CHEMICAL COMPOSITION OF THE HAIRS. 445 



by the bulbs, and varying consequently in its properties in 

 different individuals. It is to a change in the color of this oily 

 matter, arising from a variety of causes, which enfeeble' the 

 general system, as grief, intense study, &c., that is attributed the 

 whitening of the hair. 



The SKIN, constructed as above described, answers a fourfold purpose in the 

 animal economy. It is the organ of touch. It covers and protects the whole 

 structure. It is the outlet for a large proportion of the insensible perspira- 

 tion, and it performs to a certain extent absorption. 



Many facts have been noticed by practitioners of medicine, which proves that 

 it has a connexion with the lungs and stomach, which is not yet explained by 

 anatomy. 



As one of these, an effect of the urticaria or nettle-rash may be mentioned. 

 This eruption sometimes relieves completely the spasmodic croup; and in 

 other cases, nausea and vomiting. 



Some children, when affected with this species of croup, are relieved by rubbing 

 the skin with harsh woolen cloth. 



In some places, the urticaria and the affection of respiration are so much 

 regarded as symptoms of the same disease, that the term hives is used as the 

 name for each of them. 



38 



