the animal series. In addition to this, the gastric
character of this cavity, and the unfitness of a giz-
zard for solvent or digestive functions, further justify
us in preferring the above interpretation.
t The Tetrodon mola.
+ In the Tench (Cyprinus tinea), they are striped.
Reversing their ordinary arrangement in the
Mammalia.
|| As in the Branchiosfoma.
are, either an increase of length, which is some-
times accompanied by a diminution in width ;
or an equally real increase of active surface,
which is due to the development of folds, such
as the spiral valve of the Shark.
The appendices pyloricce, or pancreatic
follicles, are absent in many fishes. They
vary in number from one to two hundred.
In structure they range from simple, short
canals, to elaborate branches, which are united
by areolar tissue and vessels, and are enclosed
in a muscular tunic.
The alimentary canal of Reptiles preserves
much of the simplicity, width, and shortness,
seen in that of Fishes. But it offers important
differences in many respects. The thick,
semi-transparent, gelatinous-looking intes-
tinal parietes generally possessed by the Fish,
are strongly contrasted with the thinner and
more condensed and opaque tube present
in the Reptile. Such a comparison seems
to indicate a great advance in the develop-
ment of the Reptilian digestive canal. This
advance, though no doubt correlative with that
of the tissues generally, probably depends
chiefly on the increased efficiency of the respi-
ratory function.
The (esophagus varies greatly in size and
appearance. It is usually large and dilatable.
In the Ophidians this width and laxity
are so greatly increased, that it forms a tube
which can be distended to almost any extent ;
and the parietes of which are so thin, that
they may be regarded as supplanted by the
muscular parietes of the belly itself.
The stomach rarely possesses any well-marked
cardiac constriction. Hence the characters of
its mucous membrane are the chief means by
which it can be distinguished from the oeso-
phagus. Its form, in the Chelonian and Ba-
trachian divisions, somewhat resembles that
seen in many fishes. Beginning by a dilated
cardiac pouch, it tapers away towards the py-
lorus, taking a curve like a siphon. In the
Crocodiles, the stomach may be regarded as
consisting of two portions. Of these, the first
is a gizzard : which resembles the form and
appearance of that of the Cuttle-fish ; and con-
sists, like it, of a plane of muscular fibres, that
radiate from a central tendon on each side of
the organ. The second is a small pyloric
pouch or diverticulum, which passes out of
the gizzard at its upper part, close to where
it receives the dilated oesophagus. In many
Serpents the pyloric extremity is so narrow
and muscular, that the organ has been distin-
guished into two parts : an upper, or cardiac,
which is thin and saccular ; and a lower, or
pyloric, which is narrow, strong, and tubular.
The pyloric valve varies in development. But
even where best marked, it never approaches
the distinctness seen in man and the higher
Mammalia. It consists, as usual, of a pro-
jection, which is formed by the circular
muscular fibres, and is covered by a fold of
mucous membrane.
The intestine is short, and rather wide. It
is usually divided into small and large by a
circular constriction or valve.
STOMACH AND INTESTINE.
301
In the Batrachian division, however, the
separation into these two segments is some-
times absent, ^^ ^ hile sometimes, as in the Toad
and Frog, there is a distinct large intestine,
into which the smaller portion opens laterally,
so as to form a caecum. In the former of
these two genera there is no valve.
In the Ophidian the two portions are
generally distinct and short. But their relative
extent varies considerably : the small intes-
tine being sometimes lengthened, and often
presenting a very peculiar appearance in the
shortness of its mesentery and the closeness
of its folds. The indistinct ilio-caecal valve is
chiefly marked by a change in the diameter of
the tube. The large intestine is often sub-
divided into distinct portions by one or two
transverse valves.
In the Chelonia the intestine is longer and
much more muscular. There is generally
an ilio-caecal valve, and often a well-marked
cxcum. The valve is also present in most
of the Sauria. But in the Crocodile the cae-
cum is absent.
Birds. In this class, the stomach is generally
complex; being separated into three distinct
cavities, which differ greatly in their form,
structure, and office.
The oesophagus, which leads to the first
of those cavities, has a length corresponding
to that of the neck which it occupies. Its
width and dilatability mainly depend on the
nature and form of the food. Thus, in some
of the birds of prey, or those which swallow
large fish entire, it is very lax and dilatable.
