OF THE HAIRS. 



109 



Fig. 63. 



I 



least in its lower part ; in living hairs it ends in a still softer 

 knob-like enlargement, l\ to 3 times thicker than the shaft, — 

 the " bulb of the hair" (c), which is 

 placed, cap-like, upon a papillary 

 process of the sac, the "hair-papilla" 

 (less properly termed pulpa, or blas- 

 tema pili, hair-germ), or, in other 

 words, receives the papilla in an ex- - £ 



cavation in its base. 



§ 54. 



Disposition and size of the Hairs. 

 — The hairs are distributed over al- 

 most the whole surface of the body, 1 

 but exhibit very considerable differ- 

 ences in size and number, according 

 to their situation, to individual pecu- 

 liarity, age, sex, and race. As regards 

 the former, three varieties may be 

 admitted, besides many transitional 

 forms : (1) long soft hairs, of 1' — 3' 

 and more in length, 002 — O'Oo'" in 

 thickness ; (2) short stiff thick hairs, 

 of I — |" in length, and 003— 007'" 

 in thickness ; (3) short, excessively- 

 fine hairs, down {lanugo), of 1 — 6'" 

 in length, and 0-006 — 001"' in 

 thickness. The distribution of the first form is well known ; 

 to the second belong the hairs at the entrance of the nostrils 

 [vibrissa), in the external auditory passage, the eyelashes 

 (cilia), and eyebrows; to the third, finally, must be referred 



Fig. 63. Hair and hair sacs of middling size, x 50 : a, hair shaft ; b, root of the 

 hair; c, bulb of the hair ; d, epidermis of the hair; e, inner root-sheath ; /outer 

 root-sheath ; g, structureless membrane of the hair sac ; //, transversely and longitu- 

 dinal fibrous layer thereof; i, papilla of the hair; k, excretory ducts of the seba- 

 ceous glands, with epithelium and layers of fibres ; /, cutis at the aperture of the hair 

 sac ; m, stratum mucosum ; n, horny layer of the epidermis, the latter somewhat re- 

 tracted into the sac; o, end of the inner root-sheath. 



1 [No hairs exist upon the upper eyelids, the lips, the palm of the hand, and sole 

 of the foot ; nor on the dorsum of the last joints of the fingers and toes, the inner 

 surface of the prepuce, and the glans penis. — Eds.] •" 



