.

§. 714.

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305

But, as the different modes of developement of Plants
are ultimately referrible to one and the same, so, also, are
these various modes of Generation of Animals : of which
we shall be easily convinced, when we consider that Sexual
Generation approaches to Generation without Sexes, inas-
much as in the former case the Germ to be impregnated
belongs to the vegetative female organ, and that the Ovum
is produced like a Shoot from it; in which way, also, Ge-
neration without Sexes approaches to Propagation by
Shoots, and this again to Propagation by Division, viz.
inasmuch as the Shoot is originally an integral part of the
maternal body : whilst, ultimately, the origin of all these
modes of Generation is deducible solely from the re-pro-
duction of organic elementary matter.

Nevertheless, we shall find these divisions useful in the
following considerations, in which we shall again find that
the simplest modes of Generation are proper to the lowest
Classes, and that in the superior, on the contrary, we meet
with sexual Generation, and that again with very various
modifications.

This Book we shall again subdivide into two Chapters,
considering in the first the Organs destined for the pro-
duction of new Organisms, (with which the Sexual Sense
is connected in the same manner as the Sense of Taste
with the Digestive Organs;) and in the second, the deve-
lopement of those Organisms themselves.

VOL. II.

30G

Chapter I. Of the Sexual Organs.

§. 715. From the circumstance that the Sexual Function
consists essentially in an excretory action, it is to be ex-
pected that the Organs subservient to it should, as far as
concerns their excretory nature, agree in many points with
the Secretory Organs we have already examined. Like
them, therefore, though not in the same manner devoted to
the support of the individual, they belong to the class of
vegetative Organs ; like them, they are principally con-
nected with the Intestinal Canal, (particularly its inferior
and chiefly excretory parts,) and closely related to the
respiratory organs ; nay, the Sexual Organs, particularly
the male, appear as exclusively secretory organs, approxi-
mating in that respect to the respiratory organs; whilst the
female, on the contrary, from their formation into cavities
and their nutritive activity, present a closer relation to the
Digestive Organs. Lastly, we very frequently find pecu-
liar secretory organs connected with the Sexual, of which
the Urinary System, already considered, forms an instance
in the Superior Classes.

A. Sexual Organs in Animals without Spinal Marrow

and Brain.

Section I. In Zoophytes.

§. 716. Distinct Sexual Organs, as well as those for so
many other functions, are wanting in the lowest Species of

307

this Class: nay, as concerns the Infusoria, they appear to
originate without Sexual Generation, by the division and
detachment of individual parts of the body ; modes of
origin in which genital organs are not required. Polypes,
as well those that are uncovered, as those that inhabit
Corals, propagate either by separation (Shoots) or by the
formation of Ova without Sexes ; a distinction which (in-
asmuch as Shoots and Ova are essentially identical, §. 714.)
is founded on the fact that the Shoot originally protrudes
in the form of a Bud, (Tab. I. fig. I. a.) from the external
surface of the body (which here, probably, forms the first
respiratory organ) ; is gradually developed into a new
animal, (fig. I. b.); and is then detached, both animals
existing permanently distinct; a mode of Propagation
which may be observed particularly in Fresh-water Polypes.
The Ovum, on the contrary, is rather evolved from the
Intestine and then thrown off in the vicinity of the mouth,
as is usually the case in the Gorgoniae; whilst, on the other
hand, the Polypes of Sponges expel their Ova through the
mouth itself. (Fig. VIII. C.) The capsule-like Ovaries
of the Sertulariae are particularly deserving of notice from
the very evident imitation they offer of the Seed-Capsules
of Plants. (Fig. VII. B. a.)

§. 717. In all the species of Medusae and Echinodermata,
propagation appears to be effected by Ova without Copu-
lating, (Generation without Sexes,) unless, indeed, it should
happen that there is single Hermaphrodite Copulation in
some, e. g. the Holothuriae. In the Medusae, according to
Gaede,* the Stomach has little folds in circles, in which
the ova are probably first formed, but are then thrown off,
remaining some time in the margins of the arms,f increas-

• Beyiriige zvr Anat. u. Phys. d. Medusen, s. 19.
t This transference of the young from an internal organ (in this case,
the Stomach) to an external (the Skin) is physiologically very remarkable.

308

ing- in size, until they are sufficiently advanced to be
detached and exist permanently distinct. (Tab. I. C. D.)
According to Spix,* the cavity of the Stomach in the
Actiniae is surrounded by several grape-shaped Ovaries,
the ducts of which gradually unite together and terminate
by several apertures in the Stomach ; the Ova, consequently,
like the undigested food, (§. 434.) being expelled through
the mouth. (Tab. I. fig. X. A. B.) He states, also, that
there are similar globular Ovaries under the lobes of the
Liver (§. 643.) in the rays of the Asterias. (Fig. XI. C.)
More than this, however, most Polypes, as has been suffi-
ciently proved by the experiments of Tremble y, are pro-
pagated by division into several parts.

Section II. Sexual Organs in the Mollusca.

(a.) Acephala.

§. 718. In this as well as in the following Order the
Sexual Organs, particularly the most essential, the Ovaries,
are usually placed in the vicinity of the Liver and Lungs,
or Gills, a position which forms an additional instance of
the relation existing between the Sexual, Respiratory, and
Secretory Organs. In the Acephala, more particularly,
as in the higher Species of Zoophytes, there is not any

and is frequently repeated in the superior Classes, even in Man, by the
nutrition of the new being, first in the Uterus, and subsequently at the
Breasts. It has a reference, also, to the connection of the generative function
with the respiratory on the one hand, and the digestive on the other. (§. 715.)

* Annalcs du Museum d'IJist, Nat. t. xiii. p. 447.

309

true Copulation, but merely propagation without Sexes, by
means of Ova, or, at most, single Hermaphrodite Copula-
tion, (i. e. by different kinds of genital organs in one indi-
vidual.) In all the Bivalves, as has been shewn by Poli,
there is a large Ovary immediately below the Liver within
the Foot, in which the Ova are formed in such a manner,
that, {is I have frequently observed with the Microscope in
the Fresh- water Muscle, (Unio pictorum,) from 8 to 10
small Ova are contained in larger hulls or cases connected
together like grapes, # (Tab. II. fig. IX. f. fig. XII. C.)
in which they continue to grow for a certain time, and then
pass into the external laminae of the Gills, within the cells
of which, (§. 564.) as within a Uterus, they are converted
into perfect Bivalves. Hence, if we open a pregnant
Bivalve, we may take the young from out of the compart-
ments of the Gill to the number of some thousands, and
observe them moving briskly when placed on the slide of
the Microscope. The transference from the Ovaries to
the Gills (which last have even recently been considered
as Ovaries) is effected, according to OiCEN,f by means of
an opening direct from the Ovary on each side into the
canal placed above the compartments within each Gill.
This statement, however, appears to rest on the authority
of a single observation, and is, in my opinion, still doubtful,
because, in numerous examinations of pregnant and ur-
impregnated Bivalves I have never been able to discover
this opening ; whence, likewise, it seems to me more pro-
bable, that the Ova, as in the Medusae:}: or Actiniae, (§. 718.)

* This is remarkable, because, according to Cavolini, the Ova of several
Zoophytes are similarly massed together in the hulls by which they are
surrounded.

f GoeUing. gel. Anzcigen. 1806.

J In them there was a similar transference of the Ova from an internal to
an external organ. (See §. 717.)

310

enter the Stomach* by one of the openings hitherto con-
sidered as belonging exclusively to the biliary ducts, and
are then evacuated through the mouth, and conveyed into
the openings of the Gills by the water which flows through
the Cloak from before backwards; though it must be men-
tioned, that a prominence on the Rectum (Tab. II. fig.
IX. a. 6.) has much resemblance to an Oviduct. The
young animals must ultimately escape by two tubes (vaginae)
(fig. IX. t. t.) running above the compartments of the
Gills and opening below the anal tubes. The parts which
in these and other Bivalves have occasionally been con-
sidered as male organs, are of a very dubious nature.

§. 7 19. There are many varieties of this organization
in the different species of the Order, of which some are
but imperfectly known, and others unsuited for extended
description in this place. I shall, therefore, only notice
the very considerable deviation in the Ascidise : in them,
an Oviduct (i.) arises from the Ovary, (Tab. II. fig. II.
h. h.) which is here, also, placed below the Liver; it con-
veys the ova either through the anal opening, or through
the lateral aperture of the Gill-bag, (§. 562.) to the ex-
ternal surface of the fibrous case, where the young animals
remain fixed, and undergo a farther developement.f
Opposite to the opening of the Ovary, I remarked the
orifice of another glandular organ, (fig. II. k. 1.) which
apparently possesses the character of a male organ, or
serves to furnish the gelatinous covering of the Ova.

• The crystalline style, before mentioned, (§. 437. ) may probably in that
case have the same character in these animals as the peculiar dart of Snails.
(§• 722.)

f See the Essay before quoted from Meckel’s Arcihiv. b. ii. h. 4.

311

(b.) Gasteropoda.

§. 720. Instead of the formation of Ova without the
existence of Sexes, or the self-copulation of perfect Her-
maphrodites, as in the preceding Order, we here, for the
first time in the series of animals, find a distinction of
Sexes in different individuals, which is the case in those
species possessing Gills placed within the cavity of the
Cloak : nay, in the higher Species, i. e. in those breathing
by detached Gills or pulmonary cavities, we find as a repe-
tition of the inferior formations that each individual is
furnished with sexual organs of both kinds; in such a man-
ner, that self-copulation is no longer possible, and mutual
copulation necessary. We shall examine some species as
specimens of each of these organizations, selecting first the
Viviparous Snail (Cyclostoma viviparum) as an instance of
those Gasteropoda in which the Sexes are completely
separated. In the female, we find a whitish Ovary between
the respiratory cavity and the Liver, with an Oviduct pro-
ceeding from it behind the pecten of the Gills, (in the
same manner as the Vagina of the Fresh-water Muscle
over the laminae of the Gills,) (see Tab. III. ,fig. X. f.) :
it h^re, also, supplies the place of a Uterus, the Ova being
detained in it for a considerable time, and there developed
into young Snails (like the Bivalves within the Gills),
distending the canal in an extraordinary degree. In the
male, the Testis (fig. XI. a.) occupies the situation of
the Ovary in the female; a contorted seminal duct (z.)
proceeds from it to the Penis (y.), which can be protruded
through an opening in the right Feeler. In other Species
of this kind the Oviduct serves simply as such, and the
Ova are developed external to the body of the mother; as,

312

for instance, in the Buccimim undatum : it is remarkable,
however, that here, as well as in most Snails, several are
evacuated together in a covering common to all,f by which
we are reminded of the hulls for the Ova in the Ovary of
.Bivalves and of similar appearances in Zoophytes. The
male of this animal is, also, distinguished by an extraor-
dinarily large Penis, which can at pleasure be protruded at
the right side of the neck, or retracted within the pulmo-
nary cavity.

721. Among the Hermaphrodite Gasteropoda, where
the Copulation is mutual, we shall consider more particularly
the Helix pomatia. In each individual there is a moderately
large Ovary (Tab. III. fig. III. q.) situated below the upper
extremity of the Liver, with a convoluted seminal tube (r.)
descending from it, and which, after contracting a little,
suddenly expand into a capacious, mucous, plicated Vagina
(w.), in which the Ova receive an albuminous coating, and
are united into masses. At the orifice of this Vagina ter-
minate several secretory organs, the character of which is
as yet but imperfectly understood : of this nature are two
vesicles (x. x.) with numerous ramifications, and a bladder
with a long neck (v.). The male organs consist of a large
Testicle (t.), a seminal canal, at first attached along the
Vagina (t.# u.), and then taking its course to the Penis;
and lastly, the Penis itself (a.), moved by a muscle ( a
and provided with a long appendage (a/). Both Penis
and Vagina ultimately terminate in the common sexual
cavity, {fig. III. z. fig. IV. a.) opening externally below
the right large feeler, (fig. I. c.) and presenting in its
blind appendage (fig. IV. b. fig. III. y.) the little pointed
calcareous body or dart (fig. IV. *) attached to a small

t These hulls or cases in the Buccinum undatum form masses as large as
a fist, and each contain some dozens of dot-like Ova. (See Oken’s
Zooloyie, b. i. s. 211.)

313

projection. In tlie time of mutual copulation the sexual
cavity is protruded (like a feeler, §. 98. 110.) through the
external opening, the Penis at the same time is protruded
as far as up to the insertion of its seminal duct, (see the
sexual organs thus protruded, fig. XIII.) and the style or
dart comes into view ; which, after having served to produce
mutual excitement, is cast off and subsequently renewed.*
Nearly the same description will apply to the sexual organs
of Slugs (Limax); where, however, the ramified bladders
and the sac for the style (dart) are wanting. Lastly, the
sexual parts are similarly disposed in most others of the Gas-
teropoda breathing by detached gills or pulmonary cavities,
except that, according to Cuvier, these organs in some
species, e. g. the Aplysia and Onchidia, differ in the cir-
cumstance that the Penis is placed at a distance from the
common sexual aperture, and connected with it only by-
means of a groove. (See Tab. III. fig. VII.)

§. 722. Before quitting the consideration of the sexual
organs of the Gasteropoda, it still remains to notice some
secretory organs which appear to be closely connected with
the sexual function. In the first place it is remarkable how,
in the two first Orders of Mollusca, the respiratory organs
stand nearly in the same relation to the sexual organs and
rectum as the urinary organs in the superior animals ; a
circumstance which affords an additional proof of the cor-
Tectriess of the character before assigned to the urinary
system as a repetition of the respiratory organs. In addi-
tion, there are some peculiar excretory organs, consisting of
a tolerably considerable mucous gland, or rather mucous
cavity, which, placed in the vicinity of the respiratory
cavity, (Tab. III. fig. III. d.) usually empties itself close
to the anus by means of a peculiar excretory canal, (fig.

* According to Oken, ( Zoologic, b. i. s. 315.) the dart is to the sexual
aperture what the covering (§. 130.) is to the shell.

X. XI. 1.) taking- its course between the Rectum and
Vagina or Penis. In many marine Snails (Murex strom-
bus and others, and also the Aplysia), we meet with a glan-
dular organ beneath the margin of the cloak, which
secretes the purple fluid so celebrated amongst the ancients,
and is apparently related to the sexual function.

(c.J Cephalopoda.

§. 723. In this Order of Mollusca, the organization of
which is in so many respects more perfect than of those
that preceded, the sexes are always perfectly distinct,
though actual copulation does not appear to take place, the
fructification of the Ova being rather (as in dioecious plants)
the result of a simultaneous evacuation of ova and semen.
The female organs in the common Cuttle-Fish consist of a
large ovary, which is contained within a peculiar capsule at
the lower part of the peritoneal sac, (Tab. IV. fig. XV. d.)
and encloses a great number of ova, of various sizes, and
of an oblong pointed shape. (Fig. XVI.) The ova are
expelled by means of an oviduct (fig. XV. e.) placed on
the left side, so that they pass under the Infundibulum,
so often before mentioned, and are here evacuated with
the current of expired water, in the same manner as the
ova in Bivalves pass through the tube of the cloak. There
appear, also, to be other secretions intermixed with the
ova, giving to them the albuminous coating by means of
which they are united into clusters. As secretory organs of
this nature,* w'e may notice in particular two large flat oval

* These and similar glandular secretory organs in some degree supply the
deficiency of a Uteius in the inferior annuals, and, consequently, it is remark-

315

bodies, (fig. XV. g . g.) the internal structure of which
resembles the tubular substance of the human kidnies ; and
also a small reddish bladder, (f.) observed between them by
Swammerdam. The Sepia uctopodia and Cal mar sagittatus
differ from this structure in possessing a double oviduct, one
opening on each side.f

§. 724. In the male Cuttle-Fish, according to Cuvier,
a large, soft, and glandular Testicle occupies the situation
of the Ovary in the female : from it arises a seminal canal,
which first by its multiplied convolutions forms an epididy-
mis, and then opens into the upper extremity of a spacious
cavity, (described by Swammerdam as the Testicle itself,)
and containing, in addition to some thick mucus, numerous
little, elastic, vermiform tubes, the true nature of which is
altogether unknown, though they have been frequently
examined, and even mistaken for seminal animalcules. The
bag itself appears to be analogous to the glandular organs
in the female for the secretion of Albumen, and in this
view should be considered as a Prostate. (See note to
the last §.) The extremity of the seminal canal, projecting
beneath the Infundibulum, and placed above the peritoneal
sac, is situated close to the Rectum on the right side ; and,
though it does not actually serve as an organ for copulation,
has received from Cuvier the name of Penis. In two spe-
cimens of the Sepia octopodia, where I had the opportunity
of examining the sexual parts, (though not in a perfectly
fresh state,) I observed that a seminal duct proceeded on

able that in the superior animals, and even in Man himself, we find a rudiment
of the Uterus in the male in the form of a secretory organ, the Prostate.

The duplication of the sexual organs, wherever it exists, appears to be a
result of the union of two kinds of sexual organs (perfect hermaphroditism)
in a single individual in the lower Classes.

316

eacli side* from the Testicle, (Tab. IV. fig. II. z.) corres-
ponding to the two oviducts of this species : each seminal
duct had a glandular swelling (x.) at its origin, and opened
on the Peritoneum close to the Gills. Close to, and in
front of, the Testicle were two spacious sacs containing
thick mucus, and each opening above the seminal duct
by means of a peculiar excretory canal. (Fig. I. 1.)

Section III. Sexual Organs in the Articulata.

§. 725. It is remarkable that in this Class, where the
external form in general is more developed, the Sexes are
not only more uniformly distinct, and single copulation
the most common, but also that the sex impresses a pecu-
liar character on the entire form of the body, so that the
males and females are often very considerably distinguished
by differences in the size of the body, of their colours, or
even of the formation of the extremities: differences which
are pointed out by Natural History as regards Insects, but
which also occur in Worms; whilst in the Mollusca, on the
contrary, similar contrasts in the sexes of the same species
have not been observed, and probably do not exist. As re-
gards their sexual organs, however, many species of Worms

* As Cuvier has stated that the seminal duet is single in the S. octopodia,
I at first imagined that I was examining female organs ; but, on the one hand,
the nature of the testicle-like body, in which there were not any traces of
ova, and, on the other, the analogy between the male and female genital organs
prevailing through the whole animal kingdom, satisfied me that the view I
have taken is the most correct.

3i r

approximate by hermaphrodital formations to the preceding
Class, and many even to Zoophytes, by the probable occur-
rence of propagation without sexes.

(a.) Vermes.

