140 



THE INTEGUMENT 



The dermis projects into the epidermis in the form of ridges and 

 papillae. In the connective tissue near the epidermis are cells con- 

 taining pigment granules and resembling the dermal chromatophores 

 which are so very prominent in the dermis of amphibians. Some 

 of the dermal papilhe contain ca])illary networks furnishing nutri- 

 ment to this region and to the overlying e])idermis. In papillae 

 adjacent to those possessing capillary networks are a number of 

 types of sensory end-organs. 



Sir. corneum 

 Str. gernunativum \;^^i'^^(^ 

 (. " 



Sweat gland 



Subcutisl ■•^/ 





Str. corn rum 

 Str. lucuhilum 

 Str. granulo.sum 

 Str. germinativnm 





> Subcutis 



A B 



Fig. 84. — Diagrams of skin striiftiire. .1, from back of hand; B, from palm of hand. 



Skin of Palm or Sole. — The skin covering the palm of the hand or 

 sole of the foot offers an example of the extreme development of the 

 skin of mammals. (Fig. 84.) The epidermis of these regions ])resents 

 four distinct strata. Proceeding upward from the dermis these are: 

 the stratum germinativnm, the stratmn granulosum, the stratum 

 lucidum, and the stratum corneum, or superficial layer. It is to be 

 understood that cells pass through all these layers before being cast 

 off from the surface of the skin, the ditfercnt layers merely repre- 

 senting various stages in the transformation of the epidermal cell, 

 from the time it leaves the stratum gern.'nativum, until its death 

 and desquamation. 



Stratum Gerininativum. — The lower border of the strat m germi- 

 nativum is not a smooth surface because of the projc^ctioii of dermal 



