198 



STRUCTURE OF THE VERTEBRATES 



with diet, the Eskimos having a shorter intestine than the white 

 races. 



1. IMouTH AND Pharynx. In the fish and primitive amphibia 

 the mouth cavity and the pharynx are continuous, the Latter 

 being the larger of the two regions. With the disappearance of 



Gill slits, 



Eicstachian 

 me 



Mouth 



^^^^^^ Heart 



Fig. A Dogfish 



Eustachian 

 tube 



Mouth'", 



Fig. C 



Mouth 

 cavity 



Alligator 



Esophagus 



Fig. 113. Comparative Anatomy of the Mouth Cavity and Phar3'nx. In 

 the Dogfish the cavity of the mouth and pharynx is continuous. A slight 

 separation occurs in the lizard, and in the alligator folds of tissue 



separate the two. 



the gill slits in the adult, which occurs in the more specialized 

 amphibia and all the amniotes, the pharynx tends to be relatively 

 smaller, and in the higher amniotes is separated from the mouth 

 by a fold of tissue. In the mammals this is the soft palate. 

 The mouth is distinguished by the jaws with teeth. In the fish 



