Veterinary practitioners do not seem to have decided, hitherto, whether these animals are prejudicial to the horse ; nor even whether they may not be actually beneficial. Their almost universal exist ence at a certain season, even in ani mals perfectly healthy, shows that they produce no marked ill effect ; yet the boles which they leave, where they were attached to the stomach, could hardly be made without causing some injurious irri tation.
For the mode in which these buttsgain admission into the stomach, as also for a most interesting general account of their history and structure, see (Estrus, which was furnished by Mr. Clark, and from which the preceding account is borrow ed.
The food of carnivorous animals ap proaching in its constituent elements more nearly to those of the animal than that of the herbivorous tribes, is more easily reduced into the state which is re quired for the nourishment of the body in the former than in the latter case. Hence arises a leading distinction be tween the stomachs of these classes. In the latter animals, the esophagus opens considerably to the right of the great ex tremity, so as to leave a large cul de sac on the left side of the stomach ; and the small intestine commences near the car dia, leaving a similar blind bag on the right. The food must be detained long time in such a stomach, as the pass age from the oesophagus to the pylorus is indirect, and highly unfavourable. to speedy transmission. Animals of the mouse kind, and the rodentia, show this structure very well ; it is very remark able in the MAIS quercinus, (Cuvier, "Le cons," 8cc. tom. 5. pl. 36. fig. 11.) In the carnivore, the stomach, which is of a cylindrical form, has no cul de sacs; the oesophagus opens at its anterior extremi ty, and the intestine commences from the posterior ; so that every thing favours a quick passage of the food. Animals of the weasel kind, which are very truly carnivorous, exhibit this structure the most completely. The seal also exem plifies it, and the lion. (Cuvier, pl. 36. fig. 7.) The most complicated and artificial ar rangement, both with respect to struc ture and mechanism, is found in the well-known four stomachs of the rumi nating animals with divided hoofs : of this we shall take, as examples, the cow and sheep.
The first stomach or paunch, (rumen, penula, magnus ventor, ingluvies is by far the largest in the adult animal ; not so however in the recently born calf or lamb. It is divided externally into two saccular appendices at its extremity, and it is slightly separated into four parts on the inside. Its internal coat is beset with innumerable flattened pa pine.
This is followed by the second sto mach, honeycomb bag, bonnet, or king's hood, (reticulum, ollula,) which may be regarded as a globular appendage of the paunch ; but it is distinguished from the latter part by the elegant arrange ment of its internal coat, which forms polygonal and acute-angled cells, or su perficial cavities.
The third stomach, which is the small est, is called the manyplus, which is a ;orruption of manyplies (echinus, con clave, centipellio, omasum): it is distin guished from the two former, both by its form, which has been compared to that of a hedge-hog when rolled up, and by its internal structure. Its cavity is much contracted by numerous and broad du plicatures of the internal coat, which lie lengthwise, vary in breadth in a regular alternate order, and amount to about 40 in the sheep, and 100 in the cow.
The fourth, or the red, (abomasum, fa liscus, ventriculus intestinalis) is next in size to the paunch, of an elongated, pyri form shape, with an internal villous coat like that of the human stomach, with large longitudinal rugm.
The three first stomachs are connected with each other, and with a groove-like continuation of the msophagus, in a very remarkable way. The latter tube enters just where the paunch, the second and third stomachs, approach each other ; it is then continued with the groove, which ends in the third stomach. This groove is therefore open to the first stomachs, which lie to its right and left. But the thick prominent lips which form the mar gin of the groove admit of being drawn together so as to form a complete canal ; which then constitutes a direct continua tion of the oesophagus into the third sto mach.
The functions of this very singular part will vary, according as we consider it in the state of a groove, or of a closed canal. In the first case, the grass, &c. is passed, after a very slight degree of mas tication, into the paunch, as into a reser voir. Thence it goes in small portions into the second stomach, from which, after a further maceration, it is propelled, by a kind of antiperistaltic motion, into the oesophagus, and thus returns into the mouth. It is here ruminated, and again swallowed, when the grobve is shut, and the morsel of food, after this second mas tication, is thereby conducted directly into the third stomach. During the short time which it probably stays in this situation between the folds of the internal coat, it is still further prepar ed fbr digestion, which process is com pleted in the fourth or true digestive stomach.