348 INTEGUMENTS. 



they soon put forth another crop of hair. The rudiments of the 

 hair are seen about the fifth month of foetal life. The first crop 

 is deciduous, and after covering the body of the foetus like a fine 

 down, till the eighth month of utero-gestation, it then falls off: 

 sometimes, however, it is retained either in whole or in part 

 till after birth ; this is particularly the case in regard to the hair 

 of the head. In this deciduous character we see another analo- 

 gy between the hair and the teeth. 



When the hair becomes white from age, the conversion 

 of colour begins at the loose extremity, another proof of the 

 interstitial circulation, or change of particles in it. The same 

 fact is observable in animals who change colour only for the 

 winter. But the restoration of colour begins at the root. 



It is probable, in those cases of plica polonica attended with 

 bleeding from the root of the hair when it is cut, that the vas- 

 cular papilla has been so much augmented as to elevate itself 

 above the level of the cuticle, and of course interferes with the 

 sweep of the razor employed in shaving the head. Ignorance 

 in regard to the organization of the hair, and a slight inclination 

 to the marvellous, would magnify this into every hair, in such 

 a disease, being a sort of branch-pipe from the general circu- 

 lating system, and therefore bleeding upon being wounded. 

 Many of the victims to this disease accordingly prefer the loath- 

 some matting of the hair with which it is accompanied, to the 

 supposed risk of dying by hemorrhage. 



