322 



METAZOAN PHYLA 



The pharynx in the lower vertebrates is respiratory in function, since 

 in its walls lie the gill slits. In the higher forms it serves as a common 

 passageway for the food from the mouth into the esophagus and for the 

 air from the nasal chamber into the windpipe, or trachea. 



Nasa/ 

 chamber 



Tongue 



Larynx 

 Trachea 



Soff- pcf/ahe 



— Pharynx 

 Esophagus 



Liver 



Gall 

 bladder 



Pyloric 

 Opening 



Transi/erse 

 colon 



/iscenpfinq- 

 colon 



Lung 



Cardiac 

 opening 



Diaphragm 

 Spleen 



Descending 

 colon 



Appendix 



^RecTurn 



Fig. 215. — Alimentary canal of man. {From Sobotta, " Deskriptivc Anatomie," by the 



courtesy of J . F . Lchmann's Verlag.) 



The esophagus may be simply a passageway for food on its way to the 

 stomach, or as in the case of many birds, it may be dilated to form a 

 crop for the storage of food. 



The stomach is an organ in which the food is reduced to liquid form 

 and in which a certain amount of digestion takes place. In the walls of 

 the stomach are glands which secrete pepsin and rennin and also hydro- 

 chloric acid, giving to the contents an acid reaction. The rennin, in this 

 acid medium, serves to coagulate the protein of milk, separating it as the 



