THE STOMACH. 28/ 



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 unpar- 

 donable 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 seern, 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 existence 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 which a constant gentle 

 motion is communicated to the stomach, mingling the food more intimately 

 together, and preparing it for digestion, and by the pressure of which the food 

 when properly prepared is 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 nume- 

 rous glands on it, which secrete a mucous iluid ; and it is probably intended to 

 be a reservoir in which a portion of the food is retained for a while, and softened 

 and better prepared for the action of the other or true digestive portion of the 

 stomach. The cuticular coat 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 

 digestion properly commences. The mouths of numerous little vessels open 

 upon it, pouring out a peculiar fluid, the gastric (stomach) juice, which mixes 

 with the food already softened, and converts it into a fluid called chyme. As 

 this is formed, it passes out of the other orifice of the stomach, the pylorus 

 ( doorkeepers), /j and enters the first small intestine; the harder and undissolved 

 parts being turned back to undergo farther action. 



Every portion of the muscular coat has the power of successively contracting 

 and relaxing, and thus, in the language of Dr. Bostock, " the successive con- 

 traction of each part of the stomach, by producing a series of folds and wrinkles, 

 serves to agitate the alimentary mass, and, by bringing every part of it in its 

 turn to the surface, to expose it to the influence of the gastric juice, while at the 

 same time the whole of the contents are gradually propelled forwards, from the 

 orifice which is connected with the oesophagus to that by which they are 

 discharged." 



The cerebro-visceral nerve is the agent in producing these alternate con- 

 tractions and relaxations. It is the motor nerve belonging to these parts. It 

 has to keep the parietes of the stomach in contact with the food, and the food in 

 contact with the gastric juice. It has to bring the different parts of the food in 

 successive contact with the stomach, and to propel them through this portion of 

 the alimentary canal in order that they may be discharged into the duodenum. 



