Mil 



PHYLUM CHORDATA 



357 



constitute its food. The tongue in Snakes is slender and bifid, 

 capable of being retracted into a basal sheath, and highly sensi- 

 tive, being used chiefly as a tactile organ. The tongue of the 

 Crocodilia (C) is a thick, immobile mass extending between the 

 rami of the mandible. In some of the Chelonia (B) the tongue is 

 immobile ; in others it is protrusible, sometimes bifid. 



In the enteric canal of the Reptiles the principal special features 

 to be noticed are the muscular gizzard-like stomach of the 

 Crocodilia, the presence of a rudimentary cascum at the junction of 

 small and large intestines in most Lacertilia and in the Ophidia, 



,. i in 1 . i. A, tongue of Monitor indicus. B, tongue of Emys europaea. C, tongue of 

 Alligator. L, glottis ; M, mandible ; Z, tongue ; ZS, tongue -sheath. (From Wiedershehn's 

 Comparative Anatomy.) 



and the presence of numerous large cornified papillaB in the 

 oesophagus of the Turtles. 



Organs of Respiration. The Reptiles all have an elongated 

 trachea, the wall of which is supported by numerous cartilaginous 

 rings. The anterior part of this is dilated to form the larynx, the 

 wall of which is supported by certain special cartilages the cricoid 

 and the arytenoids. The trachea bifurcates posteriorly to form two 

 bronchi, right and left, one passing to each lung. In some of the 

 Chelonia its lumen is divided internally by a vertical septum. 

 The lungs of the Lacertilia and Ophidia are of the simple sac-like 

 character already described in the case of the Lizard. In some the 

 lung is incompletely divided internally into two portions an 

 anterior respiratory part with sacculated walls, and a posterior part 

 with smooth, not highly vascular walls, having mainly the func- 

 tion of a reservoir. The only additional complication to be speci- 

 ally noted is the presence in the Chanueleons (Fig. 1000) of a 



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