250 DIGESTIVE SYSTEM. 



creased pressure must counteract its efforts to recede, and the 

 thorax, under these circumstances, must have recourse to other 

 inspiratory agents — the intercostal muscles, and those passing 

 from the ribs to the fore extremities. This accounts for the in- 

 aptitude of horses recently fed to undergo violent exertion, and 

 the increased embarrassment in respiration that hard work then 

 occasions — why they should be sooner blown, and why they will, 

 if pressed, absolutely sink from premature exhaustion : hence the 

 practice of keeping hunters short of water, and of feeding them 

 unusually early, and on corn only, on the morning of hunting. 



Form. — The stomach has been not inaptly likened to the air- 

 bag of a set of bag-pipes : I should probably fail in conveying so 

 good an idea of its shape by any other resemblance. 



Division. — For the convenience of description, it has been 

 divided into several parts : e. g. an upper and an under surf ace ; 

 a left or large extremity, which is fornjed into a large blind 

 pouch or cul-de-sac, called its fundus ; and a right or small end, 

 which opens with a bend into the duodenum or first intestine ; a 

 large curvature, to which the spleen is attached ; and a small 

 one, extending between its two openings : the former of these 

 curvatures, in the living animal, is turned upwards and back- 

 wards ; the latter, downwards and forwards. 



Orijices. — The stomach has two orifces. One, in which the 

 esophagus terminates, is situated about the centre of its anterior 

 part, at the right extremity of the small curvature, and takes the 

 name of cardia : it is constantly closed but when matters are 

 passing into or out of the organ. The otlier is placed at the ter- 

 mination of the right or small extremity, and opens into the 

 duodenum : though it has the power of closing, this one is mostly 

 open. 



Connexion. — The stomach is fastened in its place by its union 

 with the esophagus and duodenum. It has other connexions, 

 but they are of a peritoneal nature : viz. at its great curvature, it 

 is attached to the spleen and colon by the omentum, at the cardia 

 to the diaphragm by a fold of peritoneum, and near its pyloric 

 end to the liver by an extension of the same membrane. The 

 esophagus, previously to entering the stomach, makes a sudden 

 incurvation downward, by which an angle of such a nature is 

 formed between them at their junction as to have the effect of a 

 valve in preventing any regurgitation of aliment. 



Volume. — Perhaps no animal, in proportion to its size, has so 

 small a stomach as the horse. Let us only compare it with that 

 of the human subject: the stomach of a middle-sized man (a 

 man weighing twelve stone) will contain more than three quarts 

 of water; whereas that of an ordinary-sized horse, whose body 