§. 72 6. Among the Intestinal Worms, the Hydatids
(Entozoa cystica, R.) do not present any traces of sexual
parts,* and, consequently, appear to be produced by propa-
gation without sexes. In the Tcenise, (Cestoidea R.) small
fossae with external apertures, and situated in the middle of
all, except the anterior smaller, segments of the body, are
clearly recognizable as Ovaries, inasmuch as Rudolph!
observed not only Ova, but also young Tceniae in them.
There are also single canals and penis-like projections,
which appear to have the character of male organs ; whence
we may be allowed to suppose that these Worms are capa-
ble both of mutual hermaphrodital and individual herma-
phrodital impregnation.f The sexual parts of the Trematoda
appear to be hermaphrodital, whilst those of the Acantho-
cephala are distributed to separate individuals ; and in such
a manner that, in the Echinorhynchus for instance, almost
the yhole body appears, to be an Ovary filled with ova,
and emptying itself by a proboscis, whilst in the male, on
the contrary, the sexual organ consists in a bladder placed
at the farthest extremity of the body. Lastly, in the Nema-
toidea, the sexual organs are very distinctly formed. The
female is larger and thicker, and in much greater numbers

* Rudolpiii, Hist. Entozoor, t. i. p. 305.
f L. c. p. 317. The common Tape-Worm, at least according to Car-
lisle, is also capable of propagation by division.

318

tlian the male: the female sexual aperture is in the vicinity
ot the cephalic extremity, with a Vagina extending inwards
from it, and terminating in two very long (sometimes more
than six feet) and extremely contorted tubes, joined at their
other extremity, and containing an incalculable number of
minute Ovula. In the male there is a small thread-like
Penis (bifid, according to Rudolphi, in the Ascaris spicu-
ligera ), protruding at the caudal extremity, which dilates
internally into a thick canal (Vesicula Seminalis), two
inches long, which, in the last place, has inserted into it
a thread-like vessel (Testicle), two feet long, and convo-
luted around the Intestinal Canal. In the Cucullanus the
Penis is bifid (Tab. V. fig. VII. B.) ; the female sexual
orifice is more in the middle of the body; the Oviducts
more capacious than the Intestinal Canal, usually crowded
with living young ones, and occupying nearly the whole
of the body. (Fig. VII. A.)

§. 727. The sexual organs of the extraneous Worms
are in general but little known, though the hermaphrodital
formation (with mutual copulation, as in Snails) appears to
be the most common ; such is the case in the Leech, where
there are two sexual openings on the anterior half of the
abdominal surface,— an anterior male, and a posterior female.
(Tab. V. fig. IX. a. b.) The former leads to a conical
hollow organ, (fig. XI. a.) from the base of which proceeds
a thread-like vessel (probably the Penis). The base of this
cone is also perforated by the seminal ducts on each side,
(fig. XI. c.) proceeding from two large Epididymes, (fig.
XL b. fig. X. e.) the Vasa inferentia of which are given off
from a row of separate roundish pairs of Testicles. (Fig. X.
d.) The female orifice leads to a capacious \ agina, (fig.
X. g. fig. IX. e.) which is connected with the Ovaries
(g. g.) by two Oviducts. (Fig. XI. h.) In the Earthworm
there do not appear to be any true sexual apertures in the

319

situation where these animals adhere in the act of copula-
lation, i. e. in the region of the circular belt, (fig. I. b. c. d.)
but, instead, near the heart-like vascular circle, (§. 693.)
a row of Ovaries (fig. III. A. d. d. d.) around the (Eso-
phagus; whilst, on the contrary, I myself, as well as
Meckel* and MoNTEGRE,f have distinctly observed the
living young unattached between the cellular parietes
around the intestinal canal, corresponding closely to their
situation in the Cucullanus. The mode in which they
are removed from that situation is not very obvious, though
it is probably by means of the longitudinal projection at
the back of the intestine, which I find to be a hollow
tube.f (Fig- HI. k.) According to Cuvier, the Ova, or
young animals, are similarly situated in the Lumbricus
marinus and Aphrodite.

(b.) Crustacea.

§. 728. The sexes are here perfectly distinct, but the
sexual organs double, (forming, as it were, a repetition
of the two kinds of organs so commonly existing in the
preceding Order,) so that two male and female sexual
openings exist in each individual. In the female of the
CrajLFish there is a tolerably large Ovary upon the Intes-
tinal Canal behind the Liver, (Tab. VI. fig. XI. f.) from
which proceed two capacious Oviducts, (fig. XI. g. g.) sur-

• Translation of Cuvier’s Comp. Amt.

f Mtmoires du Museum d'Hist. Nat. t. i. p. 212.

t It is farther remarkable of the sexual bladders at the cephalic extremity
of the Earthworm, that, as already mentioned, (§. 572.) they agree, both in
form and situation, with respiratory bladders.

320

rounding' the Intestinal Canal and muscles of the tail, and
terminating at the root of the third leg on each side. (Fig.
VIII. a.) When the Ova are expelled they are lodged
upon the little fin-like laminae under the tail, (fig. XII.)
which is so far remarkable, as it forms another instance of
the transference of the Ovum from an internal to an exter-
nal organ, and as these laminae are themselves merely
repetitions of the branchial laminae of the Squillae. In
the male there is a tri-lobed Testicle occupying the situa-
tion of the Ovary in the female, (fig. X. a.) and from it
arise two long, minute, white seminal vessels, (b.) which
are very much convoluted, like the seminal vessels of the
Ascaris, gradually increasing in thickness ; they then sud-
denly become small again, and immediately expand into a
Penis half an inch long, and contained within the body, (fig.
I. h.) but probably, like the Penis of Snails, protruded at the
time of copulation from a tubercle at' the root of the last
pairs of legs. Close to this tubercle, on the under surface
of the tail are two bony, groove-shaped, moveable masses,
which are considered by Cuvier as the true Penis, although
Cavolini* and others had already described them as being
merely excitative organs, because they are so far removed
from the opening of the seminal canal that it is impossible
they should be intended to conduct the semen to the ori-
fice of the Oviducts.

(c.) Insecta.

§. 729. In this extensive Order the sexes are invariably
perfectly distinct, and frequently the males and females so

* On the Generation of Fishes and Crabs, translated by Zimmermann.
Berlin, 1792, p. 121. He found two pairs of such parts in the Punger.

321

Very different as to appear as though they belonged to dif-
ferent species : individuals without sex are, however, very
common among Bees, Wasps, Ants, though more properly
to be considered as females in which the sexual parts are
undeveloped.* But though the internal sexual organs are
still ordinarily double, the external sexual openings are
single, as in the superior Animals. In the latter respect,
indeed, Spiders form a remarkable exception, reminding
us of the structure in Cray-Fish : in both sexesf the exter-
nal genitals are situated on the anterior part of the abdo-
minal surface between the bran c him, presenting in the
females two orifices (Tab. VII. fig. VIII. B. a. a.) belong-
ing to the very simply organized pouch-shaped Ovaries,
(d. d.) and in the male two openings (fig. VIII. B. a.)
belonging to the seminal canals (b.) of the similarly pouch-
like testicle, (c.) An evident approximation to the preceding
Order consists in the fact, that in the Onisci the Ova pass from
the Ovaries between some valves placed oil the abdominal
surface, in order to be there farther developed;^ which
valves have a great resemblance to those covering the Gills,
(§. STT.) and are also situated in the immediate vicinity
of the respiratory organs. It is remarkable that this deve-
lopement of the Ova in an external organ is so far imitated
even in Spiders, that the female surrounds the Ova as they
escape with a web ; the bag thus formed being attached to
its own body by the Aranea saccata , and carried about

* The influence of the difference of sex on the developement of theextre.
mities is very remarkable ; for, in the Glow-Worm, for instance, the female,
and in Ants those that are without sex, are Apterous.

f Previous to Treviranus it was supposed that the male organs of
Spiders consisted in the Antennae : he has shewn, however, that their knob-
like extremities are merely excitative organs. ( Ueber . d. Bau d. Arachnid.
s. 37.)

t G. R. Trkviravus on the Organization of Apterous Insects, in his Vor-
niixchte Schriften. 1>. i. s. GO.

VOL. If.

322

with it. In the Scorpion, Treviranus* found the exter-
nal genitals alike in both sexes, (the male being distin-
guished only by two small penis-like projections,) and
consisting of a small opening with a comb-shaped lamina
on each side. The internal organs consist, in the female,
of three tubes connected by transverse vessels, (in the
oviducts of the Scorpion, Redi usually found from 26 to
40 young ones,) and in the male, of two testis-like bodies,
with vasa inferentia arising from the Liver or adipose body.f

* Ueber d. Ban. d. Arachniden, s. ] 1.

* In Woodlice the male organs consist of a Penis placed at the extremity-
of the abdomen a little above the anus, and communicating with a common
spermatic duct arising by two vasa deferentia from the Testicles, which
are elongated and formed by a single order of vessels. The female organs
consist of a vulva leading to a common Oviduct, which divides into two,
and sometimes four, branches or ovaries. These animals are viviparous,
the young ones being hatched within the uterus or common oviduct, and
when hatched escaping at the lower part of the abdomen in order to be
lodged between the legs of the mother until they are capable of independent
existence.

In the 'Phalangides the male organs are composed of two white pyramidal
testicles, with two vasa deferentia proceeding from them, and opening into a
large common seminal canal, within which is a cylindrical horny projection
that probably serves as a Penis. The vesiculse seminales also open into a
common seminal canal, and are formed by two cylindrical, capillary, and ex-
tremely contorted tubes. In the female there is a common oviduct opening
by one extremity at the upper part of the body near the mouth, and at the
other communicating with two canals, which dilate into the Ovaries. The
most remarkable circumstance, however, is the canal by which the Ovaries
again dpen near the mouth. It is six times as long as the body, and after
gradually contracting for a certain space, suddenly expands into a cylindrical
tube. It consists of two membranes ; of which one is cellular, and surrounds
it loosely, whilst the other is composed of spirally convoluted fibres, and is
very elastic. The Ova, which are formed in one only of the Ovaries at a
time, are found in the part of this canal next the Ovary, the common ovi-
duct first described probably serving rather as a Vagina than as an oviduct
properly so called. — (Marcel de Serres, Menu du Museum, v. 83, 108.)
— Translator.

323

§. 730. The organization of the sexual Organs in the
more perfect Worms without vessels, e. g. the Ascarides,
may serve as a prototype for those of the remaining Insects
which breathe through Tracheae. As in them, so also here
the seminal organs as well as the ovaries are merely long,
and frequently very much convoluted, tubes; so that there
are in fact neither Ovaries nor Testicles properly so called,
but merely seminal canals and oviducts ; which, however,
are usually connected with several secretory organs of
various kinds. In the Gryllus verrucivorus , among the
Orthoptera, we find two large tuft-shaped Ovaries, which
consist of numerous tubes placed near each other, and inter-
woven with extraordinarily large and numerous Tracheae.*
Both empty themselves by a common Oviduct, which
unites with that of the opposite side into a short Vagina,
into which opens a little bladder, provided with a peculiar
convoluted secretory vessel terminated by a blind extre-
mity. From the Vagina the Ova pass into a laying tube of
considerable length, which exists also in several other In-
sects, e. g. Wasps, (reminding us of the evacuation of the
Ova through the tube, of the Cloak in Mollusca, §. 718.
723.) and here consists of two long, narrow, and pointed
laminae closing into each other at the sides. The male
organs consist in two yellowish Testicles, (Tab. VII. fig.
XXIV. a.) formed by seminal vessels, and penetrated by
numerous Tracheae: the excretory duct by its minute con-
volutions forms an Epididymis, (fig. XXIV. b.) then re-
ceives two tuft-like bundles of coecal vessels, (h. i.) and,
lastly, opens together with that of the opposite side into
the Penis, which presents a tongue-like body, (e.) sur-
rounded by a circle of skin armed with two little hooks.

• Is it not probable that the number of these Tracheae is connected with the
very considerable size to which the Ova of these animals attain within the
body of the mother ?

Y 2

324

Among- the Hemiptera, the female organs of the Water
Scorpion (Nepa), according to Swammerdam, consist of two
Ovaries formed of five canals, the Ova being distinguished by
a row of bristles at their upper extremity : the male organs
are formed by two bladders with two extremely convoluted
seminal tubes, and on each of them five seminal vesicles,
at the base of each of which is inserted a minute testicle-like
convoluted seminal vessel. Among the Neuroptera, I shall
notice only in the Libellula the remarkable position of the
male organ at the anterior part of the long and narrow
abdominal surface, whilst in the female it is at the poste-
rior part of the body, thereby explaining their peculiar
mode of copulation.*

§. 731. Among the Hymenoptera, Swammerdam
found in the Queen Bee two large Ovaries consisting of
numerous strings of Ova, estimated to amount to ten or
twelve thousand : the Vagina is placed at the termination
of the common duct of the two Ovaries, and has connected
to it a little bladder with two secretory vessels, which here,
as well as in other "Insects, are supposed to prepare the
viscid covering of the Ova. The male organs of Bees con-
sist of two Testicles of tubular structure, two seminal ducts,
two bladders, and a Penis, which, like that of Snails, is
everted when it is protruded. In the Coleoptera, the female
organs are simpler, and more like those of the Water
Scorpion : in the Rhinoceros Beetle, for instance, accord-
ing to Swammerdam*'! there are only six tubes on each
side, containing but a moderate number of ova ; and the
Vagina again receives several secretory organs. In the
male the two Testicles are divided into six little flat bodies,
each sending off a little canal, which, uniting with the
rest, assist in forming the common seminal canals, that
enlarge as they proceed downwards on each side. Where
* Swammerdam, Bibl. Nat. p. 9G. f L. c. Tab. XXX. fig. X.

293

the two seminal ducts unite in the canal of the Penis,
there are also two little seminal bladders, into the bottom of
which opens a delicate convoluted vessel, about 20 inches
long. In the Lepidoptera we may take as an instance the
sexual parts of the Papilio brassiccs , L. lately so well de-
scribed by Herold.* The female organs consist on each
side of four long spirally convoluted tubes, containing a
great number of Ova (Tab. VII. fig. XXVI. A. a. a.) ;
both organs unite in a short Vagina, that also receives
the orifices of a simple bladder and of a smaller one with
two cornua and secretory vessels, (c. d. e.) as well as a
larger cavity, (b.) which Herold considers as the recep-
tacle of the male semen. The male organs are a red
spherical Testicle, composed of two halves (fig. XXVII. A.
a.); two long and delicate [seminal canals, (b. b.) each of
which receives a long convoluted seminal vessel (c.) before
it unites with its fellow to form the common seminal duct,
(d.) It is remarkable in the history of the developement
of these organs, that in the very young Caterpillars the
organs of each kind differ but little, and appear as little
buds (fig. XXVI. C. female, fig. XXVII.] D. male) ; in
the full-grown Caterpillar approach more closely to their
subsequent form, (fig. XXVI. B. fig. XXVII. C.) and
attain their ultimate perfection in the Pupa.

/• Entwicklungsgcschickte des SchmettcrUngs. Cassel und Marburg. 1815.

326

B. Sexual Organs in Animals with Spinal Marrow

and Brain.

Section. I. Fishes.

§. 732. In the species of animals reviewed in the pre-
ceding' paragraphs we found it a general rule, with a few
exceptions, ( e . g. the Cephalopoda,) that the ova are formed
in considerable numbers in the organs destined for that
purpose, and then simultaneously evacuated to be again
simultaneously renewed, (like the yearly production of new
fruits on Plants;) if, indeed, the animal be capable of
repeated generation, which is not the case in ' most Insects
for instance. In the higher Classes of Animals, on the con-
trary, it generally happens that the Ova, when they can be
detected preformed in the Ovaries, are originally formed in
a definite number, but then gradually arrive at maturity,
and detach themselves, so that there are constantly Ova in
the Ovaries, but of very different sizes. Most Fishes,
however, here again form an exception, and approximate
to the inferior Classes by the periodical and simultaneous
growth, evacuation, and regeneration of large numbers of
Ova: nay, there are even some species in which various
observations have rendered it probable that the hermaphro-
dital formation exists, by means of which they are rendered
capable of self-impregnation. This is the case, according
to Cavolini,* in the Perea marina and the Canna (Hia-
tula Salviani, L.); and, according to HoME,f in the Lam-

* Uebcr Erzengung d. Fische und Krebse, s. 82.
f PMosoph. Trans. 1815.

327

prey (Petromyzon marinas ) as possessing both Testes and
Ovaria. I confess, however, that though I find the Ovaries
very distinctly in the Lampreys, I am still doubtful as to
the true character of the Testicle-like body, inasmuch as it
is very possible that these animals, which have so much
resemblance to Worms, may also approximate to them in
the circumstance that the females are found in much greater
number than the males.*

§. 733. The following is the usual state of the sexual
organs in the Osseous Fishes: — The Ovaries form two
large sacs extending on each side of the Intestinal Canal
to the under surface of the Liver, and attached by a kind
of Mesentery : they are supplied and fixed by minute
blood-vessels, and have processes extending from the inner
surface of their parietes, to which the Ova are attached,
and in such numbers, that towards spawning time the Ova-
ries occupy nearly the whole of the cavity of the abdomen,
some hundreds of thousands of Ova having been counted
in a single Fish. These sacs open by two very short ex-
cretory canals, which immediately unite into one, termi-
nating together with the urinary organs immediately behind
the anus. (Tab. X. fig. III. A. B.) The Testicles (Tab.
IX. fig.. XVIII. XIX. h.) present precisely similar sacs,
containing, instead of Ova, a whitish, seminal (and, accord-
ing to Fourcroy and Vauquelin, highly phosphorescent)
flujid, secreted from their internal parietes, and discharged
at the same place as the Ova of the female. Like the
Ovaries, also, the Testicles swell at the spawning season,
and it is easy to see from this organization, what is also
proved by observation, that no copulation, properly so
called, can take place. As deviating from this form, I
may notice, first, the Ovaries of the Trout, of moderate

* Among the Ascarides, for instance, the number of males is very
inconsiderable.

328

size and situated high up close to the Liver; in which I
do not find the Ova simultaneously developed as in the
Carp, Pike, &c. but, on the contrary, of various sizes: nor
is there any peculiar Oviduct to be detected, the Ova,
which when they have attained their full growth are nearly
as large as a pea, detaching themselves and falling into the
cavity of the abdomen, which therefore is frequently found
quite full of unattached Ova. They are evacuated, how-
ever, through the openings, before mentioned (§. 472. 599.),
of the abdominal cavity close to the anus, which openings
these Fishes, even the Males, possess as well as the Rays,
with this difference only, that they here unite into a com-
mon external aperture. This circumstance, not before de-
tected by any observer, is remarkable, in so far as it reminds
us of the deposition of the Ova within the abdomen of
several Worms, and serves to throw a clearer light on the
true nature of these mysterious openings into the abdomen;
inasmuch as they here serve as uterine apertures, of which
they are merely a repetition in the higher Order of Rays
and Sharks, and in them stand in relation to the respiratory,
connected as it always is, with the sexual function.

