THE SWEAT. 433 



^for their products cannot be separated) consists of cast-off 

 epithelium-cells, with nuclei and granules, together with 

 an oily matter, extractive matter, and stearin ; in certain 

 parts, also, it is mixed with a peculiar odorous principle, 

 which is said by Dr. Fischer to contain caproic, butyric, 

 and rutic acids. It is, perhaps, nearly similar in composi- 

 tion to the unctuous coating, or vernix caseosa, which is 

 formed on the body of the foetus while in the uterus, and 

 which contains large quantities both of olein and margarin 

 (J. Davy). 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-continued action of 

 moisture. But while it thus serves local purposes, its 

 removal from the body entitles it to be reckoned among 

 the excretions of the skin; though the share it has in the 

 purifying of the blood cannot be discerned. 



The fluid secreted by the sudoriparous glands is usually 

 formed so gradually, that the watery portion of it escapes 

 by evaporation as fast as it reaches the surface. But, 

 during strong exercise, exposure to great external warmth, 

 in some diseases, and when evaporation is prevented by the 

 application of oiled silk or plaster, the secretion becomes 

 more sensible and collects on the skin in the form of drops 

 of fluid. A good analysis of the secretion of these glands, 

 unmixed with other fluids secreted from the skin, can 

 scarcely be made ; for the quantity that can be collected 

 pure is very small. Krause in a few drops from the palm 

 of the hand, found an acid reaction, oily matter, and mar- 

 garin, with water. 



The perspiration of the skin, as the term is sometimes 

 employed in physiology, includes all that portion of the 

 secretions and exudations from the skin which passes off by 

 evaporation ; the sweat includes that which may be collected 

 only in drops of fluid on the surface of the skin. The two 

 terms are, however, most often used synonymously ; and 



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