EXCRETION. 497 



matter, extractive matter, and stearin; in certain parts, also, it is mixed 

 with a peculiar odorous principle, which contains caproic, butyric, and 

 rutic acids. It is, perhaps, nearly similar in composition to the unctu- 

 ous coating, or vernix caseosa, which is formed on the body of the 

 foetus while in the uterus, and which contains large quantities of 

 ordinary fat. Its purpose seems to be that of keeping the skin moist 

 and supple, and, by its oily nature, of both hindering the evaporation 

 from the surface, and guarding the skin from the effects of the long- 



Fig. 316. Sebaceous gland from human skin. (Klein and Noble Smith.) 



continued action of moisture. But while it thus serves local purposes, 

 its removal from the body entitles it to be reckoned among the excre- 

 tions of the skin. 



CHEMICAL COMPOSITION OF SWEAT. 



Water ...,.-,. , . . . 995 



Solids : 



Organic Acids (formic, acetic, butyric, pro- ) Q 



pionic, caproic, caprylic) $ 



Salts, chiefly sodium chloride . . . .1.8 

 Neutral fats and chplesterin 

 Extractives (including urea), with epithelium 1.6 



1000 



The sweat is a colorless, slightly turbid fluid, alkaline, neutral or 

 acid in reaction, of a saltish taste, and peculiar characteristic odor. 



Of the several substances it contains, however, only the carbonic acid 

 and water need particular consideration. 



Watery Vapor. The quantity 6*f watery vapor excreted from the 

 3* 



