STRUCTURE OF THE HAIRS. 443 



a fluid in their interior described by Bichat and others as the 

 marrow.* 



Around the orifices of the follicle, and in the substance o/its 

 neck according to Gaultier, we find a number of minute 

 sebaceous glands, that secrete an unctuous fluid, which 

 imbues the hair and preserves its softness and pliability. The 

 hairs are hygrometrical, and increase in length and thickness 

 when exposed to humidity ; and are shortened again by dry heat. 

 From the changes which take place in regard to the color 

 of the hair, there is reason to believe, that it is traversed by 

 some fluid. This passes along the hair by imbibition, from 

 the root upwards, in consequence of its hygrometrical nature, 

 passing up through the spongy or cellular tissue of which the 

 body of the hair appears to be formed. This fluid is 

 derived from the surface of the skin forming the papilla, and 

 is analogous to the fluid of the rete mucosum, and corresponds 

 more or less in color with that of the skin and iris. 

 The hairs vary much in size, but appear all to be constructed 

 on the same plan. They have different names in different parts 

 of the body, as beard, whiskers, eyelashes, &c. The minute 

 hairs generally spread over the body, are called down or 

 duvette, and those which cover the scalp, in man, have particu- 

 larly appropriated to them the term of hair. In the white or 

 Caucasian variety of the human race, the hairs of the head are 

 very numerous, fine, long, and vary in color from white to 

 black : in the Mongolian they are straight, black and short : 

 in the Negro, black, fine, thick and crisped : in the Indian, 

 black, straight, fine and thick: and in the Malay, thick and 

 frizzled. 



Their size and number vary in regard to their color. 

 Withoff, has calculated that in a quarter of an inch square of 

 skin there are one hundred and forty-seven black hairs, one 

 hundred and sixty-two chestnut, and one hundred and eighty- 

 two, blond. 

 The hairs are composed chemically, agreeably to Vauquelin, 



4 



* Note to Bichat, 4th edit. Paris. 