§. 734. A remarkable transition to the Cartilaginous
Fishes is formed by several Osseous, e. g. the Blennius
viviparus, which bears living young, though we still need a
more complete investigation of its sexual organs. As re-
gards the Cartilaginous Fishes, their sexual organs in the
Branchiostegi, e. g. the Sturgeon, agree with the usual
form of those of the Osseous Fishes; but there are also
viviparous species, e. g. the Syngnathus acus , of which
Aristotle long ago remarked, that the young escaped
through an extensive .fissure in the abdomen, which again
closes after their birth ; a fact confirmed also by Cavoljni,
who states, that the young are formed in a sac behind the
anus, which opens when they arrive at maturity: a remark-

329

able phenomenon, which, however, appears to me to agree
closely with the mode of expulsion of the Ova of the Trout,
and may probably be explained by supposing that the Ova,
escaping from the Ovary, are developed in a particular
part of the abdominal cavity, and are then expelled through
a similar natural (not new-formed) aperture of the abdo-
men itself, which merely dilates in an extraordinary manner
at the period of parturition. Lastly, in the females of
Sharks and Rays, there are two small Ovaries situated
under the Liver, in which the Ova are developed indi-
vidually, not simultaneously, as in Osseous Fishes, and two
Oviducts, each of which (Tab. X. fig. IX.) receives the
Ova from the Ovary by means of a floating* extremity
placed near the Heart and Liver, for the most part con-
taining the young until the period of their full develope-
ment like a Uterus, and ultimately evacuating them through
the pudendum, which is situated behind the anus, and fur-
nished with a penis-like projection (Clitoris). In the
Squalus acanthias , Home+ always found several Ova sur-
rounded by transparent jelly, and enclosed within a common
capsule pointed at the corners (fig. IX. e.); he observed,
too, that the young were always completely developed
within these eggs, whilst, on the contrary, the Squalus
canicula is, according to him, merely oviparous. In the
male, the testicles are already of a more glandular struc-
ture, and occupy the same situation as the Ovaries in the

* This floating orifice (Fimbriated extremity of the Fallopian Tube in
Man) serves to distinguish the Oviducts of the superior from those of the
inferior animals, where the Oviduct appears to be merely a continuation of
the membrane of the Ovary. Is it not allowable to consider these orifices
as the apertures into the cavity of the abdomen (e. g. of the Trout) in-
verted and elongated into tubes?

f On the Mode of Breeding of the Ovi-viviparous Shark in the Philos.

Transact. 1810.

330

female (Tab. X. fig. II. n.) : the excretory duct by its
numerous convolutions forms a long Epidydimis, and then
dilates into a kind of Vesicula Seminalis, (p.) which is
connected with its fellow, and opens in common with the
urinary passages into a heart-shaped cavity with an ex-
ternal projection (Penis). Consequently, there is true
copulation, at which time the male grasps the female by
the posterior extremities, already noticed (§. 168). In the
Lamprey there is a similar conical projection, within which
the Ova and Semen are intermixed : two apertures lead to
it from the cavity of the abdomen, in which the Ova de-
tached from the Ovary remain until they are transferred
into this conical cavity, and thence ultimately expelled.

Section IL Sexual Organs in Amphibia.

§. 735. The Sexual Organs in this Class approach most
closely to those of Hays and Sharks. In the Frog, the
Ovaries are situated in the lumbar region: each is divided
into several (sometimes nine) lobes, and consists of thin
membranes, in and qpon which the Ova are formed, and
in such a manner, that, nearly as in Osseous Fishes, an
extraordinary number are produced at the spawning season,
distending the Ovary until they are deposited. At the
upper part of the Ovaries there are also peculiar oblong,
finger-shaped, lobes of fat supplied by their own vessels,
and which have been occasionally viewed as Renal Cap-
sules, but which, however, particularly as they are already
very large in the Larva, appear to me to serve rather as

deposits of nutritive matter subservient to the sexual func- .
tion, nearly like the fatty bodies in Caterpillars. The
Tubes or Oviducts open on each side between the Heart
and Liver,* then descend with many convolutions close
upon the vertebral column, each dilating, before its entrance
into the Cloaca, into a membranous bladder, in which the
Ova are collected, distending the body of the animal in an
extraordinary degree, and are then expelled in the form of
masses glued together by jelly ; thus reminding us of the
clusters of Ova in the Mollusca. As to this gelatinous
covering of the ova, it is secreted in the Oviducts towards
winter time, and, according to Branded is intermediate in
composition between mucus and albumen, on which account
it swells extraordinarily in water, as I have often had occa-
sion to observe.:}: In addition to these internal organs,

there are, also, in the Surinam Toad external organs sub-
servient to the formation of the young, and perfectly re-
sembling phenomena before noticed, e. g. in Bivalves,
&c. The ova are here impregnated by the male on the
back of the female, and it is not until that time that the
cells on the Surface of the back are produced, in which the
animal hatches its young; a circumstance that receives

* From the remoteness of the termination of the Oviduct from the Ovary,
the transference of the Ova from the one to the other is very difficult of ex-
planation, and can only be imagined to take place by the existence of a direct
attraction between them.

f See Home’s Essay on the Breeding of the Shark. Philos. Trans. 1810.
p. 205, where this jelly is stated to be similar to that found in the Oviduct
of the Shark.

f In spring it is common to find near brooks, or after rain, masses of
tough mucus with fragments of these Oviducts, which have been ejected by
Birds on account of the manner in which they have swollen. They were
formerly considered as the jelly of star-shoots, or as a Tremella (nustoc) ;
but I have evidently distisguished fragments of the Tubes in such masses.

332

additional interest from the fact, that it is the cutaneous
organ, which, as we have already seen, is the primary
respiratory organ that is employed in supporting the young.
In the male Frog, there are two oval Testicles of granular
substance, provided with two little fatty lobes like those of
the Ovaries, and like them increasing very considerably at
the breeding season; and also two seminal canals connected
with the Ureters, and dilating into Vesiculae Seminales
previous to their entrance into the Cloaca. Here, also,
there is not any proper copulation ; instead of which, the
male grasps the female by means of two thumb-like tuber-
cles, which appear at the spawning season, and pours his
semen over the Ova as they issue from her. The female
sexual parts of Salamanders are distinguished from those of
Frogs as regards the Ovaries, (Tab. XIII. fig. IV. g.) in
which the Ova are more permanent, and detached in smaller
numbers at once. The Oviducts (d.), also, are each
dilated inferiorly, not into a bladder, but into a long canal,
within which the Ova are developed precisely as in a double
Uterus. The male organs consist of a double Testicle on
each side, (Tab. XIII. fig. III. h.) several blackish tube-
shaped Vesiculae Seminales turned towards the Kidnies (k.),
and two small triangular folds of the Cloaca, which appear
to be rudiments of a double Penis (e. e.). In the Proteus,
too, where rudiments only of Ovaries had been admitted,
Rudolphi* has discovered not only Ovaries and Oviducts,
but also in other individuals Testicles and Seminal ducts.f

* Oken’s Isis, b. i. h. vii. s. 1017.

f That the Aloxotl, or Mexican Proteus, is also a perfect animal, and not
merely a Larva, has recently been established by Sir E. Home, who found
in different specimens both male and female organs, not differing in any
essential points from those of the Batrachiu. (Philosojih. Trans. 182L p.
ii. 429. ) — Translator.

333

§. 736. In the Mud-Tortoise (T. lutaria ) I find two-
large Ovaries at the ower part of the abdomen, to which
are attached, by means of pedicles, bright yellow Ova
covered by a very vascular membrane which remains as a
Calyx, after the expulsion of the Ova, and then withers
away. The Oviducts are very long, attached to a vascular
Mesentery, and in the individual that I examined contained
on the right side six, and on the left three eggs an inch
long, and with solid shells. Both Oviducts opened into the
Cloaca, with which two empty membranous bladders were
connected on the right and left sides : there was, also, an
egg in the Cloaca, and a Penis, small, but otherwise pre-
cisely like that of Man. In the male, I find two oval
yellowish-red Testicles below the Kidnies, with a kind of
Epidydimis formed by their large and blackish seminal
ducts, which last open at the root of a large and tongue-
shaped Penis, concealed within the Cloaca, moved by its
peculiar muscles, and grooved at its extremity, instead of
being perforated like that of Man.*

§. 737. In Serpents, the Ovaries, forming two elongated
bodies furnished with Ova of different sizes, are situated
on each side of the Spine above the Kidnies : the Oviducts
are of considerable length, and the Ova within them ar-
ranged in such a manner, that those lodged within one
correspond to an unoccupied space in the other. In the
Viper, too, as in the Salamander, the Oviduct serves for
hatching the ova. These canals open into the Cloaca
close to the Ureters. In the male there is an oblong
Testicle on each side with a very much convoluted seminal
duct, that with its fellow opens into the Cloaca at the root

* Hence in these animals there i9 an ardent and long-continued
copulation.

334.

ot a double,* grooved Penis; which, though not capable of
being very far protruded, permits of actual copulation.
Nearly similar, too, is the disposition of the sexual organs
in Lizards, except that the course of the seminal duct
being shorter, it forms a more perfect Epidydimis, and that
in the Crocodile the Penis is single.

Section III. Sexual Organs in Birds.

§. 738. The female sexual organs of Birds are extremely
similar to those of Amphibia, particularly Tortoises, except
that here, and here only of the higher Classes of Animals,
the internal genital organs are single. The Ovary is placed
in front of the Aorta, above the Kidnies, and below the
Liver (Tab. XV. fig. XII. f. Tab. XVI. fig. XVI. a.);
has a clustered shape; and increases considerably in size at
certain periods in those Birds that breed periodically : it
contains some hundreds of soft Ova of different sizes, sur-
rounded by a vascular membrane, which forms pedicles for
their attachment, and as they increase presents a white line
in front, (Tab. XVI. fig. XVI. c.) indicating the spot at
which the vascular membrane (Calyx) gives way in order
to allow the escape of the Ovum, subsequently shrinking
away, (d.) The egg is received into the single oviduct,

* This double Penis corresponds to the cloven Tongue of these Animals t
to the double Penis of several Worms, and to the double sexual organs of
many of the inferior animals.

335

which commences by a line membranous and funnel-like
orifice, and gradually assumes nearly the form and struc-
ture of a common Intestine,* except that it is softer and
more flattened : it is attached by a mesentery, and making
several convolutions (fig. XVI. f.) descends to the Cloaca.
The internal membrane of the oviduct varies in different
points: it is first precisely like the villous membrane of the
Intestine; is then plicated; presents long villi at the point
where the egg remains for a considerable time, and where
its calcareous shell is secreted ; and then again becomes
smoother, and plicated longitudinally : this, however, does
not form any ground for dividing it into Vagina, Uterus,
and Fallopian Tubes, inasmuch as the Ovum is here deve-
loped external to the body of the mother, and the whole
Oviduct, consequently, is analogous to the Fallopian Tubes
in Man. The Oviduct always enters the Cloaca on the left
side near the Rectum, (*fig. X. b.) where it is furnished with
a sphincter muscle : according to Perrault, also, the
Ostrich and Cassowary present traces of the existence of a
little Penis, shaped like that of Man. Lastly, the various
stages of developement are very distinctly perceptible in
these genital organs, the Ovary and Oviduct being reduced
in old Birds nearly to the same inconsiderable size as they
originally present in young ones.

§.739. The male genital organs of Birds approximate
still 1 more closely than the female to those of Amphibia,
owing to the existence of two Testiclesf and their semi-,
nal ducts. I he Testicles are situated at the upper end of
the Kidnies on each side of the Aorta, their size being
subject to much variation according to the season of year;

• There is even the same peristaltic motion of their contents in both
cases.

t As an occasional variety there is sometimes one, and more rarely there
are three Testicles.

33 (>

so that at breeding time they are of extraordinary size,
and at other periods frequently scarcely perceptible. (Tab.
XVI. fig. XV. a.) The left is generally larger than the
right, as has also been remarked by Tannenberg and
TiEDEMANN:f their shape is usually oval, their colour yel-
lowish ; and their very soft and delicate parenchyma,
inclosed within a thin and vascular membrane, frequently
gives to the whole Testicle a striking and, physiologically,
very remarkable resemblance to one of the Ova in the
Ovary, consisting merely of yolk. Several canals issuing
from each Testicle unite to form the very much convoluted
seminal duct, composing the Epidydimis, (fig. XV. b.)
which is particularly distinct at the pairing season, and
which often presents a peculiar imperforate seminal vessel
ascending towards the Renal Capsules, or cavity of the
Thorax. The seminal duct, descending towards the Cloaca,
is arranged in close serpentine convolutions; is firmly
attached to the Ureter (fig. XV. c.) ; immediately before
its termination at the edge of the Rectum, close to the
Ureter of the same side, presents a small vesicular dilata-
tion; and, as is also the case in several Amphibia and
Fishes, a small gland that may be compared to the human
Prostate. Each seminal duct terminates on a wart-shaped
projection, which together correspond to the double Penis
of Lizards; but there is also occasionally a larger Penis,
essentially similar to that of’ Tortoises, e. g. according to
Tiedemann, in the Ostrich, Cassowary, Bustard, and
Stork, and likewise in Ducks and Geese. It consists of
tongue-shaped body, grooved superiorly for conducting the
semen, and moved by peculiar muscles : in Ducks it is of
very considerable length, amounting to some inches, being
protruded at the time of copulation like the Penis of Snails

f Zoolot/ie, b. ii. s. 697 ; and G. G. Tannenberg, Spicilegium Obscrva-
tionum circa partes Gent tales Masculas Avium. Gott. 1789.

337

or the long tongue of Serpents, and at other times being
concealed within a peculiar sac of the Cloaca. We must
not quit the genital organs of Birds without noticing the
remarkable differences in the size and plumage of this Class
connected with them, inasmuch as this circumstance, as well
as the developement of the Ova external to the body,
indicate an approximation to the type of the more perfect
Insects.

Section IV. Sexual Organs in Mammalia.

(a.) Female.

§. 740. In the female procreative organs.of the preceding
Classes we have observed, ls£, the Ovaries, invariably ex-
isting ; 2d, in some species only, e. g. Bivalves, Crabs, and
even among Amphibia, in the Pipa, external organs sub-
servient to the support of the young, not immediately con-
nected with the internal genital organs, and often originally
devoted to other functions ; 3 d, internal organs which
permit the birth of the young either in a state of complete
developement, or still included within an egg, — as is the
case in some Insects, e. g. the Scorpion, — in Snails, — in
most Fishes, — in Salamanders and Vipers. It is only in
Mammalia that all these organs are combined, and conse-
quently in them we find, ls£, as generative organs, — the
Ovaries ; 2d, as internal organs for conveying and perfect-
ing the Ovum, — the Oviducts, (Fallopian Tubes,) Uterus,
and Vagina, together with the external copulative organs

VOL. IK z

338

situated at the orifice of the latter ; 3d, as external nutri-
tive organs, — the Mamma, the existence of which, we shall
find, is connected with the composition of the Ovum in
Mammalia, in which the yolk of the Ovum in Birds (form-
ing, as it were, a receptacle of Chyle for the nutrition of
the young after the period of incubation) is for the most
part wanting, thereby rendering necessary the existence
of another organ for the nutrition of the young after birth.
These latter organs are the only ones which have hitherto
been looked for in vain in only two species, viz. the
Ornithorhynchus and Echidna. We shall proceed succes-
sively through the different forms of these organs, assuming
the human organization as the general prototype, and
considering more particularly the different deviations
from it.

§.741. 1. Ovaries. There are invariably two, even in

the Ornithorhynchi and Echidna; but in several species
they approximate considerably to the form of these organs
in Birds and Amphibia, in so far as it is very easy to detect
their composition of individual ovular vesicles. This is
particularly the case in the Rodentia, e. g. in the Rabbit,
Rats, Guinea-Pig, Hedgehog, and, according to Cuvier,
above all in the Opossum. So, also, the Ovaries of Swine
are composed of several globular masses of various sizes ;
which, however, are not so much individual Ova as separate
small Ovaries, because when cut into they present a dense
texture with little cells exactly like a human Ovary, and
are also found in the same state during pregnancy. (Tab.
XX. fig. IX.) Lastly, I may mention the singular elon-
gated form they present in the Porpoise, as observed by
Hunter, * resembling the figure of the Pancreas, and cor-
responding to their shape in the human embryo.

2. The Fallopian Tubes (Oviducts) continue to present
* Philo soph. Trans. 1787, p. 444. (Their length five inches.)

339

their expanded orifices to the Ovaries, as was the case in
Amphibia and Birds: inferiorly, however, they open into
the Uterus instead of the Cloaca, and differ from those of
Women principally in their smaller size in proportion to
the Uterus, in their more contorted course, and in the less
indented margin of their abdominal orifice, (Tab. XX. fig.

IX. b.) which is occasionally very large, e. g. according to
Hunter, five or six inches across in the Porpoise.

§. 74-2. 3. The Uterus. When in the preceding Classes

of Animals we found internal organs for containing the
young during the period of their developement, and the
living young ones born either as such or enclosed within
an egg, those organs consisted merely in dilated portions of
the Oviducts, forming as it were two Uteri, each of which
emptied itself by its own aperture through the common
sexual opening. Among Mammalia this, according to
Home,* is the case in the Ornithorhynchus; in which
each Oviduct is somewhat dilated inferiorly, thus forming
a kind of Uterus, opening opposite to its fellow into the
short Vagina in such a manner that the orifice of the Blad-
der is intermediate between the two openings of the Uteri,
neither of which is surrounded by a Cervix. (Tab. XX. fig.

X. ) The nearest approach to this form is in the perfectly
double Uterus of most of the Rodentia, e. g . Hares, Rab-
bits, Rats, and Mice, which opens with two separate pro-
jecting orifices into the Vagina, each half like the Oviducts
of Birds and Amphibia, completely resembling an Intestine,
even in the arrangement of its muscular fibres: of the same
kind are, also, the Uteri of Swine, formed almost pre-
cisely in the same manner. Next come the different kinds
of Uterus single in the middle, but with lateral Cornua.
It is necessary first, however, to notice the remarkable

* Phil. Trans. 1802, p. 81.

Z 2

340

structure of this organ (Uterus aufractuosus) in the marsi*-
pial animals, — Opossums, Kanguroos, Wombat, &c.

§. 743. In them, as in the animals with a perfectly
double Uterus, there are two openings into the Vagina,
with the orifice of the urinary bladder between them :
each of these uterine orifices leads to a separate canal
bending considerably inwards, and resembling an ordinary
intestine-like Uterus, the upper extremity of which unites
with that of the opposite side to form a capacious cavity
terminating in a point inferiorly. (Tab. XX. fig. XIII.)
This central cavity is incompletely divided into two lateral
halves by a longitudinal ridge, and appears to be com-
pletely closed at its lower part when unimpregnated. Ac-
cording to Home,! however, during pregnancy, and also
during parturition, and for some time subsequently, it
opens into the Vagina by a narrow fissure, through which
the young passes in the state of a perfect embryo, (occa-
sionally weighing 21 grains, when the mother weighs 56
pounds,) by means of the Vagina, into the bag containing
the mammae : the semen, on the contrary, probably passes
through the lateral canals in its course to the central cavity,
which receives the Ova from the Ovaries by means of two
Oviducts, that become larger as they descend. A gelati-
nous substance, like that found in the Frog or Shark, is
secreted within this Uterus during pregnancy in such quan-
tity that the lateral canals are completely obstructed by
it, and the young animals firmly incased within it. A
similar jelly is found likewise in the pregnant Uterus of
most Mammalia, where it serves, however, merely to close
the orifice of the Uterus, e. g. in the Cow, Horse, Hog, & c.