And in this respect, as well as in the direct con-
tinuity of its cavity with that of the stomach,
it offers a great similarity to the gullet of
the Ophidian reptiles and many fishes. Its
mucous membrane is follicular, and folded
longitudinally.
The ingluvies, or crop, is a dilatation of the
oesophagus, somewhere about the middle of
its length. In some of the smaller Rap-
tores it is but small ; in the larger and more
voracious it is a considerable enlargement,
that affects one side of the tube more than
the other ; in the Gallinaceans it is a distinct
sac, appended to the canal by a narrower
neck ; and, finally, in the Pigeons, it attains
its maximum size, and becomes double. Its
muscular and mucous membrane are similar
to those of the oesophagus. The food which
it contains undergoes a kind of insalivation
and maceration. And the highly-developed
form of crop, which is seen in the Pigeon,
pours out a milky fluid during that period
of the year in which this bird feeds its young
by regurgitation. At this time its mucous
membrane also acquires a thicker and more
glandular character.
The proper stomach, or proventriculus, com-
municates with the inferior part of the oeso-
phagus, and corres'ponds, both in structurelmd
function, with the true stomach of the Jfani-
malia. The glandular tubes which open on its
free surface secrete a fluid that possesses all
the properties of gastric juice. In the degree of
complication these glands differ considerably ;
varying from simple tubes in the carnivorous
birds, to tubes that open between prominences
and prolongations, and finally form primary
and secondary branches. The shape and size
of this organ are subject to great variety in
different genera. In those that swallow a
large prey, it is wide and straight, like the
stomach of the Serpent. In others, it ap-
proaches the spherical form, or passes towards
the right side to join the gizzard. The com-
parative size of these two organs also varies
considerably.
The gizzard is a flattened ovoid of highly
muscular texture. It is lined by a dense
horny cuticle, and contains sand, gravel, or
other hard inorganized matters, which are the
passive agents in the trituration of the food.
Its size varies greatly. Its apertures both
occupy the upper part of the organ, so thai
its cavity terminates below in a blind ex-
tremity. Its walls contain a variable amount
of muscle, the arrangement of which is usually
that of the radiation of fibres from a central
tendon, such as was previously noticed in
speaking of the Cephalopoda. Its epithelium
is hardest in the granivorous birds. And even
in the same individual, it offers an increased
density at the precise situations of most
pressure. In like manner, Hunter noticed
that a thickening, both of cuticle and muscle,
was produced by feeding a Sea-gull upon grain.
The pyloric valve is, as a rule, well marked.
In some species there is a small supplementary
cavity, which immediately precedes it, and
receives the orifice of the gizzard.
The intestine has a length about midway
between that of the Reptilian and Mammalian
bowel. But although longer than in either of
the preceding classes, it retains considerable
simplicity of form. It presents, however,
much variety, both in its length and in the
number and appearance of its convolutions ;
differences which, as usual, are related (though
not very closely) to the food and habits of the
animal. The duodenum which immediately
follows the pylorus has the form of a long
loop or fold, the concavity of which includes
the pancreas. The small intestine, more or
less folded, terminates in a large intestine, the
commencement of which receives two caecal
tubes, one on each side. These caeca offer
remarkable differences in length : vary ing from
papilliform offsets, as in the Solan-goose, to
processes three feet long, as in the Grouse.
Sometimes only one is present. The short
and straight large intestine is continued from
the termination of the small intestine, without
any distinct valve, to end in a cloaca com-
mon to the digestive, urinary, and generative
organs. Connected with the small intestine
is an appendage, supposed to be a relic of
the duct of communication between the
yolk bag and intestine of the chick. It is de-
void of a muscular tunic, and in some birds
equals or exceeds the size of the caeca them-
selves.,
Mammalia. The form, length, and arrange-
ment of the alimentary canal vary so much
in the different orders of Mammalia, that it
302
STOMACH AND INTESTINE.
will be necessary briefly to state its pecu-
liarities in each.
In the Canrivora the shape of the stomach
approaches that of the human organ : it has
a cardiac pouch, and a greater and lesser
curvature. The intestine is short, its
length being to that of the body as* 5 to
1 in cats and dogs, and 8 or 9 to 1 in the
hyaena and bear, but reaching 15 to 1 in the
Phoca vitalina, one of the amphibious seals.
The mucous membrane is destitute of folds.
