242 



COMPARATIVE MORPHOLOGY OF VERTEBRATES 



position, or it may be divided into chambers, reaching the extreme 

 in this respect in the ruminants (fig. 255) and the cetacea (fig. 

 254, E) where four compartments are recognized. In the ruminants 

 two of these, the rumen or paunch and the reticultun or honeycomb, 

 are expansions of the oesophagus and serve as reservoirs for food. 

 When feeding the herbage is swallowed and passes into these. Then 

 it is regurgitated into the mouth for mastication, and when it is 

 swallowed again it passes at once into the other parts of the stomach, 

 following the course of the dotted lines of figure 255 to the psalte- 

 riimi (omasus ormanyplies), and the abomasum or rennet for gastric 

 digestion). . 



Fig. 255. — Diagram of ruminant stomach, the dotted line showing the course of the 

 food, a, abomasum; oe, oesophagus; />, pylorus; ps, psalterium (omasus, manyplies); 

 rt, reticulum (honeycomb); ru, rumen (paunch). 



INTESTINE 



The remainder of the prehepatic portion of the alimentary canal, 

 extending from the pylorus to the entrance of the bile duct, is con- 

 sidered as part of the intestine, this region, together with the first 

 part of the posthepatic tube being called the duodenimi. It is espe- 





Fig. 256. — Digestive tube of garpike, Lepidosteus (after Gegenbaur). i, small intestine; 

 oe, oesophagus; pc, pyloric caeca; pg, pylorus; r, rectum; s, stomach; sv, spiral valve. 



cially noticeable in many ganoids and teleosts (figs. 256, 259) where it 

 may bear from one to two hundred blind digestive tubes, the pyloric 

 caeca. The same region in a few elasmobranchs may have a pair of 

 these caeca or (Galeus) it may be expanded into a pouch ('bursa 

 Entiana*). 