§. 744. There is this peculiarity in the Uterus of the
Carnivora, certain Rodentia, c. g. the Agouti and Guinea-

f Philos. Trans. 1795.

341

Pig, Bats, Cetacea, Ruminants, Swine, and Solipeda, that
though opening interiorly by a single orifice, it is elongated
superiorly into a Cornu on each side, (Uterus bicornis,)
which is usually longer and more intestine-like in propor-
tion as it serves to lodge a greater number of Ova. Such
is the case, for instance, in the straight-horned Uterus of
the Dog and Cat Genera, of the Bat and Seal, as well as
in the Uterus of the Pig, Hedgehog, and Mole, with
Cornua bending downwards: a long-horned Uterus of this
kind, which comes nearest to a double Uterus, might be
properly called Uterus bipartitus; and that with short
Cornua, on the contrary, distinguished more peculiarly as
Uterus bicornis. In those animals, e. g. Ruminants and
Solipeda, where there is usually but one young one at a
time, the Cornua of the Uterus are shorter, forming as it
were merely appendages to the central part, with this
difference, however, that in the Ruminants, e. g. the Sheep
and Cow, (Tab. XX. fig. XVI.) there is an imperfect
septum in the body of the Uterus (bicornis divisus), which
is wanting in the Solipeda (Uterus bicornis simplex). The
mode of attachment of the long-horned and double Uterus
of Mammalia is also remarkable, not consisting merely, like
that of the Oviducts of the inferior animals, in a kind of
Mesentery, of which the broad ligaments- of the simple
Uterus are rudiments ; in addition to these there are also
rotind and vascular fibrous cords, which exist as round liga-
ments passing through the abdominal rings even in the
more simple form of Uterus, e. g. the human, but are here
double, extending in the same manner downwards from the
region of the crura of the Diaphragm resting on the spine,
:is from the abdominal ring upwards.*

* These supciior round ligaments of the Uterus have been particularly
noticed by Rujjoli’iu and Nrrzscii. (Meckel’s Archiv. b. ii. h. 2.) The
fruc cliai acter of the round ligaments is very obscure, but they appear to

312

§. 745. The last principal form of the Uterus is trian-
gular or oval, which we first perceive in the Anteaters
and Armadilloes, (which approach to Birds by the existence
of a Cloaca,) and also in Sloths, but in such a manner
that its orifice does not form a proper Cervix, and, con-
sequently, the organ resembles the Bursa Fabricii, or a
portion of the Oviduct of Birds, rather than the human
Uterus.f Much more similar to the latter is the single
Uterus of Apes, and that not only in shape but also in the
nature of its parietes. The double as well as the bicornute
Uterus resemble a true Intestine or an Oviduct in this
respect, that their parietes are thin, but their muscular
fibres, on the contrary, very distinctly perceptible : the
single Uterus, on the other hand, and even that of Anteaters,
but more particularly of Apes and Man, has extremely
thick parietes, the muscular fibres being much less evident,
especially in the unimpregnated state. Lastly, the Makies
form a transition from the anthropomorphous structure of
the Uterus of Apes to that of the Carnivora by the division
of the fundus into two cornua ; a structure that exists con-
stantly in the Uterus of the human embryo, and occasion-
ally presents itself as. a permanent malformation in the adult.

§. 746. 4. External Organs for Copulation. In Birds

and Amphibia, the last dilatation of tl\e Intestinal Canal
Cloaca) served in the female as the external organ of

me to correspond most perfectly with the retroverted elevator muscles of the
Testicles, (Guhernaculum of Hunter,) of the origin of which we shall have
occasion to speak hereafter. It is remarkable, also, how the vessels of these
ligaments form an immediate connection between the internal organs lor
lodging the young and the external abdominal surface, where there are simi-
lar external nutritive organs (Mammae) ; which last are originally placed in
the inguinal region. The upper ligaments I consider as merely repetitions
of the lower, and they seem also to be much less vascular.

f This resemblance to Birds has been also remarked by Meckel. Trans-
lation of Cuvier.

313

Copulation; whilst, oil, the contrary, in Fishes, the urinary
and sexual orifices were distinct from the anus, but situated
behind it : in the Mammalia the urinary and sexual open-
ings are again equally distinct from the anus, but are placed
ill front of it. The Ornithorhynchus, Echidna, and
Beaver, however, are exceptions ; as in them there is a
common opening to the Vagina and Rectum. It is an
approximation to this structure that in the Tardigrada and
Edentata, according to Cuvier, and also in the Seal,
according to Meckel, the orifices of the Vagina and Anus
are very close together, and the Urethra and Vagina nearly
one canal. The latter is also the case in the Ornithorhynchi,
Anteaters, and Marsupial Animals, where the orifice of
the Urethra is close to the opening of the Uterus, and
where, consequently, the sexual appear to open into the
urinary passages ; whilst the reverse is the case in other
animals, and the Urethra opens more towards the margin
of the Vagina, as in Man. Even in the Bear and Genett-
Cat the orifice of the Urethra is still high up in the Va-
gina.* On the other hand, it is remarkable, that in Makies
it perforates the Clitoris. That organ, which is a rudiment
of the male Penis, appears to be common to the females
of all Mammalia, and exists even in the Cetacea and the
Ornithorhynchus.f It is found particularly large in the
lascivious Apes; is furnished with a bone in Cats and some
Rbdentia, and also, according to Cuvier, in the Bear and
Otter ; in the Opossum, on the other hand, it is bifurcated,
corresponding to the double Penis of the male. Lastly, we
have to notice, as important deviations in the external organs
of female Mammalia from those of the human female, the

• See Daube.vton’s Plates in Buffon’s Hist. Nat. vol. viii. tab. xii
vol. ix. tab. xxxvii. The Vagina itself in Mammalia usually presents lox
tudinal, and rarely transverse, folds.

f Home, Philos. Trans. 1802. p. 307.

344

absolute deficiency of the Nymphse and of the Hymen,
which latter, however, is compensated, though imperfectly,
by muscular contractions, or by folds of membrane in some
Species, e. g. the Manati, the Mare, Hysena, Daman,
some Apes, &c.

§. 747. 5. External Organs for the Support of the Young.

These consist of the Mammae, together with the bag within
which they are lodged in the Marsupial Animals. Both
are organs which we here observe in this form for the first
time in the animal series ; though the nutrition of the
young in the dorsal cells of the Pipa (§. 735.), and the
milky fluid secreted in the crop of Doves, are phenomena
of the same nature; whilst the whole process corresponds
to the transference of the young, or of the Ovum, from an
internal to an external organ, as is very commonly the
case even in the inferior Classes of Animals. The Mam-
mae have not yet been discovered in the Ornithorhynchus
and Echidna, though it is not improbable that they do not
appear until the young animals begin to suck; a supposition
rendered still more probable from the circumstance, that,
according to D’Aboville,* the Mammae appear to be pro-
duced in the same way in the Opossum, being, conse-
quently, placed irregularly, and disappearing-)- at the end
of the term of sucking ; besides that in most Mammalia
the nipples are first perfectly developed during pregnancy,
the corresponding glands at other times being flattened,
and differing but little from the rudiment of the same parts
in the male. The mammae differ from those of the human
female more in external form than in internal structure,
for in the latter respect we have to notice only the exist-

* Voigt’s Magazin, b. v. st. 2.

f In this point, .as well a3 in form and office, there is a great similarity
between the Mammie and the Placentae, particnlai ly the parts formed from
the Uterus, inasmuch as they also first originate in the pregnant state.

34 a

epee of larger receptacles for milk, which purpose is in the
other case answered by the nipple. The number and po-
sition of the teats, on the contrary, are remarkable, the
former ordinarily corresponding*' to the number of young,
and, consequently, of Placentae, which in the animals with
long cornua to the Uterus is considerable : the position,
on the contrary, presents in the series of animals a gra-
dual and regular recedence from the external genital parts
towards the Thorax, a circumstance which again most
decidedly reminds us of the very generally existing relation
between the sexual and respiratory organs. To give some
instances of this recedence ; in the fish-like Mammalia, the
nipples, according to Hunter, f are situated in two folds
at the sides of the Labia Pudendi. (Tab. XX. fig. XIV.)
They are placed in the inguinal region in the marsupial
animals, where they are contained within a peculiar bag
opening by a longitudinal fissure, and furnished with two
(marsupial) bones and several muscles : at the time of
parturition the aperture of this bag is brought close to the
opening of the Vagina, and receives the immature young
as they are expelled from it. The teats occupy the ingui-
nal region, also, in the Ruminants and Solipeda, and in
part, at least, in the Rodentia, where some are found on
the abdomen. They are placed upon the abdomen in the
amphibious Mammalia, and in Pachydermata, (except the
Manati and Elephant, in which they are thoracic,) and
also, or at least in part, in the Carnivora, where, when they
are very numerous, some are placed upon the Thorax.
Lastly, there is a single pair of proper pectoral nipples in
Bats, Apes, and Man.

* It is interesting to find that in animals where the ovum has several
Placenta?, there are frequently several teats to one Breast, e. y. in the Cow.

f Philos, Trans. 1787. p. 445.

346

(b.) Male.

§. 748. These are particularly distinguished from those
of the Classes immediately preceding by their more absolute
separation from the intestinal canal, the Semen and Urine
no longer passing through the Anus, but being discharged
by a peculiar canal in the Penis, which we already found
in the inferior Classes. They are more simple than the
female organs, consisting of Testicles and seminal canals,
Vesiculse Seminales and Penis, with the addition of rudi-
ments of the Uterus (Prostate) apd Mammae.

1. The Testicles of Mammalia differ from those of other
vertebral animals chiefly in their more distinctly fibrous
parenchyma, formed by the convolutions of vessels, the
softness of which is compensated by an inflection (Corpus
Highmori) of the external covering of the organ; the con-
volutions of the vessels often appearing externally in the
form of a dark serpentine line, particularly in some Ro-
dentia. The size and situation of the Testicles vary much
more in the different species than their internal organization.
The size is most considerable in the inferior species, parti-
cularly in the Rodentia, reminding us of the large Testes
of Fishes. As concerns their position, we cannot fail to
recognise an evident approximation to the inferior forma-
tions, inasmuch as in the web-footed animals, the Daman,
Elephant, Ornithorhynchus, and Echidna (Tab. XX. fig.
XI.), they are uniformly lodged, as in the human foetus,
within the abdomen close to the Kidnies. In other Mam-
malia, on the contrary, we find the Testicles escaping from
the abdomen at a certain period of life, and in such a man-
ner, that during increased sexual impulse and enlargement
of their size they again recede into the abdomen ; as is the

case in most Rodentia, e. g. Rats (Tab. XX. tier. VI. f.*),
Mice, Squirrels, Beavers, &c. and those animals that ap-
proximate to them in form and mode of life, viz. Shrews,
Moles, Hedgehogs, and Bats. In other instances they
remain permanently without the abdomen, either merely
under the skin of the inguinal region, as is the case, accord-
ing to Cuvier, f in the Otter, or of the sheath of the Penis,
e. g. in the Hog ; or lastly, as is the case in most of the
remaining Mammalia, in a peculiar sac (Scrotum) hanging
behind or in front of the Pelvis. The descent of the
Testicles takes place as in the human foetus;}: in such a
manner that they are enveloped and fixed by a reflection
of the Peritoneum, and protrude through a fissure in the
abdominal muscles into a sac like that of a hernia, formed
by the Peritoneum : when the Testicles are proportionally
very large, e. g. in the Rat, each of them with its seminal
duct is attached by a kind of Mesentery, like the Uterus
in the female. In passing through the abdominal muscles,
some fibres are detached from them, constituting the elevator
muscle of the Testicle, whilst the pouch of peritoneum
forms a canal, (Canalis tunicse vaginalis propriae testis,)
which soon closes partially in Man, but in all other animals
remains pervious, and is of extraordinary width, when, as
in the Rodentia, the Testicles recede periodically. || When

f According to him, this is also the case in the Camel, where, however,
Emmert has discovered a complete Scrotum. ( Salzb . Med. Zeit. 1817.)

\ See Seiller’s excellent Treatise, Dc descensu testiculorum, &c. 1817.

|| This process is physiologically very remarkable, and its character ap-
pears to me determinable by an analogy with the structure of the female.
The male Testicle may be regarded as an Ovum from the female body in a
higher stage of organization, the similarity of the two parts, e. g. in Birds,
having been already pointed out. As the Ovum is so generally transferred
from an internal to an external organ, though ultimately to be thrown off, so
also is it as regards the Testicle ; and it is only in a very active condition o*

348

tlie Testicle actually recedes in the animals just mentioned,
its elevator muscle together with the peritoneal sac are
inverted, exactly like the Feeler of a Snail, the former
then appearing as the Gubernaculum : and instead of the
Testicle, a funnel-shaped opening presenting itself exter-
nally, within which the muscular fibres are reflected, and
thus rendered capable of bringing about the re-protrusion
of the Testicle. (Tab. XX. fig. VI. 1.)

749. 2. The Seminal Ducts. In Mammalia, as in Man,
the excretory vessels of each Testicle unite to form a common
seminal duct, which makes many convolutions close to the
Testis under the name of Epidydimis. Its si/e is generally
proportioned to that of the Testis, and, consequently, is
extremely large in the Rodentia (Tab. XX. fig. VI. g. i.),
forming a little head interiorly, and less closely connected
to the Testicle than in Man, the union between them
being very loose, according to Cuvier, in the Opossum,
and in the Ornithorhynchus, according to Home. The
course of the seminal ducts themselves, and their insertion
into the neck of the urinary Bladder, (which reminds us
of the openings of the Uterus on each side of the bladder
in the Ornithorhynchus,) are almost precisely the same as
in Man, except that when the Testicles are lodged within
the abdomen they are more serpentine,* and their parietes

the productive functions that we again find it approximated in some animals
to the central organs of re-production. Even the point at which the Testicle
protrudes is important, because we may compare the abdominal ring to the
inguinal fissure in Bays and other Fishes, in which we found that it was chiefly
intended for the issue of the Ova; and may consider, consequently, the Guber-
naculum as the inverted and elongated margin of this orifice attached to the
Epidydimis rather than to the Testicle itself. Lastly, the fact that the
Epidydimis is surrounded by the Guheniacnhun, in the same manner as a
part of the Oviduct (the corner of the Uterus) by the round ligament, is a
proof of the truth of the analogy of the latter organ before pointed out.

* In that respect, e, g. in the Echidna (Tab. XX. fig XI. c.) they again

349

thinner. Dilatations of the seminal duets before their enJ
trance into the neck of the Bladder are found particularly
in Solipeda, Ruminants, and, according to Cuvier, in the
Elephant, and agree completely with the part which we
considered as supplying the place of the V esieulte Seminales
in the preceding Class, and even in some Fishes. They
are distinguished not merely by the increase of their dia-
meter, but also by the greater density and more glandular
nature of their parietes, and the cellular structure of their
internal surface.

§. 750. 3* Vesiculcc Seminales and Prostate. In female

Mammalia we find the Uterus, the receptacle and at the
same time the secretory apparatus for the product of im-
pregnation, formed between the Bladder and Rectum by
the swelling of the Oviducts : in males, we meet, in the
same situation, receptacles for semen and secretory organs;
and, as in both, we find an imitation of the Uterus, we
cannot but consider them as rudiments of that organ. These
parts are, like the Uterus, ordinarily divided into lateral
cornua, and vary so much in their form, that different
names have been given to them at different times, on which
account the general view of their character above proposed
appears most suited to remove these contradictions. True
Vesiculse Seminales, connected immediately with the
seminal ducts like those of Man, appear to occur in Mam-
jfialia without any particular order,*' e. g. in Apes, Bats,
Rodentia, Moles, Hedgehogs, Pachydermata, and Solipeda;
they are wanting, on the contrary, in the web-footed ani-
mals, which approach closest to Amphibia and Fishes, except

approximate to the closely convoluted seminal ducts of Birds following the
course of the Ureters.

* Haller (Elm. Phys. vol. vii. p. 455,) believes that they occur
chiefly “ quadrupedibus non valde ferocibus, neque a carne certe sola vi-
‘ ventibus;’’ but the relation is unquestionably more uncertain.

350

iri the Manati; in tile Echidna, Ornithorhynchus, and also
in most Ruminants, in the marsupial animals, and in the
rapacious animals, which, by the great developement of
their muscular system, remind us of Birds. They are pecu-
liarly large in the Rodentia; in the Guinea-Pig, for
instance, presenting two long cornua bending outwards,
and attached by a peculiar Mesentery, thus offering a
striking resemblance to the form of the Uterus in the
female : in the Rat, on the contrary, they appear more
pectiniform. (Tab. XX. fig. VI. k.) They are likewise
of extraordinary size in the Hedgehog, where they consist
of from eight to ten bundles, which it is necessary to sepa-
rate from each other, in order to discover the much smaller
urinary bladder placed among them. In other species, e. g .
Swine, they have a more glandular appearance, thus serving
to support Hunter’s view of them as secretory organs
rather than receptacles. As to the Prostate, it is proved
to be truly analogous to the female Uterus from the fact
that it exists in the males of all Mammalia; because, as
Meckel ( Notes to Cuvier’s Comp. Anat.J has shewn, the
accessory Vesiculse Seminales, as they are called, are to be
considered as the Prostate in those species where the
existence of the latter was denied by Cuvier. The form
and size of the organ vary considerably : the latter is very
striking in the Hedgehog, where there are four lobes ; in
the Ruminants, where it has occasionally been considered
as a Vesicula Seminalis; and also itsbicornute termination
in the Squirrel and several rapacious animals. According
to Cuvier, it is but imperfectly formed in the Seal and
Otter.

§. 751. 4. Penis. In the preceding Classes a peculiar

male organ of copulation was still very often wanting : in
the present, however, it exists in all the species, but in
such a manner that there is a very distinct gradation in its

structure to its form in the inferior Classes. Among the
first members of such a series is the Penis concealed within
the Cloaca of the Ornithorhynchus and Echidna; which,
from its position, and also from the circumstance stated by
Cuvier,* that it is not perforated, but that the Urethra
opens at its root into the Cloaca, very closely resembles the
Penis of Birds and Tortoises. (Tab. XX. fig. XI. p.)
Next to this structure comes that ' of the Penis of the
Beaver ;f which, being placed at the margin of the Cloaca,
discharges the urine into it, but is perforated, however, in
its whole length. Here, also, we may arrange the bifurca-
tion of the Penis, each point being furnished with a semi-
canal on its inner side, between which the Urethra opens,
a structure found in the Opossum and some other marsupial
animals, and corresponding to the double Penis of several
Amphibia. Lastly, the prickles and scales pointing back-
wards, found on the Gians of some Mammalia, e. g. the Cat'
Genus, and particularly well marked in the Guinea-Pig,
may be viewed as repetitions of similar structures which
occur more particularly on the organs of copulation of In-
sects. In general the Penis of Mammalia is in other
instances essentially the same as in Man, though in less
important points there are numerous differences. Thus, as
regards the composition of the Penis by two Corpora Caver-
nosa, which is indicated in Mammalia as well as in Man
by the two crura from which it arises, the septum dividing
the two halves is occasionally wanting, e. g. in the Cetacea,
Solipeda, Ruminantia, the Opossum, &c. : the structure of
the Corpora Cavernosa themselves can be more readily dis-
covered in the Penis of the larger Mammalia than in that

* Home, however, (Phil. Trans. Ib02.) describes the Penis in both cases
as perforated, at least for the transmission of semen.

f Bonn, Anatomc Castoris. Lugd. Bat. 1805, p. 41. Hence it is not
possible to distinguish the sexes externally.

