334 



ZOOLOGY 



slits become closed as the embryo develops. Above the 

 Amphibia they never bear gills. 



The esophagus is a narrow muscular tube of varying length 



FIG. 162. Stomach of Dog (A) and of Rat (U). c t cardiac portion; p, pyloric portion; o, 



esophagus; *', intestine. 



FIG. 163. 



Pic. 163. Diagram of the stomach of a ruminant, o, esophagus; r, rumen or paunch; re., reticu- 

 him, or honeycomb; p, psalterium or many plies; a, abomasum or rennet; i, intestine. 



Questions on figures 162 and 163. 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? 



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

 (the crop) may serve for the temporary storing and softening of 

 the food. 



