PROTECTIVE PUXCTION OF THE SKIN. 



409 



sects. But this part of the subject is too lar^ for detailed 

 treatment in such a work as this. Turning to the vertebrates, 

 we see scales, bony plates, feathers, spines, hair, etc., most of 

 them to be regarded as modifications of the epidermis, always 

 useful, and frequently also ornamental. 



Primitive man was probably much more hirsute than his 

 modern representative ; and, though the human subject is at 

 present provided with a skin in which protective functions are 

 at their lowest, still the epidermis does serve such a purpose, as 



all have some time realized when 

 it has been accidentally removed 

 by blistering, etc. 



Taking the structure of the 

 skin of man as representing that 

 of mammals generally, certain 

 points claim attention from the 

 physiologist. Its elasticity, the 

 failure of which in old age ac- 

 counts for wrinkles; its epider- 



Fis. 311. 



Fig, 312. 



FiH. 811.— Sadoriparous glands. 1x30. (After Sappey.) 1, 1, epidermis; 2, 2, mncons 

 layer; 3, 3, papilte: 4, 4, derma; 5, 5, subcutaneoas areola tissue; 6. G, 6, 6, sudo- 

 riparous glands; 7 7, adipose vesicles; 8, 8, excretory ducts in derma; 9, 9, excre- 

 tory ducts divided. 



Fio. 31S.— Portion of skin of palm Of hand about one-half an inch (127 mm.) square. 

 1x4. (After Sappey.) 1, 1, 1, 1, openings of sudoriferous ducts; 2, 2, 2, 8, grooves 

 .between papilla: of skin. 



mal covering, made up of numerous layers of cells; its coiled 

 and spirally twisted sudoriferous glands, permitting of move- 

 ments of the skin without harm to these structures; its hair- 

 follicles and associated sebaceous glands, the fatty secretion of 

 which keeps the hair and the skin generally soft and pliable. 



