130 SKIN AND ITS APPENDAGES. 



looked after ; it stands, as the faithful sentinel, on the out- 

 posts of the system, giving immediate warning whenever 

 an enemy is at hand, or an injury is suspected, whether 

 by mechanical or chemical violence or the temperature of the 

 atmosphere. This warning is by the sensation of pain. 

 But this function is also intellectual, as, by the sense of 

 touch, it is the medium of knowledge to the mind. ' 



The Secretion of the skin has been stated to be perspira- 

 tory and sebaceous. By this function the properties of 

 smoothness, softness, and pliability are imparted to the 

 skin, and a large amount of superfluous matter thrown 

 off, which, if retained, would destroy life. 



The amount of exhalation from the skin has been esti- 

 mated by Sanctorius. It is stated that for thirty years he 

 daily weighed his body, food, and excretions. His estimate 

 was, that out of every eight pounds of nourishment, five 

 passed off by the skin, leaving only three to be carried off 

 by the lungs, kidneys and bowels. M. Seguin made the 

 amount average about three pounds in the twenty-four 

 hours* Twenty or thirty ounces of this exhalation, it is 

 said, cannot accumulate in the system without causing 

 disease; which is no doubt true. The perspiratory func- 

 tion is also one of refrigeration, as by evaporation the 

 body is cooled. 



Absorption, though at one period denied to the skin, is 

 now fully established as one of its functions; for by the 

 skin many articles of the materia medica are daily intro- 

 duced into the system, and produce their effects with nearly 

 the same certainty as when taken by the mouth. 



The Relations of the skin may be considered as Physical, 

 Chemical, Organic, and Mental. 



The principal physical relation of the skin is atmos- 

 pheric air, of a certain temperature and density. If the 

 temperature be too low, the skin will become cold, torpid, 

 and frozen, while the function of sensation will be ob- 

 scured, benumbed, or entirely lost, and those of secretion 

 and absorption completely checked or destroyed. On the 

 other hand, if the temperature be too high, the violence 



