The Skeleton 49 



layer are usually easily isolated in the belly and 

 neck regions where they never become very thick ; 

 but in the back the cells in this layer are very 

 numerous and fuse with each other to form the 

 bony plates ; here the rete is the only clearly differ- 

 entiated layer. Whether prickle cells are present 

 in the epidermis of the crocodile Bronn is not 

 certain, though he thinks they probably are. 



Rathke pointed out that on the surface of cer- 

 tain folds of the integument, especially in the 

 region of the jaws, are found in all Crocodilia 

 certain small, scattered, wart-like elevations, 

 around each of which is customarily a narrow, 

 shallow, circular groove ; they usually have a dark 

 brown but sometimes a gray or even white color. 

 Microscopic examination shows these warts to 

 be of epidermal origin, consisting of bright, round 

 cells that are closely united, without visible inter- 

 cellular substance. Treatment with potassium 

 hydroxid and then with water will show sometimes, 

 though not always, fine granular nuclei in the 

 cells. 



In probably all members of the genus Crocodilus 

 at least is found, on the thick swelling on the right 

 and on the left side of the neck and trunk, a small, 

 flat pit which has the appearance of the opening of 

 an integumental gland. The pits are present also 

 in the scales of the throat, under the side of the 

 neck, sides of the body, lateral and ventral surfaces 

 of the anterior half of the tail, and the legs. They 



