ZOOLOGY. 
, “ In the heron (ardea cinerea) they are in the same situa¬ 
tion as in the solan goose; they are thinly scattered, and do 
not form a complete belt, being more numerous on the ante¬ 
rior and posterior surfaces. A ball of fish-bones, held toge¬ 
ther by mucus, was found in the cavity of the gizzard. 
“In the cormorant (pelecanus carbo) the situation of the 
solvent glands is the same as in the solan goose; but they 
only form two circular spots, one anterior, the other pos¬ 
terior. 
“ In birds that live upon fish- and sea insects with crusta- 
ceous coverings, as the sea-gull (larus canus), the gizzard 
has a horny cuticular lining, and the solvent glands are in 
the same situation as in the genus falco. 
“ In those birds that live on land insects, some of whose 
coverings are soft, others hard, there is a difference in the 
structure of the digestive organs from what has been de¬ 
scribed. The solvent glands are placed in a triangular form 
in the cardiac cavity, and immediately under it is a small 
gizzard with a horny lining. Of this kind is the wood¬ 
pecker (picus minor). 
“ There is still another variety in the structure of these 
organs. In the little auk (ffie alca alle) the solvent glands 
are spread over a greater extent of surface than in any other 
bird that lives on animal food, and the form of the digestive 
organs is peculiar to itself. The cardiac cavity appears to 
be a direct continuation of the oesophagus, distinguished from 
it by the termination of the cuticular lining, and the appear¬ 
ance of the solvent glands. The cavity is continued down 
with very gradual enlargement below the liver, and is then 
bent up to the right side, and terminates in a gizzard ; when 
the cavity is laid open, the solvent glands are seen at its 
upper part, every where surrounding it, but lower down they 
lie principally upon the posterior surface, and where it is 
bent upwards, towards the right side, they are entirely want¬ 
ing. The gizzard has a portion of its anterior and posterior 
surfaces opposite each other, covered with horny cuticle. 
“ In birds that live principally on vegetable food, the sol¬ 
vent glands have a different structure, according to the sub¬ 
stances the birds are intended to feed upon, and vary in situ¬ 
ation according to the habits of life.” 
These facts are illustrated by the annexed figures; fig. 12 
shews the gizzard of the swan, laid open to expose the in¬ 
ternal structure. The grinding surfaces have an oval form, 
and each of them is made up of a ridge and hollow, which 
are adapted to the opposite side, the ridge of one fitting into 
the hollow of the other. Reduced to one fourth of the natural 
size. 
Of the alimentary canal in the Mammalia .—The sali¬ 
vary glands of the mammalia exhibit very few variations in 
structure. They are small in the carnivora, as mastication, 
properly so called, can hardly be said to take place in them. 
On the contrary, the ruminantia and solipeda have them very 
large. The size of the sub-maxillary gland, in particular, is 
remarkable in the cow and sheep: it extends along the side 
of the larynx, quite to the back of the pharynx. 
The parotid and sublingual glands do not exist in the 
amphibious mammalia, as the seal : the teeth of that animal 
are only adapted for seizing their prey, and must be utterly 
incapable of mastication. The same remark may be made 
on the cetacea, where the salivary system seems to be altoge¬ 
ther deficient. 
The mucous glands, which constitute the labiales and 
buccales of man, are larger and more distinct in some animals. 
There is a row of these opposite to the molar teeth of the dog 
and cat, penetrating the membrane of the mouth by several 
small openings. There is also a considerable gland in the 
dog, under the zygoma, and covered by the masseter. Its 
duct, equal in size to that of the parotid, or sub-maxillary 
glands, opens at the posterior extremity of the alveolar mar¬ 
gin of the upper jaw. The molar glands and their openings 
are very conspicuous in the pig; The cow and sheep have 
an assemblage of similar glands in the zygomatic fossa: their 
excretory ducts open.behind the last superior molar tooth. 
No mammalia possess an uvula, except man and the simise. 
Vol. XXIV. No. 1676. 
S33 
As the cetacea possess no nostrils, they have not of course any 
velum palath 
The parts about the pharynx in the cetacea exhibit a very 
singular structure. The larynx is elongated, so as to form a 
pyramidal projection, on the apex of which its opening is 
found. The projection of this part will divide the pharynx; 
and the food must pass on either side of the pyramid. A 
muscular canal extends from the pharynx to the blowing 
holes, and is attached to the margin of those apertures. The 
circular fibres of this tube form a sphincter muscle; which, 
by contracting round the pyramid, cuts off the communica¬ 
tion between the blowing holes and the mouth and pharynx. 
The oesophagus of quadrupeds is distinguished from that 
of the human subject by possessing two rows of muscular 
fibres, which pursue a spiral course and decussate each other. 
In those carnivorous animals which swallow voraciously, as 
the wolf, it is very large ; on the contrary, in many of the 
larger herbivora, and particularly in such as ruminate, its 
coats are proportionally stronger. 
The opening of the oesophagus into the stomach is marked 
by some differences, both with regard to its size, and to the 
mode of termination. We understand, from observing these 
points, why some animals, as the dog, vomit very easily, 
while others, as the horse, are scarcely susceptible of this 
process, except in extremely rare instances. 
It seems extraordinary, on the first consideration, that the 
ruminating animals, in whom the passage of the food from 
the first stomach into the oesophagus is very easy, should not 
be excited to vomit without such difficulty. 
The form, structure, and functions of the stomach, are 
subject to great variety in this class of animals. In most 
carnivorous quadrupeds, particularly those of a rapacious 
nature, it bears a considerable resemblance, on the whole, to 
that of the human subject; its form, however, differs in some 
cases, as in the seal (phoca vitulina), where the oesophagus 
enters directly at the left extremity, so that there is no blind 
sac formed in the stomach. 
The truly carnivorous stomach, as well as the human, 
which in its structure is closely allied to it, is, according to 
Sir E. Home, capable of dividing its cavity into two distinct 
portions by a transverse contraction of its coats, in which 
state the cardiac portion is, in length, two thirds of the whole, 
but, in capacity, much greater, and in several instances, 
where the opportunity was afforded of examining the part 
immediately after death, the stomach has been found in this 
form both in the human body and other animals. This ap¬ 
pearance corresponds with the permanent form of the stomach 
of many other animals. 
In some herbivora the stomach has an uniform appear¬ 
ance externally; but it is divided into two portions inter¬ 
nally, either by a remarkable difference in the two halves of 
its internal coat, as in the horse, or by a valvular elongation 
of this membrane, as in several animals of the mouse, kind. 
This is also the case in the hare and rabbit, where also the 
food in the two halves of the stomach differs very much in 
appearance, particularly if the animal has been fed about two 
hours before death. 
The reader may refer to the plates, where fig. 13 indicates 
a hare’s stomach that has the appearance before described; a, 
the oesophagus; b b, the cardiac portion of the stomach ; d, 
the pyloric ; c, a muscular band separating them; e, gastric 
glands; f pylorus; g, duodenum. 
In the animals alluded to in this paragraph the left half of 
the stomach is covered with cuticle, while the other portion 
has the usual villous and secreting surface. The cuticular 
covering forms a more or less prominent ridge at its termina¬ 
tion. The left portion of the cavity may be regarded as a 
reservoir, from which the food is transmitted to the true di¬ 
gestive organ ; and the different states in which the food is 
found in the two parts of the cavity justify the supposition. 
Hence these stomachs form a connecting link between those 
of ruminating animals on one side, and such as have the whole 
surface villous on the other. 
In some other mammalia, particularly the herbivorous ones, 
9 A this 