352

of Man to consist of venous plexuses,* and not of cells
as has been shewn in the Elephant by Cuvier, and in the"
Horse by Tiedemann.-}- The Urethra is frequently sup-
ported by a peculiar bone, in which it occasionally runs as
in a groove, e. g. in the Dog. (Tab. XX. fig. XII.) This-
bone is particularly large in the Whale, and in several
Carnivora; is smaller in Apes, Cats, and Rodentia ; and
is wanting, according to Cuvier, in hoofed animals, the
Porpoise, arid the Hymna. There is frequently a cartila-
ginous epiphysis at its extremity,- which then generally
forms a large part of the Gians. Besides the manner in
which the Gians is armed, as already mentioned, it fre-
quently presents swellings or peculiar projections from its
usually conical point, e. g. in the Rhinoceros and Horse.
The Penis is- usually covered to a considerable extent bv
the Prepuce, the Gians within the latter often presenting,
a striking resemblance to the Os Uteri within the Vagina:
the Prepuce itself is in many species so closely connected
with the other integuments, that it is attached to the
perineum or abdominal surface in the form of a sheath.
Such is the case in the Rodentia ; where the orifice of the
Prepuce is close to the anus, and where the Penis in the
relaxed state points backwards, either straight, or with an
S shaped curve, though when erect it turns forwards :
there is nearly a similar disposition in Cats and Camels.
On the contrarv, the sheath of the Penis in most other
Mammalia is attached to the surface of the abdomen as far
as the umbilicus, except in the Quadrumana and Bats,
where, as in Man, the Penis is merely suspended from
the arch of the Pubes, — a position by which the structure-,

* These venous plexuses have a very remarkable resemblance to the car-
responding ones in the Uterus.

| MrCKEI.’s Arcldv. b. ii.

353

of the peculiar muscles of the Penis and Prepuce is partly
modified, and partly rendered necessary.*

(c.) Secretory Organs which are related to
the Sexual Function.

§. 752. We have before adverted to the fact that the
generative function i9 essentially excretory, from which
arises its close relation to the respiratory function, together
with the evident repetition of the respiratory organs within
the sphere of the sexual, i. e. as urinary organs ; whilst,
lastly, the sexual organs themselves, and particularly the
male, present themselves as little else than secretory
organs, though regulated by a peculiar sense. But as we
found that in the inferior Classes of Animals other secre-
tions were poured into the sexual passages in addition to
the common ones, so also is it in Mammalia, and particu-
larly in the male sex. In these secretions we discover for
the most part repetitions of those which we before found at
the termination of the Intestinal Canal : consequently, as
in those instances, we find either spherical glands, or larger
glandular sacs, (§. 526.) the former of which (Cowper’s
Glands) generally open into the Urethra, and the latter
upon the Prepuce. 1. Cowper’s Glands are wanting in
the Amphibious Mammalia, in Otters, Solipeda, some Ru-

• In the Sea-Otter the bone of the Penis is six inches long, and is sur-
rounded at its anterior extremity by a mass of cellular substance, which in a
state of erection, when injected with blood, forms a Gians, four inches long,
and six in circumference. The anterior surface then presents a deep depres-
sion, in the centre of which is the extremity of the bone of the Penis : the
Erectores are very powerful. (Home, Phil Trans . 1796, p. 385.) —
Translator.

A A

VOL. II.

354

minantSj ami in but few of the rapacious animals, e. g.
according to Cuvier, in the Bear and Racoon; inmost
other animals, particularly those in which the anal glands
are much developed, they are commonly larger than in
Man, especially in Cats, in the Hysena, several Rodentia,
See. ; and, according to Cuvier, are even much increased
in number in the marsupial animals. 2. The Glands of the
Prepuce. We may in some respects arrange under this
head the glandular bags of the Beaver,- which secrete
castor, though they are still much connected with the
Cloaca, and constitute a very evident transition from the
anal pouches as they are found in the Hyaena. To this
head belongs, also, the bag which furnishes the Musk of
the Musk Animal, (Moschus moschiferus ,) and which,
being placed in the vicinity of the umbilicus, empties
itself into the Prepuce : according to Pallas there is an
analogous bag in the Antilope gutturosa. Similar glandular
sacs exist in the Rodentia ( e. g. the Rat, Tab. XX. fig.
VI. n.) on each side of the Prepuce, and, though smaller,
in most Mammalia, and even Man. Of the same nature
are also the glands of the inguinal region in the Hare. 1 n
the female sex these glands are either altogether want-
ing, e. g. the bag of the Musk Animal, or are much
smaller.

§. 753. On taking a general review of the course of
developement of the sexual system, we cannot fail to per-
ceive that the relative position of any individual in the
animal series is expressed more definitely in this than in
the other branches of the sphere of Vegetative Life. The
cause consists, on the one hand, in the existence in this
System of a peculiar sense, the resemblance of which in a
physiological point of view to the sense of Taste has not
only been already pointed out, but is also indicated ana-
tomically by the tongue-like shape of the true copulative

355

organ ; on the other hand, in the higher character of the
sexual organism, which is the medium tor the reproduc-
tion of the whole body, and consequently also of the
superior animal structures. But, as tor the first reason,
the organ of the sense of Taste was more developed in
Man than in Animals, so also, on both accounts, the human
sexual organs attain a higher degree of developement.
We find the proofs of this partly in the disposition of the
sexual organs, which, as well by the position of the soft
parts as by that of the bony sexual cavity, i. e. the smaller
inclination of the Pelvis, (§. 277.) necessitate a mode of
copulation which occurs but rarely in other animals, and
then only as a consequence of an organization in other
respects imperfect;* partly in the increased degree of sen-
sibility, which may be traced to the more decidedly papil-
lary structure of the skin of the Gians, and to the deve-
lopement of Nymphse and stronger transverse folds of
the Vagina, the anterior and most delicate of which appears
as the token of Virginity ; and, lastly, in the structure of
the human Ovary, ( where the generative elements are ideal
rather than material,) and of the Uterus, which by its simple
globular form appears to be the determining cause of
the more perfect and spherical form of the female bosom.f
On the other hand, the perfection of the human Sexual
organism is ideal, in so far as the stimulus of sex is no
logger connected with the organ merely, but is influenced
by the beauty of the general form of the body, whilst the
rude sexual impulse of animals here assumes the nobler
form of Love.

• Thus both the Beaver and Whale probably copulate from before, in both
instances owing to the great developement of the caudal vertebrae, and in
the former likewise on account of the cloacal structure.

t Compare what has been said (§. 746.) on the character of the Breasts,
and their position upon the Thorax.

A A 2

Chapter II. Of (he Devdopement of the individual
Organism in the different Classes of Animals.

§. 754*. As it is the use of Anatomy to examine anti
point out the appearances of the forms of organization, and
of Physiology, on the contrary, to elucidate their functional
phenomena, the ^consideration of the history of the deve-
lopement of the individual animal frame, which consists
essentially in a uniformly progressive metamorphosis* be-
longs more particularly to the province of the latter (Phy-
siology), and forms one of the most difficult, but at the same
time most important objects within its range. But even
here the fundamental principles must be deduced from
Anatomy for the purposes of Physiology, of which we shall
have to examine the most important, viz. those that distin-
guish the individual animal as forming a repetition of the
order of succession in the animal series, first premising some
general observations on the formation of the animal frame
at large.

§. 755. We recognize the general similarity between
the individual developement of the animal, and the order of
succession in the series of animals, by the following parti-
culars :

I. That as the animal kingdom commences with the most
simple beings, to which the globular form, as the charac-
teristic of animality, (§. 23. 27.) appears to be eminently
peculiar, in the same manner each individual animal proceeds

357

primarily from a spherical mass, — the Ovum ; in which, as
in the seed of Plants, (§.713.) the Embryo is originally
lodged, and so far ideally that it long remains invisible
as a material object. Hence, as regards its form, the Ovum
may be in the first instance compared with the Globe Ani-
mal (Volvox), differing, however, in its internal organiza-
tion in containing the tendency to a higher formation,
constituting an ideal principle,* that, like the germinative
power of a seed may long remain dormant, but when
favoured by the concurrence of certain external circum-
stances, forms the efficient cause of the farther develope-
ment of the embryo. Hence, too, the living Ovum, i. e.
external to the body of the mother, or impregnated by the
semen, is not in itself an animal, but contains the idea of
an animal.

II. As the Animal Kingdom begins in Water, the
lowest animals being always aquatic, so also the embryo is
originally surrounded by the fluids of the Ovum.

III. As the lowest animals consist of uniform, punctiform
masses of elementary animal matter, so also does each indi-
vidual embryo in the first instance.

IV. As the lowest animals are characterised by their
imperfect self-existence and their dependence on external
objects, so also the embryo, the existence of which imme-
diately depends upon the Ovum, with which it has the
closest connections, its most important organs being external
formative organs that disappear at a subsequent period. As
forming such organs for the foetus, and also as portions of
the Ovum, we have to consider, 1. The common covering
or shell, which is a product of the Oviduct or Uterus, and
-either appears solid, and without vessels (shell), or, as a

*' As in the seed, so in the Ovum, this principle appears to be communi-
-cated by the act of fecundation alone, and consequently all the endeavours
must be fruitless, the object of which is to discover the impregnating force
as a material agent.

358

Chorion, receives the vessels belonging to the branchial bag,
and occasionally is connected (as a Placenta) with the
Uterus. 2. The Chyle-bladder (yolk-bag, Vesicula umbi-
licalis), which, as the absolute product of the Ovary, com-
poses the vegetative part of the foetus, on the one hand
forming the first source of preparation of blood, and on the
other being related to the Intestinal Canal. 3. The foetal
covering (Amnion), which, in its relation with the foetus,
presents a repetition of that existing between the Chorion
and Vesicula Umbilicalis. 4. An external respiratory
organ; which, however, is only a repetition of the inferior
formations of that kind, and therefore forms either actual
branchia?, or a branchial bladder (Allantois), representing
the excretory, as the Vesicula umbilicalis does the ingestive,
portion of the vegetative sphere in the foetus. 5. An
organ (the Funis) which forms a communication between
the embryo (the centre of the Ovum) and the external
(peripheral) structures, and consists of vessels, the organs
of communication peculiar to the vegetative sphere.

V. As the lowest animals are furnished only with the
most absolutely essential organs, and therefore present an
extremely simple structure, so also is it in the embryo of the
higher species. A few words on this point are necessary,
as it either has not been perceived or not understood by
those who deny the similarity existing between the deve-
lopement of the individual animal and that of animals in
general : when it is said that the higher animals also have
originally only the most essential organs, it by no means
follows that such organs must be identical with those of
the lower animals ; were that the case, both organisms must
subsequently continue the same, and, consequently, it ne-
cessarily follows that the primary and essential organs of
the embryo of higher animals must be altogether different
from those of the Polype, for instance : and, hence we see

359

sufficient reason, why it should happen that in the higher
part of the animal kingdom, characterized by the central
nervous masses of the vertebral column, the formation com-
mences with them, and with the animal sphere in general,
whilst, on the contrary, the vegetative organs are primary
in the inferior animals, characterized by the predominance
of the vegetative sphere,

VI. Lastly, as the individual forms of the animal king-
dom attain the utmost perfection only gradually, and in
definite series of developement, so also must the individual
animal be developed according to a given order of suc-
cession. Even this principle has occasionally been so far

mistaken, that it has been imagined that the fcetus of

Mammalia, for instance, must be first like one of the Mol-
lusca, and successively an Insect, a Fish, a Bird, without
considering; that in the Animal Kingdom there exist differ-
ent series of developement, that one series extends from
the Zoophyte to the Butterfly, another from the same point
to the Sepia ; whilst others again reach from the Fish to
the Bird, and from the Bird to the Mammalia, each indivi-
dual Organism not passing through every series of develope-
ment, but merely through those corresponding to its nature
and character, and none of the stages of metamorphosis
which it passes through corresponding precisely to any in-
ferior one, but merely agreeing with it in general import ;
for were it otherwise, they must continue to be identical.
We next proceed to the particular consideration of the
principal forms of the Ovum and the stages of develope-
ment in the different Classes of Animals; an infinitely
extensive field on which we can here trace only some ele-
mentary positions, many points being still clothed with great
obscurity, and affording inexhaustible materials for further
investigation.

360

Section I. Of the Development of Zoophytes.

756. Where the animal itself is little more than an
ovum that movos, takes in nourishment, and propagates
itself, the metamorphosis from an ovum into an animal
must necessarily be very inconsiderable. Hence, the ovum
is frequently merely a portion of the body of the mother,
detached, and continuing to exist independently : or, in
those Genera (§. 716. 717.) which evacuate Ova, the
Embryo is evolved from the Ovum in the most simple man-
ner; for it appears, from the observations of Muller,
Gade, Cavolini, and Spix, that the Embryo in the Ovum
of Medusm and Actinia?, for instance, is of a very simple
form, resembling an infusory animalcule, no other organs
of formation belonging to it than the membranes and fluids
of the Ovum itself :* a process of developement which here
appears very generally to take place before the Ova quit
the body of the mother; c. g. in the Medusa?, where they
are placed upon the arms of the animal. The young animal
ultimately breaks through its coverings in order to enter on
a state of independent existence, and when this happens
before the Ovum quits the body of the mother, or, at least,
when the young animal is at that period completely formed,
its birth is of the viviparous kind, and takes place through
the mouth. (§. 717.)f

* The Yolk-bag (Vesicula umbilicalis) and unvascular Chorion appear
litre, as in many other of the lower animals, to be the only parts forming the
ovum, the foetus being composed immediately of the contents of the former.

f The Ova of Spunges are quite visible to the naked eye, and are seen
disseminated through the whole texture of the animal. They arc bodies of

3(U

Section II. Of the Developement of Molhusca.

%, 757 . In all the Species of this Class we found true
Ovaries, the Ovum, too, generally admitting of a more
complete examination, and being developed either as in
the preceding Class within, or else external to, the body of
the mother. The form and arrangement of the Ova of
some Accphala have been already treated of (§. 719.), as
well as the situations in which they are farther developed.
Even here, however, we cannot discover organs for assisting
in the developement of the foetus, though the form of the
Embryo itself has already many peculiarities. Thus we
find the young of the River-muscle glued together in the
Gills by a viscid mucus, in which they move vigorously,
and vary considerably in shape from the adult, the situation
of the hinge (Cardo), where we found the Heart lodged,

3 yellow colour, somewhat translucent, pear-shaped, tapering more or less at
the narrow end in different species. Their whole outer surface is covered
with delicate projecting eiliae, and when viewed through the microscope in
conjunction with the parent, it is seen that the rapid vibration of the cilia;
produces a distinct current in the water around them, flowing always from
the rounded free extremity to the tapering fixed extremity, thereby, during
the period of their attachment, assisting certain little granules, which are
constantly thrown off from the parent, in producing the currents of water
observed to issue from tire orifices of the canals in the Spunge. For somo
time after they are propelled from the interior of the Spunge they swim about
by means of the cilia; on their surface, and exhibit spontaneous motions like
those observed by Cavolini in the ova of the Gorgonia and Madrepore.
They at length fix themselves in a favourable situation, lose their original
form, and become flat, transparent, circular films, through which horny fibres
shoot, soon spreading themselves out and assuming the form of file parent.
(On ant, Edinb. Phil. Journ. vol. xiii. 382.) — Translator.

362

occupying the whole extent of the back (Tab. II. fig.
XII. D.), the little shells being imperfectly closed, and
furnished on the front edge with a peculiar projection, pro-
bably an elongation of the Branchiae, or a longer feeler of
the margin of the Cloak. In the Ascidiee, where the young
are lodged on the external surface of the old animal, their
form as mere Ova is more decidedly marked in proportion
as they are smaller : they then consist merely of an external
gelatinous case, (which may be considered as the shell of
the Ovum (egg), subsequently forming the leathery cover-
ing of these animals, and continuing as such through life,)
and of an internal blackish yolk-bag (Vesicula umbilicalis)
connected with the muscular sac (Cloak) and Intestines.
(Tab. II. fig. V. IV.) It is remarkable, too, that the
young ones of a large species of Ascidiae approximate to
the smaller kinds in consequence of the close juxta-position
of the two orifices of the body, of the smaller mass of the
Liver, and the thinness of the leather-like case.*

§. 758. The Ova of the Gasteropoda are usually deve-
loped external to the body of the mother, though, as we
have already seen, the Cyclostoma viviparum has a tube-
shaped Uterus in which that process takes place. Swam-
merdam! states the following facts : the Ova in the Uterus
of the individual that he examined were of different sizes,
some more and others less developed : in one animal there
were 12, in another 14, Ova attached by one or two threads
supplying the place of a Placenta (Tab. III. fig. XII.) :
in another animal he found only one young one, and that
already hatched : the more developed ova presented them-
selves first, and those that were less so, were lodged towards
the fundus of the Uterus. lie invariably observed the
foetus floating unattached in the fluids of the Ovum, and

* Meckel's Arcliiv. b. ii. h. 4.

f Bib. Nat. p. 75.

363

.the smaller ones performing a rotatory motion. A similar
motion was observed by Stiebel* in the foetus contained
within the Ova of the Limneus stagnalis , which are deve-
loped externally to the body of the mother : in these Ova,
too, when just deposited, such as were impregnated were
distinguished by containing a yellow point, and by their
shape, which was oval, and not, as in the unimpregnated,
round. In from four to five days after it is laid, the state
of the Ovum changes : a black point appears in addition
to the yellow one ; the latter, the rudiment of the foetus,
which consists chiefly of Liver, moving constantly round
it : on the sixteenth day the pulsation of the Heart can be
perceived, and the young animal is hatched between the
20th and 30th. As regards the Ova of the Cephalopoda,
I find those of the Cuttle-fish to consist of a yellowish yolk,
and with the shape of elongated triangles with the corners
rounded oft’. Some remarkable circumstances relating to
their developement external to the body of the mother have
been described by Cavolini,-}- though already known to
Aristotle: in the impregnated Ovum, which is compared
to a myrtle-berry, we may very distinctly observe a double
membrane, and a peculiar yolk, with which the foetus is
connected by an elongation of the Pharynx, and which
diminishes in proportion to the increase of the foetus float-
ing in a peculiar fluid and performing respiratory motions:
a mode of developement which, if closely examined, con-
tradicts many hypotheses on the Physiology of the Ovum.

• Limnei Stagnalis Anatomc. Gott. 1815. It is extremely probable that
these rotatory motions serve to determine the convolutions of the Liver, ami
by that means of the shell.

f Von Erzewjung dcr Fischc und Krcbsc. s. 55.

