332 



ZOOLOGY. 

 FIG. 161. 



FIG. 161. Diagram of the stomach of a ruminant, o, oesophagus; r, rumen or paunch; 

 re., reticulum, or honeycomb; p, psalterium or many plies; a, abomasum or rennet; 

 i, intestine. 



Questions on Figs. 160 and 161. Taken as a series, what is illustrated 

 by the three diagrams? What do the arrows indicate? What is known 

 of the function of the various portions of the ruminant stomach? 



as the part of the digestive tract in connection with which the 

 lungs or gills are developed. In fishes and in the embryos of 

 higher forms 'there are slits in the side walls connecting the 

 pharynx with the outside. Gills are developed in the walls 

 of these slits. In forms above fishes the slits become closed as 

 the embryo develops. Above the Amphibia they never bear 

 gills. 



The oesophagus is a narrow muscular tube of varying length 

 leading to the stomach. In birds an enlarged portion of it 

 (the crop} may serve for the temporary storing and softening 

 of the food. 



The stomach is usually well differentiated and may consist 

 of one chamber or of several. In the latter case there is a 

 division of labor among the parts. One portion may be highly 

 muscular and supplied with a hardened internal lining for 

 grinding the food (gizzard of fowls, Fig. 162) ; in such in- 

 stances another portion is glandular. In the ruminants (ox. 



