OUTLINE OF THE STRUCTURE OF THE HORSE. 61 



arrange themselves into segments of circles, interlacing each 

 other, and, by their contraction, plainly and forcibly closing 

 the opening, so that regurgitation of the food (vomiting) is 

 almost impossible." 



The other opening is that which communicates with the 

 intestines. It is called the pylorus, (literally, door-keepers,) 

 or pyloric orifice. In the cut it is imperfectly represented at /. 

 We quote again from Youatt : "At the lower, or pyloric 

 orifice, the muscles are also increased in number and in size. 

 These are arranged in the same manner (as around the car- 

 diac orifice), with sufficient power to resist the pressure of 

 the diaphragm, and retain the contents of the stomach until 

 they have undergone the digestive process." 



Similar names have been given the two sacs — the cardiac 

 and pyloric. The division of the stomach into these two 

 parts is not uniformly marked in difterent horses, biit is gen- 

 erally indicated, more or less plainly, by a constriction. It 

 is shown in the cut by d d, the jagged and heavily shaded 

 line between c c and e e. The cardiac sac is simply a reser- 

 voir of the food, while the pyloric is the real digestive 

 stomach. 



The stomach is composed of three coatings. The outer 

 coat is a serous membrane, and simply a continuation of the 

 peritoneum, which lines the entire abdominal cavity. Next 

 to this is the muscular, or middle coating, consistiig of two 

 sets of fibers crossing each other transversely, which give to 

 it a considerable power of contraction and expansion. By 

 this means a gentle vibratory motion is imparted to the stom- 

 ach, and all its contents are properly mingled together and 

 carried forward. The internal coating is not the same in the 

 two sacs of the stomach. In the cardiac sac it is commonly 

 called the ciiticular (skin-like), or insensible coating (see c c in 

 cut); in the pyloric, tbe mucous or villous (velvet) coating 

 (see ee in cut). 



The cuticular lining is a continuation of that of the oeso- 

 phagus. It is whitish brown in color, tough, and compara- 

 tively dry. It covers only about one-third of the internal 



v\t 