Section III. Of the Developement of the Articulata.

§. 759. The young of Intestinal Worms are most com-
monly developed within the body of the mother,* and
born alive either within or without the Ovum, e. g. Ascaris,
Cucullanus, &e.; less frequently they are born completely
formed, but motionless within the Ovum ; and less fre-
quently still, as mere Ova, e. g. Acanthocephala, Tceniae,
&c. According to Rudolph i, the Ova of some Species,
e.g. Echinorhynchus and Cucullanus, appear to be attached
by a kind of Placenta to the Ovariesf or Oviducts; and
it is also remarkable (on the same authority), that the
Embryo of the Cucullanus is always attached to the mem-
branes of the Ovum by the posterior part of the body
elongated, consequently by a kind of Funis. (Tab. V. fig.
VII. C. D.) In these Ova, likewise, we find two mem-
branes and fluids, the Embryo by its extreme simplicity
approaching to the Zoophyte in the same proportion that
it differs from the perfectly formed animal. The same
description applies pretty nearly to the extraneous Worms,
in which the young are also generally born living, as has
already been mentioned of the Earth-worm and others.
(§. 727.) BERKENMEYERf found the Ova of the Leech
forming four Clusters, from which 150 young proceeded,
and still remained under the abdomen of the mother for
two months.

* TtuDOl.nir, Enlozoorum Ilistoria. voi. i. p. 321.
t Should not these attachments be compared rather to the Calyx of the
Ovum in Birds, than to a Placenta?

| Voigt’s Magcusin. b. iv. st. 1. s. 92.

365

§. 7G0. In the Crustacea, it has been pretty clearly
proved by the labours of Cavolini, as I have also satisfied
myself in the ova of the Cray-fish, that the little Ova
contained in the Ovary consist merely of the chyle-bladder
(analogous to the yolk and albumen of the Ovum of Birds),
around which a firm shell is formed after the Ovum has
quitted the Oviduct, and is lodged under the tail of the
animal. The Embryo is developed with the abdominal
surface curved over the yolk, the latter diminishing in
proportion as the foetus increases, and therefore, probably,
even here being taken into its abdomen, as we shall find
still more evidently the case in the higher animals. Such,
also, are probably the nature of the Ovum and the mode
of developement in Insects, the minute size of which, how-
ever, commonly prevents a complete examination: in the
tolerably large Ova of the Gryllus verrucivorus , however,
I could distinguish in the same manner an external firm
and horny shell and a finer internal one, the latter of which
surrounded the uniform, yellow, and somewhat resinous
yolk, without any trace of white, (albumen.) The same
may be observed in the larger Ova of Butterflies; an evi-
dent analogy with Birds, as we shall hereafter see, arising
from the existence of these shells, the size of the yolk,
and the extent, peculiar to this and the preceding Class, to
which the young are perfected after they have been dis-
charged from the body of the mother. To this there is an
exception only in a few inferior species, e. g. Scorpions,
Aphides, &c.

§. 761. We must, however, notice particularly the
Metamorphoses that take place in this Class after the
young animal has quitted the Ovum, and which consist
not merely in the increase, in the greater developement
and in changes of the relations of individual organs, but

3G6

present perfect alterations of form and of internal structure
as well as of mode of life ; and in thus displaying the animal
remaining for certain periods in different states of develope-
raent, present a most important and interesting series of
phenomena, which has furnished a copious subject of en-
quiry to such naturalists as Malpighi, Swammerdam,
De Geer, Reaumur, Herold, and others j but of which
we can here notice only the most prominent particulars.
Even in those Worms, e. g. the Earth-worm, where there
is a distinct Cuticle, a new one is from time to time formed
under it, and the old one thrown off: this process, however,
is more decided, when the covering is so firm as to admit
of being rejected in one piece. This is peculiarly true of
the Crustacea, where the shell of the Crab, for instance,
splits at its upper part, the animal creeping out, being as
it were re-generated from an Ovum, though without any
change of its form, and completely quitting the old shell,
the new one quickly attaining an equal degree of solidity.
The same ordinarily happens in the apterous Insects covered
with less solid horny shells, or merely by a cuticle, e. g.
Spiders, Scorpions, Scolopendrse, &c. : in other Insects, on
the contrary, the body no longer retains the shape it had
originally when it quitted the Ovum, but undergoes a more
or less complete metamorphosis. The hitter is the case in
the Orthoptera, Hemiptera, and Neuroptera, which, when
the quit the Ovum, are apterous, but ultimately appear
as winged Insects after many changes of their coverings.
The other kind of metamorphosis, where the Insect re-
turns to the condition of an Ovum, occurs in Diptera,
Hymenoptera, Coleoptera, and Lepidoptera. The Larva
here originally issues from the Ovum, like the Apterous
Insect, frequently changing its coverings as it increases in
size, and then, after having spun a soft covering and fixed it

367

to plants, &c. as to a material organ, becomes torpid as a
Pupa within it, a metamorphosis even of its internal organs*
taking place during this death-like sleep, which is ter-
minated by the eruption of the perfect Insect from its
horny shell.

Section IV. Of the Development of Fishes.

§. 762. The mode of developement of the larger Car-
tilaginous Fishes from the Ova was already known by
Aristotle, and has been farther illustrated by Monro,
Cavolini, and Home. But little is known, however, of
this process in the Osseous Fishes, where the smallness of
the Ova is an impediment to the enquiry, though there is
not any reason to suppose that it differs essentially from
that in the smaller Cartilaginous Fishes observed by Cavo-
lini. I may remark, however, that in the larger Ova of
Osseous Fishes which I examined, e. g. of the Trout, the
whole egg appeared to me to consist merely of clear and
nearly transparent yolk, almost like the Ovum of Crustacea;
Whilst, on the contrary, in the mature Ova of the Syngna-
thus, Cavolini found a yolk separate from and floating in
a small quantity of white (albumen), and having upon it
the Cicatricula, the point of origin of the Embryo. This
is still more distinct in Rays and Sharks, in which the
yolk and white are not only more decidedly separated, but

* The most important metamorphoses of these organs, viz. of the
Nervous System, Intestinal Canal, Air-passages, &c. have been already
treated of.

3G8

enclosed within a horny shell with four pointed extremities.
It has been already stated (§. 733. 734.) that the Ova of
Osseous Fishes are ordinarily hatched external to, and those
of Cartilaginous Fishes within, the body of the mother.
The foetus in Fishes in general appears to be developed in
essentially the same manner as in Crustacea. According
to Cavolini’s microscopical observations, it is formed in the
same manner upon the Yolk-bag, (Vesic. Umbilic.) around
which it is bent upon its abdominal surface, (Tab. X. fig.
XI.) and which, consequently, forms the most essential
organ to the process of its developement, the external shell
appearing merely as snch, and not yet assuming the cha-
racter of a Chorion (vascular membrane). We find here,
also, that the contents of the Yolk-bag are received from
the abdominal surface, and pass into the Intestinal Canal,
where it long remains visible, attached in the form of a
swelling (Bursa Entiana). The want of an Allantois (§.
755.) is probably supplied in the Embryo of Fishes, (and
perhaps also of the inferior animals* that breathe by
Gills) by the Gills themselves as being the permanently
existing external respiratory organ : it must be left, however,
to further investigation to determine whether the consi-
derable urinary bladder, already noticed, in some Fishes
should not be considered as the persistent Allantois, —
although it is rendered probable by what I have stated of
the urinary bladder of Amphibia, (§. 670.) Lastly, the
various modes of supporting the respiration of the foetus
are remarkable, as they have recently been observed by
FIoMEf in the Ova of Sharks: when the young are
hatched external to the body of the mother, the firm Shells,
have two lateral fissures on each side, which permit the ac-

* We have already observed that the Sepiae move the Gills even with
within the Ovum.

| On the Mode of Breeding of the Ovwiparous Sharh. PJiil. Trans. 1810.

369

cess of water (Tab. X. fig. X.) : on the contrary, when

they are developed within the Oviducts, the hard shell is
wanting, and they are surrounded by the gelatinous mass
already noticed, (§. 734.) which probably is subservient as
"well to nutrition as to respiration. (Tab. X. fig. IX.)

Section V. Of the Devebpement of Amphibia.

§. 763. We proceed first to the history of the deve-
lopement of the Frog, which, though of easy observation,
and already frequently examined, is as yet but imperfectly
known as far as regards its early periods. We have
already seen that the Ova, consisting chiefly of Yolk,
receive a covering of gelatinous matter in the Oviduct.
After the expulsion of the Ova, during which they are
impregnated, this gelatinous substance swells rapidly in the
water, and presents in its central part the blackish yolk
surrounded by a delicate membranous shell, and provided
with a little bright point or Cicatricula. The Yolk, accord-
ing to Swammerdam, consists of two halves, of which one
dppears to be analogous to the white of the egg of Birds :
upon it is formed the Embryo contained within a thin
Amnion, which, when made to protrude through the Cho-
rion by the pressure of the Yolk, was probably the part
called an Allantois by Swammerdam : the Yolk is taken
up so rapidly into the Embryo, that when the latter is
only a few lines long and barely perceptible, it is seen to
move without any Yolk-bag (Vesic. Umbiiic.) within the
Chorion, which is without vessels and not in any way con-

B B

VOL. II.

370

nectecl to it, tlie Amnion itself seemingly covering the
Embryo like a Cuticle, and, consequently, the primary ex-
ternal organs of developement disappearing at a very early
period. (Tab. XIII. fig. IX.) But as excretory, i. e.
external respiratory organs are not less indispensable to the
foetus than nutritive or vegetative organs, we meet with
external Gills (§. 603.), which, if we view the Amnion
itself as here forming the outer membrane of the Embryo,
project in the same manner between it and the Chorion as
does the Allantois in the higher animals.* During this
time it is probable that some of the external jelly of the
Ovum passes through the shell to the foetus for the pur-
poses of nutrition and respiration, in the same manner as in
the foetus of the Shark (§. 762.), inasmuch as there is an
evident diminution of its quantity during the growth of the
animal. The foetus ultimately breaks its way through the
unvascular Chorion, appearing completely as a Fish, and
having a great resemblance to a little Shark from its shape
(Tab. XIII. fig. XI.), and from the position of the mouth
on the under surface, with two little sucking tubes (fig. 3. a.)
near it : it presents within the abdomen a roll of spirally
convoluted Intestine, respires by means of Gills, and lives
on the gelatinous substance of the Ovum. Subsequently,
there is a farther metamorphosis as in Insects : the Gills
are first increased in size, are then obliterated, and for a
time compensated by the existence of a little tube on the
left side (fig. 4. c.), through which the water is respired:
lastly, the extremities protrude, the tail shrinks and dis-
appears, and the animal in the interim changing its cover-
ings several times, (and consequently throwing off the coat
formed by the Amnion,) advances from the state of a Larva
to that of the perfect animal.

* I have already mentioned that I consider the (so called) urinary bladder
as the Allantois, (§. 670.) : it is not developed until the Gills are obliterated.

371

§. 764. The progress of developement is almost com-*
pletely similar in the Land-Salamander, except that it is
carried on within the body of the mother. In a pregnant
female I found the Ova joined by a thin gelatinous mass into
a string, and lodged within the double intestine-like Uterus.
(Tab. XIII. fig. IV.) The foetus lay unattached within
the thin unvascular Chorion, which consequently was not
fixed by any Placenta: it had evident Gills, and was
capable of existing external to the Ovum, so much so that
I kept one alive in water for three weeks. The Vesicula
Umbilicalis was large, and attached to the abdomen of the
foetus, which lay curved around it within the Ovum : it was
particularly remarkable, also, inasmuch as it here clearly
formed an integral* part of the Intestinal Canal, of which
I satisfied myself in the dissection of a Larva of some size.
(Fig. XIII. 3. b. c. d.) In more advanced Larvae the
whole sac is converted into a convoluted portion of Intestine,
invariably of a bright yellow colour. We find, also, a Vein
proceeding to the Liver, which probably serves for the
absorption of the contents of the bag (Yolk), and runs ex-
ternally over the Vesic. Umbil. within the membrane
covering the surface of the Embryo, and which may here
again be considered as the Amnion : from these circum-
stances we derive an explanation of the opening of the
Veins of the abdominal coverings into the Liver, as already
noticed. (§. 701.) As regards the mode of developement
of Tortoises, I can only describe the Ova that I found in
the Mud-Tortoise : they were nearly like those of a Pigeon,

* Here, consequently, the entrance of the Vesicula Umbilicalis (Yolk-
bag) into the Intestinal Canal is most decidedly marked. Is it not also
probable, that the convoluted Intestine of the Larva of the Frog (§. 763.),
or even the spiral valve of the Intestine of Sharks and Rays, (being as it
were a convolution of Intestine consolidated into one mass,) may be struc-
tures dependent upon the Vesic. Umbil. or even formed from it?

L B 2

37 2

with a hard white shell*, a globular Yolk with a large
Cicatricula, and much White (Albumen) scarcely coagula-
ble by boiling. I did not observe any receptacle for air.

§. 765. I find the Ova of the Coluber natrix furnished
with a soft, leather-like shell, and without any distinction
between Yolk and Albumen, but containing a yellowish
mixture of the two : nor is it unimportant to observe, that
when placed in water they swelled considerably. When
hardened by spirit, I found the whole shell occupied by the
solid contents, and, consequently, these Ova do not con-
tain air, any more than those of Lizards, as stated by
Emmert and Hochstetter.* From what I have observed
in the Coluber natrix , the mode of developement in the
Ova of Serpents appears to be essentially the same as in
those of Lizards, except that, as already mentioned, they
are hatched in many instances in the Oviducts : I shall
therefore proceed to give the result of the excellent obser-
vations of the above naturalists on the Ova of Lizards. In
them, as in the Ova of the Frog and Salamander, the ex-
ternal Shell, corresponding to the Chorion of Mammalia,
is without vessels, and consists of one firm leather-like, and
two thinner, layers. Within there is contained the large
Yolk with but little white surrounding it : on it is formed
the Embryo in a distinct and permanent Amnion filled
with a peculiar fluid, but like the external shell (Chorion)
without vessels. It (the Embryo) is connected by vessels
(and not by a duct leading to the Intestinal Canal) with
the Yolk, the membrane of which is very vascular, and
within which it is probable that blood and vessels are first
formed. The excretory organ (Allantois), also, opposed
to the Yolk-bag (Vesic. Umbilic.) here appears more
distinctly : nay, the Embryo in this case being without

* Reil’s Archiv. b. x. h. 1.

373

Gills, it forms a true branchial bladder,* connected with
the Cloaca by a Urachus, and in that sense protruding from
the Cloaca in the same manner as we shall find it in Birds.
This (branchial) bladder is very vascular, and is usually
called the Chorion, although it is merely analogous to the
Allantois of Mammalia, being lodged like it, or like the
Gills of the Larva of the Frog, between the Amnion and
the outer coverings of the Ovum. During the gradual
growth of the foetus the Yolk becomes progressively smaller
and ultimately disappears, without any immediate con-
nection however with the Intestinal Canal. Such, also, is
the case as regards the Allantois, (branchial bladder,) the
Urachus of which remains in part as a small oblong urinary
bladder: the Amnion and Shell are thrown off, and the
animal is fully developed, (though not until after a con-
siderable space, the period of hatching occupying from two
to three months,) and then frequently rejects its skin,f
though without passing through any metamorphosis. A
complete investigation of the incubated Ova of the Cro-
codile would be very desirable : in a young one that had
probably but recently escaped from the Ovum, I find the
Yolk-bag (Vesicula Umbilic.) lying within the abdomen
quite full, of large size, and distinctly connected with a
convolution of Intestine.

i * The Allantois becoming obliterated in the Lizard forms a repetition of
the large urinary bladder of the Frog, in the same manner that the Larva of
the latter by its Gills, subsequently obliterated, repeats the type of forma-
tion of Fishes.

| The changes of the external covering which occur in the Amphibia
appear to characterise this Class as an intermediate transition to the higher
formations; a character, too, which the same process most evidently presents
in the inferior species of Insects.

374

Section VI. Of the Developement of Birds.

§. 766. Though there is not any process of develope-
ment that has been so frequently studied as that of Birdss
and particularly of the Chick within the egg, yet there
remain even here many dubious points to be determined.
W e shall proceed to take a brief view of the most essential
phenomena, and then point out how closely the process of
formation in this approaches to that observed in the preceding
Class. As regards the egg itself, the question has been
disputed whether the albumen deposited on its external
surface is derived from the Ovary or the Oviduct. The
former opinion* is supported by the fact, that the White,
generally speaking, is merely an appendage of the Yolk,
and must necessarily have the same origin ; and also that
in old Hens malformed Ova are occasionally deposited,
consisting solely of White. In favour of the latter,
TiEDEMANNf observes, that the mature Yolk when in the
Ovary is precisely of the same weight as when in the egg.
The Yolk, too, when in the Ovary, does not present any
trace of White, but, on the contrary, corresponds exactly
to the Yolk of the egg itself, except that it is somewhat
paler : other proofs are afforded by the concentric layers in
which the White is deposited, in which an internal and
an external portion may be distinguished, as well as by the
evident deposition of gelatinous matter around the Ova of
Several Amphibia and Fishes in their passage through the

* Advanced particularly by Joehg, in bis Grundlinien dcr Physiologie.
hfipzig, 1815, t. i. s. 236.

t Zoologic, b. iii. s. 110.

375

Oviduct. Altogether, both as regards these Ova, and also
all such as present White in addition to the Yolk, the idea
originally proposed by Harvey, and since confirmed by
Tiedemann, appears to be most correct. According to
this, the complete germ of the Ovum, with the disposition
to the formation of White (Albumen), proceeds from the
Ovary, during its lodgement in the Oviduct is nourished
by absorption, (like an Hydatid,) increases in size, and is
organically developed at the same time that its separation
into two different parts becomes more distinct. The mate-
rials that are to be thus taken into the Ovum are usually
secreted by the extremities of the vessels of the upper part
of the Oviduct, whilst, on the contrary, those of the lower
part deposit its calcareous shell.* In the Ovum of Birds
there are two circumstances, however, for consideration,
which we do not meet with in the preceding Classes. The
first of these consists in two twisted cords, placed pretty
nearly in the longitudinal axis of the egg, containing a
delicate canal opening into the yolk-bag, ramifying from each
pole of the Yolk towards the large and small extremity of the
egg, and known by the name of Chalazse, Grandines. Their
origin appears to me to depend on the separation of the
membrane of the Yolk from the external membrane of the
egg, the former remaining connected with the latter at its
two poles, and this connection being gradually elongated
Into the two tubes in question in proportion as the mem-
branes are farther separated by the interposition of new
layers of albumen, and becoming twisted by the motion of
the Yolk. The second object consists in the air-bag, which
is formed by the separation of the' two thin layers of the
membrane lining the shell at its larger extremity, and is

* This copious secretion of Carbonate of Lime in Birds and Amphibia
presents an interesting analogy with the equally abundant secretion of earthy
matter from the Kidnies.

