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 
4 
