442 BULBS OF THE HAIRS. 



the color of the rete mucosum, as it is so generally black 

 when the rete mucosum is dark colored. 



The sudden change of color in consequence of fright or 

 grief, is a very rare occurrence indeed ; but Bichat relates 

 an instance which came under his observation, in which the 

 hair became perfectly white in one night, in consequence of 

 grief. 



The substance of the hair is of a corneous nature like the 

 epidermis. Each hair consists of two parts, a bulb or follicle, 

 and a stalk or hair proper. 



The follicle is ovoidal, and consists of two membranes. The 

 exterior is white, firm, and continuous with the cutis vera ; the 

 interior, which is thin, soft and reddish, appears to be continuous 

 with the corneous layers. 



The cavity of the follicle is filled up at the bottom with a 

 conical papilla, into which, according to Beclard, the nerves 

 and blood-vessels may be seen running below. Rudolphi and 

 Andral, have traced nerves into the whiskers of the seal ; 

 Shaw has done the same, and discovered that they were 

 branches of the fifth pair. The root of the hair possesses a coni- 

 cal cavity, in which is lodged the point of the papilla which 

 appears to secrete the matter of the hair, and cause its growth, 

 by the continuous deposition of new matter at its root, as takes 

 place in regard to the nails of man, and the horns of animals ; 

 this deposit of new matter in the fluid state, has been seen 

 between the hair and papilla. It is sometimes secreted in pro- 

 fusion, especially in the head ; and has appeared to me, by over- 

 flowing from the follicles, and drying in the form of scales, to 

 be the source of the dandriff. 



The epidermis is reflected from the mouth of the follicle, and 

 lost upon the surface of the hair. 



The hair, when examined with the microscope, appears to 

 be covered externally with small scales, and to be hollow inter- 

 nally. The latter, however, is as regards the human hair, an 

 optical illusion, as it is merely loose and porous or pith-like in 

 its central part. The stalks of hairs have neither vessels nor 

 nerves in their structure, and anatomists no longer admit 



