CHAPTEE IX. 



THE SKIN. 



IT is much easier to under-estimate than to over-estimate the impor- 

 tance of the functions of the human skin as an organ of the body. It is 

 not merely a chance bounding layer of the organism, but truly a living 

 organ as important as any of the viscera. Indeed, few organs have so 

 many functions concerned with so many sorts of essential animal activity 



Again we must refer the reader to the text-books of gross and micro- 

 scopic anatomy, that he may acquire a knowledge of the structure of the 

 skin before he tries to understand its functions. 



FIG. 172 



The functions of the skin. In each of the nine portions of this diagram there is represented 

 those dermal structures chiefly concerned in that function. 



The Functions of the Skin. Among the many uses which the human 

 skin might be said by an ingenious person to have, nine especially may 

 be noted. These are of various degrees of importance to the organism, 

 and only the first four or five are essential to its health. These nine 

 uses of the skin, if we are to denote each of them by some one common 

 expression, are protection, sensation, thermotaxis, excretion of sweat, 

 secretion of sebum, respiration, absorption, coloration, and support of 



