CHARACTERISTICS OF THE DIGESTIVE APPARATUS. 217 



extremity, or the rudiment of the gizzard, membranous, while in the horse 

 the reverse holds. In the hog (Fig. 75) the division into pouches is 

 more marked by the appearance of a distinct, curved, conical diverticulum 

 at the cardiac extremity of the stomach. In the porcupine three or four 

 contractions are marked, and in the kangaroo, porpoise and other ceta- 

 ceans, and many rodents a large number of dilatations, separated by 

 marked constrictions, are to be noticed (Fig. 76). In other animals this 

 complication is not only in external form, but also in internal structure, 

 the highest degree of complexity being found in the ruminant, where 

 the stomach, so called, is divided into four distinct gastric sacs, com- 

 municating with each other only by small orifices, whose function and 

 structure will occupy us later (Fig. 77). This complication is found not 



Fig. 76.— Stomach of the Dugong, after Sir Everard Home. 



A cardiac portion of stomach ; B, pyloric portion ; C. constriction between the two ; D D, tubular prolongations 

 of the stomach ; F, cesophagus ; G, intestine. 



only in mammals, but also in birds ; but, whatever may be the external 

 form of the organ, the function is always the same,— to supply an acid 

 secretion for the solution and digestion of certain constituents of the 

 food,— and where reservoirs are present their function is simply to 

 retain food until, as in the case of the ruminant, it may be again masti- 

 cated ; or in all eases to enable the food to undergo preparatory changes 

 before being subjected to the action of the gastric secretion. 



The intestine is the prolongation of the stomach, and its shape as a 

 canal is again regained. In its simplest form in the lowest animals it is 

 a short tube of uniform size, with the same structure and properties from 

 one end to the other, as seen in invertebrates, in most reptiles and fishes, 

 and, among the mammals, in the hedgehog and the bat. In the higher 