The convolutions of the small intestine are
few and simple. The caecum is short, and
scarcely wider than the rest of the large
intestine.f And the latter segment of the
canal is short, wide, and cylindrical.
The Insectivora have a very similar intestinal
tube. The simple and elongated stomach is
transverse to the axis of the body. In some
genera, its spherical cardiac pouch is enlarged,
while its lesser curvature becomes shortened.
The intestine is short from three to six
times the length of the body ; it has no
caecum, and a nearly uniform diameter. Its
mucous membrane exhibits zig-zag folds,
which run longitudinally throughout its whole
length.
In the Cheiroptera three chief varieties of
stomach have been distinguished by Cuvier.
The first approaches that seen in the preceding
order, and belongs to those members of this
group which feed upon insects. Here the
nearly spherical organ has a cardia and
pylorus, which are situated close to each
other. The second form is seen in those
which subsist by sucking the blood of animals :
it differs from the preceding in being longer,
and more conical from cardia to pylorus.
The third, which obtains in the frugivorous
division, is very different from both the pre-
ceding.
Thus, in the Pteropus the stomach is a
long tube, placed transversely to the axis of
the body. One-third of its length is formed
by the cardiac pouch, which lies to the left of
the cesophageal aperture, and is divided into
two bv a slight constriction, while its terminal
or pyloric third is bent back so as to be
parallel and near to the middle portion. The
mucous membrane of this stomach is folded
longitudinally ; the left subdivision of the
cardia is smooth, and the lower part of the
oesophagus which is somewhat dilated
differs from the upper.
The pylorus is well marked in all the
Cheiroptera, and the intestine, which is much
narrower than the stomach, and is devoid of
caecum, is of nearly uniform diameter. It
often presents concentric windings or coils.
Its length varies greatly ; thus, in the frugi-
vorous Pteropus it is six or seven times, in
the insectivorous Bat only twice, the length
of the body.
Edentata. The stomach of this order
differs greatly in different genera. Most of
them possess a simple organ ; the cardiac
* We owe these measurements to Meckel.
j- In the dog it is convoluted.
pouch of which is large and globular, while
the pyloric extremity is conical, and is some-
times almost absorbed into the spherical
cavity. A single genus, the Mains, adds a
further distinction to these two parts in the
shape of an internal fold of mucous mem-
brane ; and one of its species exhibits a long
blind sac, springing from the right of the
pyloric aperture. In the Tardigrade genera
the stomach assumes much of the complexity
seen in the Ruminantia. For it has two cavities,
a cariliac and a pyloric, which, if regarded
from the exterior, look like mere exaggera-
tions of the distinction mentioned above,
but, when examined internally, are seen to be
divided by prominent folds, and by differences
in the character of their mucous membrane.
Thus the cardiac pouch has a dry epidermoid
lining, and is subdivided by a fold into two
parts, and prolonged into a short blind tube,
while the pyloric sac has a soft and delicate mu-
cous membrane, and more muscular parietes.
And its interior is also subdivided, by a fold
of membrane, into a terminal part, which is
analogous to the fourth stomach of the Ru-
minants, and an intermediate cavity, which
resembles the third stomach of the same
order in its possessing dentate processes, and
a direct communication with the oesophagus.
The latter tube also exhibits a cul-de-sac,
which is sometimes further divided by folds.
The form and length of the remainder of
the canal is subject to great variety. Its
mesentery is very long. In many genera
there is no distinction of the intestine into
large and small. In some there is no trace
of a caecum. In others there are two of these
tubes, which occupy the confines of the lanje
and small intestines, and open by what are
sometimes extremely minute apertures.*
The Ruminantia are remarkable for the com-
plete subdivision of their stomach into four dis-
tinct cavities. The first of these, the rumen, or
paunch, is generally of very great size. It is
situated to the left of the oesophagus, from
which it receives the food when first swallowed :
it has a villous texture, but its minute conical
processes are covered by a dense white pave-
ment epithelium. The second cavity, the
honeycomb or reticulum, is so called from the
appearance of its mucous membrane, which,
in all other respects, has the same structure
as that of the preceding cavity. The third
portion, the maniplics or psalterium, is named
from the many longitudinal plies or folds
which occupy its interior. In the Camel, the
circumference of the cells or excavations
of its reticulum and paunch have been long
recognized as containing muscular fasciculi,
the contraction of which enables these cavi-
ties to retain water free from admixture with
the general contents of the stomach. And
* In such a case they can hardly be supposed to
receive faecal matter. But in the Dasypus muste-
linus, the ileum ends by a slit between the larger
apertures of two such tubes ; and hence appears to
admit of being closed by the lateral pressure of their
contents. (See Prof. Owen's Catalogue of the Hun-
teriau Museum, vol. i. p. 219. 729 A.)
