222 THE ABDOMEN AND ITS CONTENTS. 



\ microscope of very feeble power will beautifully show this singular coriatr action 



It is not precisely either a sphincter muscle 

 or a valve, but it is a strong and almost 

 insuperable obstacle to the regurgitation of 

 the food. The left side of the stomach is 

 in contact with the diaphragm. It is piessed 

 upon by every motion of the diaphragm, 

 and hence the reason why the stomach ia 

 so small compared with the size of the 

 animal. It is indeed strangely small, in 

 order that it might not press too hardly 

 upon the diaphragm, or painfully interfere 

 with the process of respiration, when the 

 utmost energies of the horse are occasion- 

 ally taxed immediately after he has been 



At the lower or pyloric orifice, the mus- 

 iles are also increased in number and in size. These are arranged in the same 

 manner, with sufficient power to resist the pressure of the diaphragm, and retain the 

 contents of the stomach until they have undergone the digestive process. 



The situation of the stomach will at once explain the reason why a horse is so 

 much distressed, and sometimes irreparably injured, if worked hard immediately after 

 a full meal. The stomach must be displaced and driven back by every contraction 

 of the diaphragm or act of inspiration ; and in proportion to the fulness of the stomach 

 will be the weight to be overcome, and the labour of the diaphragm, and the exhaus- 

 tion of the animal. If the stomach is much distended, it may be too weighty to be 

 forced sufficiently far back to make room for the quantity of air which the animal in a 

 state of exertion requires. Hence the frequency and labour of the breathing, and the 

 quickness with which such a horse is blown, or possibly destroyed. Hence also the 

 folly of giving too full a meal, or too much water, before the horse starts on a journey 

 or for the chase ; and, in like manner, the absurdity and danger of that unpardonable 

 custom of some grooms to gallop the horse after his drink, in order to warm it in his 

 belly, and prevent gripes. 



The horse was destined to be the servant of man, and to be always at his call 

 whether fasting or full : it would seem, therefore, that, to lessen much inconvenience 

 or danger, a smaller stomach, in proportion to his size, is given to the horse than to 

 almost any other animal. The bulk of the horse, and the services required of him, 

 demand much nutriment, and that of such a nature as to occupy a very considerable 

 space ; yet his stomach, compared with his bulk, is not half so large as that of the 

 human being : therefore, although he, like every other animal, feels inconvenience 

 from great exertion immediately after a full meal, he suffers not so much as other 

 quadrupeds, for his stomach is small, and his food passes rapidly through it, and 

 descends to a part of the intestines distant from the diaphragm, and where the exist- 

 ence and pressure of the food cannot cause him any annoyance. 



The stomach has four coats. The outermost is the lining of the cavity of the belly, 

 and the common covering of all the intestines that by which they are confined in 

 their respective situations, and from which a fluid is secreted that prevents all friction 

 between them. This is called the peritoneum that which stretches round the inside 

 of the stomach, 



The second is the muscular coat, consisting of two layers of fibres, one running 

 lengthways, and the other circularly, and by means of w r hich a constant gentle motion 

 s communicated to the stomach, mingling the food more intimately together, md pre- 

 o&ring it for digestion, and by the pressure of which the food when properly prepared 

 in urged on into the intestines. 



The third, or cuticular (skin-like") coat, c, covers but a portion of the inside of the 

 stomach It is a continuation of the lining of the gullet. There are numerous glands 

 on it, which secrete a mucous fluid ; and it is probably intended to be a reservoir in 

 which a portion of the food is retained for a while, and softened and bettei prepared 

 for the action of the other or true digestive portion of* the stomach. The cuticula? 

 ftoat occupies nearly one-half of the inside of the stomach. 



The fourth coat is the mucous or villous (velvet) coat. e. where the work of dijrestio* 



