COMPARATIVE ANATOMY 



The dermal papilla is thus always the primary part of the 

 scale which causes the elevation of the epiderm (Fig. 18). At 



Horny papilla. 



Malpigltian layer Horny layer 

 Papilla 1 . of eviderm. of epiderm. 



^'VW' 





Derm. 



_ 



Subcutaneous conntrtire 

 tissue with vessels. 



, 



FIG. IS. SECTION OF SKIN OF A YOUNG TORTOISE (Testudo yra'ca), FROM THE 



NECK. 



the same time, a marked proliferation of the epiderm occurs, at 

 first uniformly and later in different degrees on the upper and 

 lower surfaces of scales when they overlap one another (Fig. 19). 



Loose connective Epitrk-hous 

 tissue layer. lai/er. 



Horny layer (scale). 



Piyment In;/' r. 



Muscles. 

 FIG. 19. SECTION OF SKIN OF LIZARD (Laccrla ayi/i*). 



As in Amphibians, a periodic casting of the superficial part of 

 the many-layered horny epiderm occurs, either in shreds, or 