STOMACH AND INTESTINE.
303
eight or nine years ago, the author discovered
that all these projections from the surface of
the ordinary Ruminant stomach, viz. thevilli,
honeycombs, and plies are constructed chiefly
of unstriped muscular tissue, lined by scaly
epithelium. The uses of such a structure are
too obvious to need any comment. The
fourth cavity or abomasum, is the true stomach :
it secretes* the gastric juice, and possesses
the ordinary tubular structure. As regards
the uses of these cavities, the bolus is probably-
moulded for rumination in the honeycomb,
and is thence regurgitated into the gullet ;
while a muscular fold forms a direct pathway
for the ruminated food to pass at ouce from
the oesophagus to the maniplies.
Pachydennata. The Elephant has a stomach
which is elongated, and subdivided by very
numerous folds. In other respects it is simple.
That of the Rhinoceros is similar ; but the
cardiac pouch is devoid of folds. The shorter
stomach of the Pig is divided internally by two
folds of mucous membrane into three por-
tions : a cardiac pouch, a pyloric extremitj-,
and an intermediate portion, which receives
the cesopliagus. The lesser curvature, and
the back of the cardiac pouch, are both occu-
pied by a white and dense epithelium, which
is similar to that of the oesophagus, and forms
a broad quadrilateral band along this aspect
of the interior. In the Pecari there are ex-
ternal indications of the same subdivisions :
but the white epithelium extends over a
wider surface; so that it is only the pyloric
third, and the lower parts of the middle and
cardiac pouches, which exhibit the proper
gastric or tubular structure. In the Hippopo-
tamus, the stomach is long and tubular, and
is complicated by the addition of two pouches,
which have a size almost equal to its own,
and communicate with its cavity by corre-
sponding orifices on the right of the oesophagus
and at the back of the cardia. The internal
surface of the organ is so folded as to allow
the alimentary bolus to enter either of these
two cavities.*
Tne stomach of the Solipeda has a rounded
shape, and a cardia and pylorus which are close
to each other. The cardiac half of the organ
is lined by a white epidermis, which terminates
by an abrupt dentated margin.
" In all these three orders Ruminants,
Pachyderms, and Solipeds the intestine is
characterized by great length, width, and
convolution, and by the possession of a capa-
cious caecum. Thus, in the Ruminant sheep,
the intestine is thirty times the length of the
body. And although in the Soliped horse this
proportion sinks to fifteen or twenty, still the
* The above is a description of the organ in the
foetal Hippopotamus, to which alone our present
information refers. Cuvier suggests this to have
been an incomplete development of a compound
organ, akin to that of a ruminant : the stomach
being the abomasum, and the diverticula represent-
ing the paunch and honeycomb. But the tough
and wrinkled character of the mucous membrane
which lined the supposed abomasum in the greater
part of its extent seerns to negative this view.
sacculation of the caecum and colon which ob-
tains in this and the Pachydermatous order per-
haps compensates such a diminution in length.
Theilio-caecal valve is represented by a narrow
passage, the mucous membrane of which forms
six or eight thick longitudinal folds. The
caecum, smallest in the Pachyderm, attains its
maximum size in the Soliped ; being, in the
Horse, two feet long, and thrice as capacious
as the stomach. In one Pachyderm the Cape
Hyrax two additional c&ecal tubes open into
the large intestine by wide apertures.
In the Rodentia the stomach is separated
by an external constriction into two portions:
a cardiac, clothed with a thick epidermis,
and a pyloric, occupied by a mucous mem-
brane which has the ordinary tubular struc-
ture. The size of the former pouch varies in
different genera ; the latter sometimes pre-
sents an imperfect subdivision. The whole
organ occasionally approaches a conical or
spherical shape. In the Beaver and Muscar-
din, the stomach is complicated by the addi-
tion of glandular crypts and caeca, the im-
port of which is unknown. The intestine of
the Rodent is very long and convoluted, and
the small and large intestine are of nearly
equal diameter ; but the latter is deeply sac-
culated. The caecum is usually very large,
and is sometimes subdivided by spiral or cir-
cular folds. But in the omnivorous Rat it is
small ; and in the Dormouse it is altogether
absent.