376

accompanied by a corresponding decrease of the albumen ;
on which account it appears only after the egg is laid, and
increases nearly ten-fold* during incubation. It contains
atmospheric air, and is subservient to the respiration of the
Chick, the developement of which is completely interrupted
if it be injured.f

§. 767. The Ovum of Birds, like that of the perfect
Insects, is developed external^ to the body of the mother.
We here again find the Yolk-bag as an external organ for
the formation of the foetus, and the support of the vege-
tative processes of the body, and an Allantois, incorrectly
called Chorion, forming a respiratory organ : there are, in
addition, an unvascular Amnion surrounding the embryo,
and a membrane lining the shell, which is analogous to the
true Chorion. The progressive developement of these
parts occupies twenty-one days in the egg of the Hen, and
takes place in the following’ order. As we have already
seen, the egg is formed essentially by the membrane of the
shell (Chorion) and the Yolk with its albuminous appen-
dage. The relation between them is repeated in the for-
mation of the embryo and Amnion, which proceeds in such
a manner, that the Cicatricula, which presents itself as a
spot as large as a lentil upon the Yolk before impregnation,
and even in small Ova within the Ovary, || increasing in size
during the first day of incubation, is elongated and sur-
rounded' by some cloudy circles (Circuli, Halones). This
spot is larger on the second day, the two laminae of the

* According to Pakis. See Meckei.’s Archiv. b. i. h. 2, s. 315.

f Consequently, even in the Embryo there is already an indication of the
peculiar developement of Respiration in the Bird.

| As a morbid process the Ovum may however be developed in the Ovi-
duct, or even in the cavity of the abdomen ; of which Tiedemann (Zoologic,
b. iii. s. 145.) has given instances, and as I have myself observed.

y Tiedemann, l. c. t. iii. s. 96.

377

' membrane of the Yolk being separated in its centre, (Areola
pellucida, Tab. XVI. fig. XVII.) and the interspace occu-
pied by an aqueous limpid fluid, in which, and inclosed
within the lower lamina, (called the false Amnion,) lies
the embryo, consisting only of the most essential pare of
the hotly, viz. the Spine, with a double swelling corres-
ponding to the brain, and the Sinus rhomboidalis, and with
the cavities of the Chest and Abdomen completely open,
and turned towards the Yolk. (Fig. XVII. c.) About the
third day there are evident traces of a vascular system in
-the most important external organ of formation, the Yolk-
bag, (Vesic. Umbilic.) and in the cloudy circles. (Halones.)
In the third day it becomes still more distinct, those circles
disappearing, and a circular rete of veins (figura venosa)
surrounded by a ring-like vein, (Vena terminalis,) which
Oken* has aptly compared to the circle of vessels in the
Medusae, (§. 686.) presenting itself at the same time that
the pulsating Heart (punctum saliens) is first observed.
Hence the existence of the embryo is dependent on the
principal opponent parts of the organism, viz. the vascular
and nervous systems, the body still continuing closely
attached to the source of vegetative life furnished to it by
that of the mother, i. e. to the Yolk-bag.

§. 768. Even on the third day, but still more evidently
on the fourth, the Intestinal Canal is discoverable as a slen-
1 der thread running direct from the head to the tail, without
any perceptible cavity, and, according to Wolff, f origi-

* Zoologie, b. ii. s. 362.

| Nov. Comment. Acad. Scient. Petropolit. t. xii. p. 459. — According to
him, the Intestinal Canal is originally open in front: but is it not probable
that it appears so merely because the Yolk-bag here forms originally an
integral part of it (§. 764.), the Embryo, when examined, being separated
from the Yolk, and the anterior side of the intestine, viz. the Yolk-bag itself
*a tliat way removed ?

3T8

nating from the spurious Amnion, i. e. the inner membrane
of the Yolk. At the same time with this nutritive organ
the respiratory organ also presents itself, having originally
the form of a small vascular urinary bladder, opening, as in
the Amphibia, into the Cloaca* (fig. XVIII. h.) : it rapidly
increases in size, and protrudes as an Allantois between the
true Amnion and Yolk-bag : in the latter days of incuba-
tion it lines the inside of the greater part of the membrane
of the shell ; contains a limpid fluid, with occasionally some
urinary concretions ; and presents a beautiful net-work of
dark coloured Arteries arising as umbilical vessels from the
Iliac Arteries, and of scarlet red veins, which enter the Liver
by the Umbilical Vein: hence, also, it is a true branchial
organ, and the Chick dies forthwith if the air be prevented
by a coating of varnish from passing through the pores of
the calcareous shell. This Allantois is not obliterated until
the Chick begins to take in air by the mouth, and is ready
to break its way through the shell. The spurious Amnion
disappears on the fifth day, when we find the true Amnion
completely developed, by which means the Yolk-bag is far-
ther separated from the Chick. As to the Yolk-bag itself,
it decreases in proportion as the Allantois and Chick in-
crease: it gradually receives (probably by means of the
Chalazse) the Albumen, which is more and more compressed
towards the narrow end of the egg, and totally disappears
towards the eighteenth day, the Yolk appearing in a cor-
responding degree more fluid. The vascular net-work of
the Yolk-bag, formed by a large Mesenteric Vein and a

* The Bursa Fabricti (§. 495.) has been occasionally viewed as a rudi-
ment of the canal between the Cloaca and Allantois, (Urachus;) but were
that the case it would certainly be placed in front of the Rectum. It appears
to me to be rather an organ antagonising the Allantois on the dorsal side,
and on that account to be a secretory, i. e. a metamorphosis of a respiratory
organ. Hence, also, we may understand why it is found more vascular in
young Birds.

379

smaller Mesenteric Artery, gradually increases: from the
ninth day vve find at the extremities of the Veins pecu-
liar yellow vessels (Vasa vitelli lutea), which appear inter-
nally as flocculent cords,* and serve chiefly for the absorp-
tion of the Yolk, and for its conversion into blood, the
Chick at that time being apparently nourished chiefly in
this way, and the connection between the Yolk-bag and
the Intestinal Canal at this period at least problematical ;
for though in my own investigations I always found a loop
of intestine which is without the abdomen connected to
the Yolk-bag by means of a transparent ligament, it was
only during the latter periods of incubation that I could
distinguish a pervious canal (Ductus vitello-intestinalis)
between them. In proportion as the formation of the
Chick advances, and as the originally extensive umbilical
fissure contracts, i. e. about the twentieth day, the Yolk-bag,
which by this time is diminished in size by one half,
becomes enclosed within the abdomen, the substance of the
Yolk passing into the Intestinal Canal to be absorbed from
thence by the lacteals, in the same manner as before by the
yellow vessels (yasa lutea), and to be employed in the nutri-
tion of the young Bird. The great increase in the size of the
air-sac during incubation has been already noticed, so that
1 need only mention that in the later periods it contains
Carbonic Acid as well as atmospheric air, and that by res-
piration and perspiration the weight of the whole egg during
its developement diminishes from 16 to 13£ drachms.

• I consider these flocculent cords, particularly from examining the egg
of the Turkey, merely as duplicatures of the Yolk-bag with large absorbing
villi.

380

Section VII. Of the Developement of Mammalia.

§. 769. The developement of the Ova of some Fishes
and Amphibia within the body of the mother was in fact a
process of hatching, inasmuch as the Ovum already contained
within itself the conditions necessary for the formation of
the foetus, i. e. was furnished with a large receptacle of
chylous matter, originally derived from tiie body of the
mother. In this Class, however, there is a difference: in
the same manner that the germ of the Ovum was less sen-
sibly existent within the Ovary, so also is the Ovum less
perfectly furnished with the internal conditions necessary
for the existence and formation of the foetus, and in a cor-
responding degree requires for those purposes the interpo-
sition of a constant mutual influence between itself and the
body of the mother, — an influence that necessitates the
existence of an external formative organ around the Ovum,
and not, as we have before seen similar essential struc-
tures, within it. This external formative organ in the
Ovum of Man, as well as that of other Mammalia, consists
in its external covering, the Chorion and Placenta deve-
loped upon it, and here for that reason extremely vascular.
We here, also, find a yolk-like organ, which, very probably
in this case also, is derived from the Ovary alone, and origi-
nally forms the sole content of the Chorion, viz. the Vesi-
cula Umbilicalis: there must necessarily, however, be some
difference in its function, inasmuch as it is not originally

381

developed to its full extent like the Yolk, nor like it be-
comes gradually smaller by serving as a deposit of nutritive
matter for the foetus, but, on the contrary, in many Mam-
malia still continues to increase during the early periods of
the growth of the foetus ; besides that it is never so deci-
dedly connected with the Intestinal Canal as the Yolk ;
and, lastly, because of the very early period at which it
disappears in many other Mammalia, and even in Man
himself. * The Allantois, too, the primary respiratory organ
of the Ovum of the Bird, has totally different relations in
the Ovum of Mammalia; for here neither air nor water
penetrate the Ovum from without, and consequently the
separation of phlogistic matter (whether in the form of
excretion or expiration) must be effected by means of
a mutual action taking place between the foetus and
the body of the mother.f That function is here
assumed by the Chorion or its Placenta, f whilst the
Allantois itself appears un vascular, the umbilical vessels
connected with it at its root ramifying upon the Chorion,
and also, according to the observations of Emmert, the

• The points of resemblance and of dissimilarity between the Yolk-bag
and the Vesicula Umbilicalis have been minutely examined by Emmert.
(Reil’s Arcliiv. b. x. h. i. s. 69.) where, however, the first and important
distinction here pointed out lias not been alluded to.

f We are here reminded of what has been already observed of the mediate
Respiration of Intestinal Worms through other Animals; nor is the less per-
fectly obvious oxidation of the fluids in either case to be considered as a suf-
ficient cause for refusing to admit the existence of a respiratory process.

{ On this account the Allantois of Amphibia and Birds has been usually
called the Chorion. The two are, however, in all cases completely distinct,
and the Allantois of Birds resembles the Chorion of Mammalia merely in
being vascular. The Allantois is uniformly a perfectly closed sac continuous
with the Urachus, containing only fluid in its cavity, and is interposed between
the Amnion and Chorion: the Chorion, on the contrary, forms the entire
external covering of the Ovum, and contains within its cavity the Allantois,
Vesicula Umbilicalis, and Fcetus.

vessels of the Vesicula Umbilicalis itself opening into those
of the Chorion, which never happens in the Ovum of Birds
and Lizards. Nay, the Allantois itself becomes gradually
less and less distinct, until at length in Man it is scarcely to
be discriminated as a peculiar organ, its cavity, occupying
the space between the Amnion and Chorion, being quite
consolidated before the foetus arrives at maturity. Lastly,
the Amnion of Mammalia is in several species distinguished
from that of the preceding Classes by its vascularity, — in
which we find a repetition of the vascularity of the Chorion,
— the Amnion bearing the same relation to the foetus as the
Chorion to the Yolk or to the Vesicula Umbilicalis. We
next proceed to examine the various conditions of these
external formative organs in the different species of this
Class.

§. 770. The Chorion differs in condition chiefly accord-
ing as it performs its functions simply as such, or as it has
one or more Placentae formed upon it for that purpose.
The former is particularly the case in the Ovum of the
Solipeda, where the external surface has merely very deli-
cate tufts of vessels like those of the villous membrane of
an Intestine, with similar correspondent villi on the Uterus;
the surfaces of the Uterus and Ovum consequently adher-
ing but loosely together, and usually with a considerable
quantity of white chylous fluid between them. The little
tufts of vessels are more completely separate from each
other upon the surface of the Chorion of the Ovum of
Swine. These little Placentae, however, become yet more
perfect (and receive the name of Cotyledons or Carunculae)
in the Ovum of Ruminants, where they appear in large
numbers, from 60 to 100, as dense cup-shaped vascular
masses: corresponding to them are similar productions from
the internal membrane of the Uterus (Glandulae uterinae),
which shrink after parturition, and disappear like the Mem-

383

brana decidua of the human Uterus : the vascular extre-
mities of these productions on each side are interlocked
with each other like the fingers of two folded hands, and
when drawn asunder permit the escape of a dense chylous
fluid. (Tab. XX. fig. XVI.) In most of the animals
that have claws, on the contrary, there is but a single
Placenta,* its shape being of various kinds, but essen-
tially similar to that of Man. The following are the most
important peculiarities presented by this organ : in the
Rodentia, the Placenta again presents nearly the same
appearance of Cotyledons as in the Ruminants, i. e. is like
a deep cup or bowl, and in such a manner that it has cor-
responding to it a small distinct Placenta formed from the
Uterus: in the Beaver, it is kidney-shaped. In the smaller
Carnivora, e. g. the Mole, it is oval, and externally very
flocculent. In the Hedgehog, according to BLUMENBACH,f
it is gradually formed into a kidney-shaped and very firm
mass : in the Pole-Cat, the Placenta is double, and con-
nected by a ribband-like portion to a belt surrounding the
Ovum. In Martins, Cats, and Dogs, (Tab. XX. fig. XV.)
it is exactly in the shape of a belt. In the annular Pla-
centa of the foetus of the Dog, which has a similar flat
uterine Placenta with broad villi corresponding to it, I
remarked particularly its dark green edges, with a fluid
^ffused upon them greater in quantity in proportion to the
feize of the foetus, originally of a dark brown colour, but
in the mature foetus dark green, gelatinous, and not
affected by acids. I cannot but consider this as being an
evident separation of a large quantity of Carbon, and,
therefore, as the consequence of a true respiration by means

• The foetus of the Porpoise too, according to Bartholinus, quoted by
Tiedemann, ( Zooloyie , t. I. s. 570.) has but a single Placenta, though the
funis is divided.

• Handbuch der Vergleich. Anat. s. 489.

384

of the Placenta in the form of expiration ; and I think it
not improbable, also, that a part of the mucous chylous
fluid found about the Placenta in other animals may have
a similar origin. The Placentae of the remaining- Genera/
of Animals, particularly of Apes, resemble that of Man
still more closelv.

§. 771. As the Chorion regulates the shape of the
Ovum by forming its outermost covering, I may here men-
tion that the whole is usually, as in Man, of an oblong
round form : in such a manner, however, that in animals
with a long-horned or a double Uterus, the Placenta is
placed laterally, and not, as in Man, at its upper broader
extremity. In animals where the Uterus is single, but
lias Cornua, e . g. in the Ruminants and Solipeda, processes
of the Ovum usually extend into the cornua, which, how-
ever, as will be seen, are chiefly formed by the Allantois
extending the Chorion. The vessels of the Chorion and
Placenta pass to the foetus in Mammalia in the same manner
as in Man, though they do not form in any other instance
so long a funis. In several Roden tia and Carnivora par-
ticularly, the foetus is so closely approximated to the mem-
branes of the Ovum, and the vessels issuing from the
Umbilicus divide so speedily, that frequently there is
scarcely any funis more than in the Ovum of Birds and
Lizards. In other species, and in the Ruminants, where
it is more definitely existent, it is but of moderate length,
(in the Ruminants it is covered by a peculiar flocculent
membrane, Tab. XX. fig. 16.) and usually consists of
turn Veins and two Arteries: whilst in the Horse, on the
contrary, as in Man, there is but one Vein and two Arte-
ries. We are not as yet. enabled to decide whether there
is a true Chorion and Funis in the Marsupial Animals and
the Ornithorhynchi ; or whether, on the contrary, they are
formed after the manner of some Amphibia, e.g. the Sala-

385

wander, (§. 764.) without these organs, and are on that
account born as abortions.

§. 772. The Amnion, which in Man as .well as in the
preceding Class is unvascular, is here, as we have already-
remarked, occasionally moderately vascular, and particu-
larly in the Animals with hoofs. We may remark espe-
cially the elegantly serpentine vessels in the Amnion of the
Horse, and the peculiar yellowish scales on that of the Cow.
The shape of the Amnion is always oval, and we find it
almost always separated from the Chorion by a space con-
taining fluid, of which, consequently, it frequently fills
only about half the eavity. The interspace between the
Chorion and Amnion in Mammalia likewise affords space
for the lodgement of the sac-shaped Allantois protruding
from the umbilical fissure : that organ presents itself as a
closed bladder, shaped almost like an Intestine, and either
easily separable from the Amnion and Chorion, or closely
adhering to them on every side. The former is the case in
Ruminants (Tab. XX. fig. XVI. X.) and Swine ; the latter
in the Horse: the Carnivora (fig. XVII. i.) and Rodentia
are intermediate between both. This organ, as was already
shewn by Needham and Haller, appears to exist in all
species of Mammalia ; and even when, as in Man, it can
itself scarcely be distinguished, its existence is nevertheless
demonstrated by the presence of its fluid and of the Ura-
chus, which in some animals is very large, and in others
disappears at a very early period.* In the Dog, however,

I have succeeded in inflating the Allantois in the form of a
perfect sac, after having opened the Chorion and Amnion,
though without separating it from those membranes, which
could not have been done without laceration on account of
numerous reticular threads by which it is connected to

* This is the case in the Hedgehog, where the existence of the Urachus
was on that account denied by Blumenbach. Manual of Comp, Amt. p. 497.

VOL. II. 'C C

386

them. Its parietes are altogether without vessels, those
which take their course about the Urachus quitting the
Allantois to enter the Chorion : several branches from their
extremities, however, particularly in Ruminants and Swine,
are reflected, together with a portion of the Chorion itself,
towards the Allantois, and becoming attached to it, appear
as the parts called Diverticula Allantoidis, and by Dzondi,*
Membranse excretorise.f

§. 773. As regards the Vesicula Umbilicalis, (called
qlso Tunica erythroides,) I agree with DoellingerJ in
considering it as the most essential part of the germ derived
from the female Ovary, the first developement of the em-
bryo taking place on its surface nearly in the same manner
as we have already witnessed with regard to the Yolk-bag :
at least this is rendered probable from its being proportion-
ally largest in the smallest embryos, — from its connection
with the Peritoneum of the Foetus, — from its having peculiar
vessels like those of the Yolk, (Vasa Omphalo-meseraica,)
—and from its containing a more chylous fluid than the other
membranes. But as its communication with the Intestine,
as already noticed, is never so complete as that of the
Yolk, it appears in Mammalia to serve merely as the first
organ for the preparation of blood, and not also as in Birds
fora permanent chylous receptacle. We shall review some
of the different forms it assumes. Though it appears to
exist in all Mammalia, yet in most, and in Man himself,
it is obliterated at an early period, or at least is very
speedily changed from a bladder into a little vascular

* Supplementa ad Anatomiam et Physiologiam potissimum comparatam.
Lips. 1806.

f They have also been described as prolongations of the Chorion by
Joers. ( Grundlinicn der Phys. t. i. s. 293.)

t Meckel’s Archiy. b. ii.

membrane. The latter is especially the case in the Ro-
dentia; where, however, I find the Omphalo-mesaraic
vessels forming1 a separate cord among the umbilical vessels
at an advanced stage of the Ovum, and which has also been
observed by Emmert* in Bats. In the Ruminants, too,
it soon disappears, and in the Horse I find it small and
very much diminished towards the middle of gestation.
It is much more evident, on the other hand, in the Ova
of several Carnivora during the whole period of gestation,
particularly in Cats and Dogs. (Tab. XX. fig. XV. g.)
In the latter it is nearly as long as the foetus, (longer in the
commencement and shorter towards the end of pregnancy,)
has an oblong shape, and is situated lengthways where
the umbilical vessels enter the membranes. It is here,
and also in the Horse, uniformly surrounded to a consi-
derable extent by a duplication of Chorion, f and is attached
to it at each extremity nearly in the same manner as the
Yolk is fixed by its Chalazas. In the Horse it is placed
lengthways in the direction of the Funis. On the other
hand, it neither is, nor can be, found within the Allantois,
as stated by Oken.J

§. 774. So far then of the consideration of the external
organs of developement in the foetus of Mammalia. The
essential parts of the formation of the foetus itself coincide
with the mode of origin in the preceding Classes; inas-
much as that here also the vertebral column presents itself
* Reil’s Archiv. b. x. h. i. s. 65.

t Emmert, (l. c. p. 63,) indeed, states that it is likewise connected with
the Allantois, which, however, I have never found to be the fact ; on the
contrary, in the Ovum of the Dog I have always been able to remove the
lamina of the Chorion placed on the under side of the Vesicula Umbilicalis
without opening the Allantois. The mode of origin, too, of these two la-
mime appears to me to be very simple, the umbilical vessels escaping around
the Urachus from the Pelvis being distributed to the Chorion, partly below
and partly above the Vesicula Umbilicalis.

| Oken und Kieser, Beytrage zur vcrgleichendcn Zoologie.

c c 2

388

/ \

as the first organ, and still precedes all others in the course
of the further developement of the body ; that the animal
is here, also, primarily aquatic, appearing in the first in-
stance as a Zoophyte on account of the uniform punctiform
substance of its body; and that here, also, the formation of
external organs, of extremities, is the last part of the pro-
cess : it agrees also with that of Man as concerns the rela-
tions of individual organs, the considerable size of the liver,
the peculiar circulation of the blood, &c.

