CHARACTERISTICS OF THE DIGESTIVE APPARATUS. 215 



The stomach is charged to contain the food until it has undergone 

 the chemical modifications which are essential to its absorption. It forms 

 a reservoir -which is in mammals clearly separated from the ossophagus 

 and the intestine, and which, as already stated, occupies a transverse 

 position in mammals, longitudinal in reptiles and the oviparous verte- 

 brates, while its transverse position commences to be indicated in birds. 

 The stomach may be either simple or complex. In carnivora, whose 

 food is easy of solution, it is a single cavity lined with a uniform mucous 

 membrane abundantly supplied with glands which secrete an acid fluid, 

 the gastric juice, which has for its function the conversion of albuminous 



Fig. 73.— Stomach of Different Mammals and of a Tuktle. (Thanhoffer.) 



1, stomach of seal ; 2, stomach of hyena ; 3, stomach of cricetus ; 4. stomach of manate ; 5, stomach 

 of camel ; 6, stomach of sheep ; 7, stomach of lion ; 8, stomach of horse. 



c, cardia ; p, pylorus ; 1, 2, 3, 4, 1st, 2d, 3d, and 4th stomachs ; i\ ventriculus ; /, fundus vcntricuh. 



foods into peptones. The complication of the stomach in mammals 

 progresses in insensible degrees, and in a general way is in proportion to 

 the indigestibility of the food (Fig. 13). At first the division of the 

 stomach into pouches is only indicated by a difference in structure and 

 properties of the mucous membrane of the cardiac and pyloric portions 

 of this viscus. This difference is, to a certain extent, present in all 

 animals, even in the carnivora, where it is confined simply to a histologi- 

 cal difference in the nature of the glands of these two portions of the 

 stomach. No difference is, however, evident to the naked eye in these 

 animals. In the horse the separation into a cardiac and pyloric pouch is 



