CHAPTER XXYI. 



SKIN, HAIR, AND NAILS. 

 BY ALFRED BIESIADECKI, 



PROFESSOR IN CRACOW. 

 A. SKIN. 



THE skin (integumentum commune) constitutes an invest- 

 ment or covering to the entire surface of the body, and 

 serves to protect it from external injury, though it performs 

 many other and not less important purposes. In order to 

 fulfil these objects, it is provided with various glandular, horny, 

 and nervous structures that are not equably distributed over 

 its whole extent, but are accumulated in particular regions. 

 It thus becomes necessary to distinguish between the essential 

 constituents of the skin, or those that are everywhere present, 

 and those that are peculiar to special regions or districts. 



To the former series belong the true skin, or corium, with 

 its epidermic covering, and the subcutaneous connective tissue, 

 or tela subcutanea ; to the latter, the various horny structures, 

 the hair and nails, the glands, and the terminal organs of the 

 nerves, all of which require separate consideration. 



The integumentum commune is composed of the cutis and 

 the subcutaneous connective tissue, and the cutis again is sub- 

 divided into the dermis, or corium, and the epidermis. The 

 dermis, or corium, is the most essential part of the skin, and 

 forms a dense, but little elastic, white and opaque membrane 

 composed of connective tissue. Its inner surface is continuous, 

 without any sharp line of demarcation, with the subcutaneous 