Marsnpialia. In a large proportion of this
order, the stomach has a considerable resem-
blance to that of the human subject. Such
an organ is found in both carnivorous and
herbivorous Marupialia : and indeed, it is
difficult to point out any differences in its
size or shape which are distinctly referrible to
the habits of its possessors. In some, how-
ever, a stomach oF very similar outside shape
exhibits a lesser curvature, which is oc-
cupied by a gastric gland like that of the
Beaver, composed of numerous irregular
crypts. In the Kangaroo (Mao-opus) both the
shape and the structure of the organ differ
widely from the preceding. The stomach is
of a length which equals that of the whole
body ; the cardiac pouch is subdivided into
two caeca ; and the middle part of the organ
is sacculated by three bands of longitudi-
nal muscular fibres, so as closely to resem-
ble the ordinary arrangement of the colon,
except that the interspace between the upper
two, or that third of the surface which occu-
pies the lesser curvature, is not sacculated.
The gastric gland is broken up into numerous
follicles, which are placed in three rows
parallel to the longitudinal muscular bands.
The mucous membrane of the oesophagus
is continued right and left of the cardiac
orifice for a considerable distance; some-
what as in the stomach of the Pig. The re-
mainder of the mucous membrane is of the
ordinary soft character.
The "intestine of the Marsupial is also sub-
ject to great differences. The carnivorous
members of the class are devoid of a caecum.
504
STOMACH AND INTESTINE.
The insectivorous Marsupials have a longer
intestinal canal, which is separated into large
and small intestine, and exhibits a caecum of
moderate size. Those that live upon fruits
have bowels which are still longer, and a
large caecum of twice the length of the whole
body. Finally, the true vegetivorous genera
have a caecum which is thrice as long as the
body. In those which are possessed of a saccu-
lated stomach, the caecum is, however, much
shorter. One genus, the Wombat, has a
vermiform appendix. The length of the whole
intestine varies from two to ten times the
length of the animal.
In the Monotremata the alimentary canal is
chiefly remarkable from its terminating in a
cloaca common to it and the urinary and
generative organs. A small caecum separates
the long and narrow bowel into two parts.
The diameter of the small intestine gradually
diminishes to the caecum, while that of the
large intestine gradually increases to the rec-
tum.
The Cetacea offer two chief varieties of
stomach, which are connected with differences
in their food, though scarcely explained by
them. Those which live on vegetable food
exhibit a simpler form of organ. Thus, in the
Dugong, the stomach is long and transverse ;
and is divided by a deep constriction into a
globular cardiac, and a conical pyloric, portion.
Two large caeca open into it near this con-
striction ; and a special glandular apparatus
occupies the upper part of the cardiac pouch.
In the carnivorous Cetaceans, the stomach is
subdivided into three, five, seven, or more cavi-
ties. In some genera, however, there are only
four. Of these the first has an epidermoid
lining, while the three last have a soft mucous
membrane. The biliary duct often opens into a
dilated cavity, the import of which is unknown.
The intestine is longer in the herbivorous di-
vision. Here there is also a caecum ; which
is sometimes large and glandular, but some-
times small, short, and even bifid. In the
zoophagous Cetaceans there is rarely either
caecum or valve: so that the intestine, which
decreases slightly in size from the pylorus to
the anus, offers no separation into large and
small. But in the genus Batcena there is a
small caecum, like that of the Cat.
The Qnadrnmana possess a stomach the
form of which approaches that of the human
organ. In some cases, however, it is more
elongated ; while in others it assumes a glo-
bular shape, with a cardia and pylorus in close
proximity. The latter deviation is generally
found in conjunction with carnivorous or
insectivorous habits. It is usually separated
into two portions, a cardiac and a pyloric ; and
sometimes the latter, which is more globular
than usual, is distinguished by an internal
fold from a short tubular part, which termi-
nates in the pyloric valve and the duodenum.
Rudimentary pyloric ca3ca have been remarked
by Cuvier * in one instance. The Sem-
nopithecus presents a form of stomach which
* Lemons d'Anat. Comp. vol. iv. p. 28.
recalls that of the Kangaroo. For the cardiac
cavity, smooth and almost bifid at its com-