The division of the stomach into distinct cavities is most remarkable in the ruminantia. All these animals have four stomachs, differing in structure and appear ance, so that tney have been distinguished by particular names. The hest of tlitse, and the largest in the adult animal, is the paunch. This is divided externally into two portions, and on its central surface, where it is be set with numerous flattened papilla, there is an obscure division into four parts. The second stomach is much smaller than the former, to which it might be considered as an appendage, but for the very different appearance of its central surface. Tnis is marked with numerous shallow cavities or cells, of an angular figure, resem bling the cells of a honey-comb, whence this stomach is sometimes called the honey-comb bag, though it is better known by the name of the king's hood. Next to this is the smallest of the four cavities called the many plies, from the numerous broad doublings of its central membrane. The last portion is the abomasum or red, which is of an oblong, conical figure, not much inferior in size to the paunch, and marked within with several longitudinal furrows.
The first three of these divisions are connected with each other, and with the gullet in a remarkable manner. The gullet enters just where the paunch, and the second and third stomachs approach each other, and is conti nued to the third stomach by a peculiar groove, with thick prominent lips, which admit of being drawn toge ther, so as to form a perfect tube. Thus, when these lips are closed, there is a communication only between the gullet and third stomach, while in the ordinary re laxed state of the groove, the gullet communicates with the first and second, as well as with the third sto mach.* The effect which this structure has in that peculiar modification of the digestive process called rumination, will be explained under I\ IiimmALIA.
The stomachs of mammalia are in general rather membranous than muscular, but there are a few instan ces in which they approach that remarkable muscula rity which we shall immediately describe in the class of birds. The stomach of the pangolin (mania pentadac tyla) and that of the orni‘horynchus, has its sides ex ceedingly strong and fleshy, while the cavity is propor tionally small, and is generally found to contain sand or gravel, like the gizzard of fowls.
The stomach of the CETACEA, like that of the rumi nantia among quadrupeds, consists of several distinct cavities. Of these there are generally four, though in some instances five, of which the first two are usually the largest, and the third the smallest. Their internal structure resembles that described in the rundnantia.
In BIRDS, the stomach is commonly situated at the dorsal side of the abdomen, and appears to rest on the bowels. In the cuckoo, the ramjzhastos, and the nut cracker, however, it is more sternad. The structure of
this cavity, like that of the stomachs of quadrupeds, dif fers according to the nature of the food which it is to receive. In most of those birds that feed on flesh and insects, the stomach is a membranous bag, while in those birds that are granivorous, this organ consists of two fleshy hemispheres of great strength and thickness, with two smaller fleshy appendages, and a very strong, thick, callous lining. This stomach is well known by the name of gizzard, and the strength of its muscular sides and central lining is so remarkable as to enable it to break in pieces very hard bodies, and to wear off, without any apparent injury, their sharpest prominen ces. See There is little remarkable in the stomach of REP TILES and SERPENTS. In some of the•former, as in the crocodile, this organ, in the thickness of its coats, and proximity of its apertures, resembles the gizzard of fowls. In serpents, the stomach is usually very small.
In most FISHES, the stomach is small, and its coats thin and membranous ; but in some tribes and species, the sides of the stomach are strong and muscular, and its internal membrane callous, bearing a distant resem blance to the gizzard of gallinaceous birds.
The stomach of the MoLLuse.A. is generally membra nous, but in some instances, as in the genus onchidion and the helix stagnalis, it is muscular resembling a giz zard. The aplysice have three muscular stomachs, fur nished with a pyramidal bony processes.
The stomach of many of the CRUSTACEA is extreme ly curious. Thus, in the crab and lobster, there is a bony apparatus surrounding the cavity of the stomach, so as to prevent it from collapsing ; and within the mem branous bag that forms the stomach, round that aperture which is analogous to the pylorus, are fixed those den ticulated bodies which are called teeth in these animals. Both these teeth and the peripheral bony apparatus, are set in motion by strong muscles, and thus the shells that inclose the prey of these animals, are broken in pieces.
In Insects the stomach is commonly simple and mem branous, but in a few instances, as in some of the grylli, it consists of several portions ; and in the ear-wig (for ficida auricularia) it is furnished with two rows of teeth next the gullet.
In those ZOOPHYTES which are called polypes, the whole animal may be said to consist of stomach, as it is chiefly composed of a membranots tube for receiving and dissolving its food ; furnished with tentacula round its only orifice, for seizing and detaining it.
In all animals, except the zoophytes, there is an intes tinal canal distinct from the stomach, though in some classes and tribes, this distinct tube is very short and simple. It is most remarkable in the \IAmmALIA, CE