OF THE HAIRS. 233 



substance, which loses a portion of the elasticity and tenacity 

 of the hair, has all the properties of coagulated albumen. They 

 strongly resist putrefaction. Their colour changes at first, but 

 the corneous matter resists for a great length of time. Vau- 

 quelin has found that they dissolve in Papin's digester; that 

 they are dissolved by water containing four hundredths of 

 caustic potash; and that they are acted on by all the acids. 

 According to this celebrated chemist, they are composed of 

 an animal matter which forms their base, of a small quantity 

 of a white concrete oil, of a blackish oil, of iron, oxide of man- 

 ganese, phosphate of lime, carbonate of lime, silex and sul- 

 phur. 



341. They are neither irritable nor sensible; their force of 

 formation or vegetative power is very active. 



The motions of the hairs are communicated to them by the 

 sub-cutaneous muscles, and by the contraction of the skin itself. 

 Each of the large hairs or prickles of certain animals, are, in 

 addition, provided at the root with a little muscle destined to 

 elevate it. Although, strictly speaking, the stems of the hairs 

 are insensible, yet as their roots are placed over a papilla pro- 

 vided with a nerve, they transmit to it with great accuracy 

 the effects of contact with external bodies that act on them 

 mechanically. Their production or vegetation is continual, it 

 is analogous to that of the epidermis and the nails, and like it, 

 constitutes a true excretion. Certain facts seem to indicate, 

 that there occurs in their interior, not a true circulation, but an 

 imbibition, and that a coloured liquid slowly traverses them, 

 from the root towards the summit. They have been stated, 

 without any proof, to be organs of absorption. Their use is to 

 protect the skin, and in some places, particularly, to serve the 

 purposes of sensation. They have also local uses. 



342. The hairs present considerable differences, relative 



to the regions they occupy, and have received various names. 



On the cranium they are called, hair, capilli, coma, ctesa* 



ries: these hairs are the longest, the most numerous, strongest 



and thickly set. 



The brows and lashes belong to the eyes; the orifices of the 

 nostrils and ears are also furnished with hairs. 