Here again, consequently, we find that the difference
between Man and Animals is but inconsiderable materially,
on the contrary, almost immeasurable ideally ; for whilst the
latter appear to be born merely in order to pursue the dic-
tates of Instinct, and the gratification of their propensities,
to Man, on the contrary, are imparted a capacity for the
most perfect intellectual developement, and the suscepti-
bility of Art, Science, and Religion.

APPENDIX. N°* I.

A FEW OBSERVATIONS ON THE DISSECTING
AND PREPARING OF THE BODIES
OF ANIMALS.

Though the art of anatomising the bodies of
Animals is essentially the same as that practised upon the
body of Man, and though want of space precludes me from
treating the subject minutely, I conceive that a few re-
marks may not be altogether unacceptable to those who
feel desirous of pursuing such studies for themselves.

The first thing that I have to observe is, that all dissec-
tions of small and soft objects, e. g. Worms, Zoophytes,
Insects, Mollusca, and Embryos, where it is desirable to
obtain even tolerably accurate results, should be performed
under water , by which the parts are kept floating and
separated from each other, and, consequently, present
themselves more distinctly. A very simple contrivance for
investigations of this kind may be prepared in the following
manner: — A mass of tough wax (not too soft) is to be laid
upon one, or more, porcelain saucers or capsules of different
sizes, which are then to be put in a warm place until the

390

wax melts so as to cover the surface evenly to the depth of
2 or ^ of an inch. If the object to be examined be laid
upon this surface, it may be fixed by needles in any posi-
tion that is wished, and, when covered with clear water,
developed and dissected by means of suitable instruments.
Of them, the best are very delicate Forceps; pointed, well
made, sharp-cutting Scissars; and small Knives like Cata-
ract-needles, some round, others with cutting edges, and
fixed in slender wooden handles. For separating parts I
have also employed small horn probes and fine brushes ;
whilst, for examining them, a good magnifying glass is
frequently indispensable. If it is wished to preserve a
preparation thus made, wax, coloured at pleasure as for the
purpose of injections, is to be formed into little Tablets
about \ of an inch thick: one of these is then to be placed
upon the saucer or capsule containing the preparation ; the
latter may then be transferred to it, arranged suitably upon
it, fixed there by means of short needles, and both toge-
ther then placed in Alcohol. Nor must I forget to men-
tion, that the examination of very delicate organizations
may frequently be conducted with greater facility and
accuracy, if the object be previously allowed to remain
some' time in Spirit, and thereby to become harder and
contracted. This applies particularly to the dissection of
nervous organs, and to the examination of very small Em-
bryos, of Mollusca, and Worms.

There are various modes of destroying Worms, Insects,
Mollusca, &c. for the purpose of dissecting, without injur-
ing their organization : Mollusca, Snails, for . instance, as
Swammerdam has remarked, are to be allowed to die in
water, because by that means their body swells, and all the
parts become more distinctly visible ; they may afterwards
be kept in Spirit (though not too long) for dissection.
Worms, the larger Zoophytes, (for the smaller must be

391

examined whilst alive,) Caterpillars, &c. and also the
smaller Amphibia and Fishes, are best destroyed by means
of Spirit: Insects, on the contrary, by beings dipped rapidly
in boiling water, or in Oil of Turpentine.

As regards the dissection of larger animals, we may here
use with advantage knives of a large size, and instead of
Forceps, suitable hooks with handles.

In animals of considerable size we can generally make
artificial skeletons only, after the bones have been suffi-
ciently cleaned by boiling or maceration. In smaller
animals, on the contrary, such as Birds, Amphibia, and
Fishes, of which last it is very difficult to make good skele-
tons, the object will be best accomplished by at once making
the bones as clean as possible, without injuring the capsular
ligaments, soaking the preparation in water that is inces-
santly changed, and, lastly, bleaching it for some time in
the sun.

Lastly, we may mention injections as affording a very
essential assistance in zootomical investigations for physio-
logical purposes : in small animals, and in the more minute
parts, these must consist of compositions with wax, very
fluid and coloured ; but above all of Mercury. The latter,
however, is not suitable for very soft bodies, e. g. Medusae,
&c. in which cases we may employ injections of coloured
milk, and similar substances.

APPENDIX. N° II.

DISCOVERY OF A CIRCULATION IN

INSECTS.

An Essay by M. Carus,* which has appeared whilst
the second volume of this Translation was in the press,
contains the particulars of his discovery of a Circulation
in certain Insects; a circumstance that may safely be cha-
racterized as by far the most important addition that has
been made to Comparative Physiology in modern times.
The observations on which it is founded were made in the
autumn of 1826, and an abstract of their results presented
in September of that year to the Union of German Natu-
ralists and Physicians, which then held its meeting at
Dresden, many of the members of which, e. g. Oken,
Huschke, Heyne, Purkinje, Otto, Weber, and Mul-
ler, had ocular proofs of the reality of the phenomena.

• His first observations were made upon the Larva of the
Agrio n puella, which swims with great velocity by means

* EnJdecfnincj cities einfachen twin Ilerzen aus bcschleuniglen Bhithreislanfes
in den. Lancn netzJUiyliclter 1 nscctcn . INI i t drei Kupf. taf. Leipzig. 1821.

393

of three vertical laminae attached to the caudal extremity,
and diverging from each other at very acute angles. In
the young Larva there is not any trace of wings, but as it
advances in age rudiments of wings make their appearance
over the rings of the thorax, and gradually increase to
their full size, whilst the caudal laminee, on the contrary,
in the same proportion fade away, and are partially or
completely detached. Each of the caudal laminae in its
natural vertical position presents an inferior abdominal, and
a superior dorsal, edge, has two tracheal trunks running
along its centre and ramifying through it, and consists of
granular substance contained between two strata of the
external integuments. A current of blood-globules enters
each caudal lamina somewhat nearer to its abdominal than
its dorsal edge, and running through the greater part of its
length, suddenly turns and bends its course back towards
the body somewhat nearer to the dorsal than the abdominal
margin of the lamina. The path or channel thus formed in
the midst of the granular substance is perfectly transparent,
except where it is occupied by the blood-globules, or
crossed by branches of the Tracheae. The parietes of the
channel are not strictly defined, nor formed by any thing
like the coats of a vessel, the blood with its globules cir-
culating through the granular parenchyma, a circumstance,
however, which is not peculiar to this case, but also occurs
i generally in the first states of the circulation, as it presents
itself, for instance, in the embryo of Fishes, and in the
Figura venosa of the incubated Egg. The blood-globules
are elongated, like a grain of wheat, considerably larger
than those of the human blood, and float in a fluid, which
is invisible because of its transparency, but the existence
■of which is proved by the variations in the position of the
globules in the current, sometimes following its direction,
at others crossing it transversely or more or less obliquely.

294.

When the animal is vigorous, this current is unceasing
and uninterrupted, although its velocity is accelerated at
regular intervals, and that not only in the abdominal or
excurrent, (arterial,) but also in the dorsal or recurrent,
(venous,) part of its course through the lamina. When
the animal becomes exhausted, or the caudal laminae ex-
siccated, the circulation through them is interrupted, and,
in the same manner as under the same circumstances in the
Larvae of Frogs and Salamanders, the disturbance displays
itself not merely by a cessation of the process, but also by
retrograde movements of the currents, or by oscillatory mo-
tions of the blood-globules.

In proportion as the wings are developed, the circulation
in the caudal laminae diminishes, and ultimately ceases,
preparatory to the detachment of the laminae themselves.
At the same time, however, the circulation presents itself
under a new form in the wings themselves. These organs
consist of two layers of the integuments, including between
them a collection of granular substance divided like net-
work into little islands by the intersection of transparent
canals, the largest of the canals taking its course round the
margin of the wing, and the whole organ being interspersed
with minute Tracheae. These canals present a circulation
similar to that in the caudal laminae, the excurrent (arterial)
stream taking its course along the inner margin of the
wing, and the recurrent (venous) returning along the
outer; whilst occasionally other transverse currents take
their course through the. net-work of the wing from its
inner to its outer margin. As the wings are farther deve-
loped, the circulation in them, like that in the caudal
laminae, gradually becomes weaker, and ultimately ceases.

The next observations were made on the Larva of a
neuropterous Insect, (probably a Semblisor Sialis, ) the body
’ of which was sufficiently transparent to admit of being satis-

395

factorily examined by the microscope'. The dorsal vessel
was seen distinctly pulsating’, but principally at one point,
viz. its posterior extremity, the motion in the anterior part
being merely propagated to it from the posterior ; these
two divisions of the dorsal vessel having the relation to each
other of a Heart and Aorta. Excepting the dorsal vessel
there were not any traces of regularly defined blood-vessels
in the other parts of the body, although regular currents of
blood-globules presented themselves with the following
appearances. On each side of the body, and external to
the great lateral tracheal trunks, a rapid and continuous
current of blood-globules presented itself, consisting, as in
the former cases, of a succession of single globules, and
proceeding from the head towards the posterior extremity
of the body, where each of the currents entered the Heart
or posterior part of the dorsal vessel, which again propelled
its contents with accelerated velocity through the anterior
part of the vessel towards the head. The lateral currents,
also, presented an accelerated motion corresponding to each
contraction of the Heart, and proving that they must com-
municate at the anterior part of the body with the dorsal
vessel, though the opacity of the head of the animal was
such as to render it impossible to ascertain the mode of
• anastomosis. At the point where the legs were inserted
into the thorax on each side, the lateral current bent out-
wards in order to penetrate the substance of the upper
phalanx of each leg to a certain extent, and again returned
to the body, thereby forming a loop corresponding to the
insertion of each leg.

The aquatic Larva of the Ephemera vulgata , according
to M. Carus, presents the phenomena of the circulation
with still greater distinctness than the preceding animals,
and even more clearly than it is possible to recognize it in
the Lame of Frogs and Salamanders. In it the circulation

396

is at once visible (with the microscope) in the three last
segments of the body ; but by a little attention is discover-
able, not only in the three terminal caudal spiculie and in
the upper phalanges of the legs, but also in the head, and
particularly in the roots of the antennae. In the posterior
part of the body there are on each side two currents of
blood, not bounded by any regular parietes like those of
vessels, situated on each side of the intestinal canal, and
rather towards the abdominal surface of the animal : of
these two streams on each side, the outer is the smallest,
and the inner the most considerable. The external one
resembles the lateral current in the Larvai already described,
and communicates with the internal by several intermediate
branches : it is probably from this one, too, that the lateral
streams are detached in the form of loops into the upper
phalanges of the legs, though it is not possible precisely to
ascertain this point, nor even whether the two lateral cur-
rents on each side continue distinct in the thorax, which it
is most probable that they do, as the current in the upper
phalanges of the legs is of the same size as the external
of the two which appear in the posterior part of the body,
from which the internal differs by its greater size. At
the ninth abdominal segment of the body these two lateral
currents on each side, which flow posteriorly from the head
towards the caudal extremity of the body, change their
direction, and are inflected so as to enter the pulsating
heart, from which the current of blood is again impelled
towards the head. Before the lateral currents enter the
heart they give off three streams, one for each of the three
caudal spiculse, running through the greater part of the
length of each spicula, and being then suddenly reflected
towards the heart. It is not possible to ascertain precisely
from which of the two lateral currents of the body these
caudal streams arc detached, though most probably lrom the

397

external : that they come direct from the heart is impro-
bable, as the excurrent (arterial) division of each (caudal)
stream corresponds to the abdominal surface of the spicula,
and the recurrent (venous) to the dorsal, the heart being
situated on the dorsal, and the lateral currents on the abdo-
minal, aspect of the body. The currents in these caudal
spiculae present the phenomena of the circulation with pe-
culiar distinctness, and are particularly remarkable from the
circumstance that the excurrent and returning streams,
though in close approximation, and not separated in any
visible manner, continue to flow without disturbing each
other. The excurrent stream is accelerated at regular
intervals, corresponding to the pulsations of the heart ;
the recurrent, on the contrary, being always somewhat more
sluggish, and the first to stagnate and cease when the
strength of the animal is impaired.

When the extremity of one of the caudal spiculse is cut
through, the blood-globules are expelled in some quantity
with an evident jet, and accumulate on the injured sur-
face, where, when they are dried up by exposure to the at-
mosphere, they change their natural limpidity for an evident
apple-green colour.

It has been already mentioned that the heart propels its
contents through the anterior part of the dorsal vessel
towards the head: the current, however, in the thorax and
in the upper part of the head is concealed by the opacity of
the horny segments of the cutaneous skeleton, and by the
contents of the stomach. In the anterior part of the head,
however, we can discover currents in the roots of the An-
tennae, forming loops like those in the legs, the current in
each proceeding from the cranial surface of the head, and,
in returning through the root of the Ahtennae, taking its
course towards the laryngeal region. Nay, by means of the
direct light of the sun thrown on the object, an indistinctly

398

defined, but very evidently existing, current may be traced
forwards through the thorax and over the upper part of the
head, and may be seen to be reflected towards the posterior
part of the body in the laryngeal region. Hence, conse-
quently, this Larvee presents the first instance in which it
was possible' to trace a true and perfect circulation through
the whole body.

The endeavours of M. Carus to discover any evidence
of a circulation in fully developed Insects, e. g. House-flies,
Gnats, Ephemerae, &c. were without success until a very
recent period. (May, 1827.) On examining the wings of
the Semblis viridis, immediately after its metamorphosis
from the Larva state, he discovered the circulation through
all the vessels of the wings with the utmost possible distinct-
ness. The wings were still soft, but perfectly developed
for flight : the circulation was still visible, though in a less
vigorous state, two days afterwards, when the animal died.
Still more recently he has observed currents of blood in the
Larvae of Water-Beetles, (Hydrophilus and Dyticus,) and
adds, from a notice by A. V. Humboldt of the travels of
Ehrenberg and Hemprich, (in Africa?) that those natu-
ralists have also observed similar currents in the wings of
a Mantis. Hence it follows, that even at this early period
of the discovery, a circulation has been detected in four
Orders of Insects, viz. Neuroptera, Coleoptera, Diptera,
and Orthoptera ; a circumstance that afibrds the strongest
excitement to farther investigation in other Insects, and
under various circumstances.

Of the objects and character of this circulation little can
at present be said : its existence, however, in the rudiments
of wings tends in a very remarkable and unexpected man-
ner to confirm the idea deduced by Oken from analogical
considerations, and already quoted in a former part of this
Treatise, (§. 149.) viz. that the wings of Insects are ex-

399

siccated Gills. As regards the cessation of Circulation in
the perfect Insect, or rather its limitation to the dorsal
vessel, M. Carus endeavours to show, that though an ex-
treme instance, there are analogous cases, in which, though
of less extent, a circulation that once existed no longer
presents itself in the fully developed state. Thus, the
medulla contained in the cavities of the bones of young
Birds disappears as they advance to full developement, and
with it the vessels by which it was supported. Such, al^o,
is the case with their feathers, which in the early periods
of their formation are exceedingly vascular, and thus, pro-
bably, connected with the respiratory function. So, also,
in the Foetus of Mammalia, the allantoid circulation dis-
appears, and its vessels are obliterated in proportion to the
developement of pulmonary respiration. The fact that
the currents of fluids in the Larvse of Insects are not de-
fined by vascular parietes, enables us to comprehend the
rapidity and facility with which the traces of the circulation
are lost in the perfect Insect. On the other hand, the
existence of a circulation at one period, and its cessation
at another, elucidate many circumstances connected with
the physiology of these animals ; for instance, the contrast
between the rapid growth and transformations of the Larva,
and the stationary existence of the perfect Insect; the
{ inconsiderable size to which the body attains in this, as
compared with other Classes of animals ; the frequently
very short duration of the existence of the perfect Insect
in proportion to the prolonged periods of its Larva state ;
its almost total independence of nutrition; and the absence
of the power of re-producing parts that have been lost or
destroyed.

It still remains to determine at what period of develope-
ment the phenomena of the Circulation first present them-
selves ; to observe more precisely its occurrence in other

400

Orders and Species, particularly those where the Larva is
not aquatic, and where, perhaps, it exists only in the Ovum ;
to fix the period and manner of the cessation of the cur-
rents of blood ; and to distinguish, on the one hand, the
cases where the Circulation may be supposed to cease even
in the Larva state, or, on the other, to continue in the
perfect Insect.

Lastly, it may be remarked that the phenomena of
this Circulation, so far, at least, as it has been traced, do
not throw any light on the obscure subject of the mode of
nutrition in perfect Insects; which-, therefore, must still be
supposed to be effected, according to the idea of Cuvier,
without the intermedium of vessels. On the other hand,
the demonstration of the original existence, and subsequent
cessation of a Circulation, renders more than ever unte-
nable the hypothesis lately suggested by Dr. Kidd, [Phil.
Trans. 1826.) that the Tracheae, already recognised as
respiratory organs, are, at the same time, employed in the
conveyance of nutritive fluids.

finis.

PRINTED BY RICHARD CRUTTWELX,
ST JAMF.s’s-STREET, BATH.

• 4

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Full text of "An introduction to the comparative anatomy of animals : compiled with constant reference to physiology, and elucidated by twenty copper-plates"

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