OF THE HAIRS. 



171 



Fig. 63. 



III. OF THE HAIRS. 



53. In every hair we distinguish the free part or shaft, scapus, with 

 its tapering point, from the portion enclosed within the sac, the root, 

 radix. In straight hairs the former is generally straight and rounded; 

 in the wavy, undulated and somewhat flattened ; in the curly and woolly 

 hairs, it is twisted spirally and quite flat or 

 slightly ribbed. The root is always straight, 

 tolerably cylindrical, and softer and thicker 

 than the shaft, at least in its lower part ; 

 in living hairs it ends in a still softer knob- 

 like enlargement, 1|- to 3 times thicker 

 than the shaft, the " bulb of the hair" (<?), 

 which is placed, cap-like, upon a papillary 

 process of the sac, the " hair-papilla" (less 

 properly termed pulpa or blastema pili, 

 hair-germ), or in other words receives the 

 papilla in an excavation in its base. 



4 



54. Disposition and Size of the Hairs. 

 The hairs are distributed over almost the 

 whole surface of the body,* but exhibit very 

 considerable differences in size and number, 

 according to their situation, to individual 

 peculiarity, age, sex, and race. As regards 

 the former, three varieties may be admitted, 

 besides many .transitional forms: (1) long 

 soft hairs, of 1-3 feet and more in length, 

 0-02-0-05 of a line in thickness; (2) short 

 stiff thick hairs, of J-J of an inch in length, 

 and 0-03-0-07 of a line in thickness ; (3) 

 short, excessively-fine hairs, down (lanugo), 

 of 1-6 lines in length, and 0-006-0-01 of a line in thickness. The dis- 

 tribution of the first form is well known; to the second belong the hairs 

 at the entrance of the nostrils (vibrissce), in the external auditory 

 passage, the eyelashes (cilia), and eyebrows; to the third, finally, must , 

 be referred the hairs on the face, trunk, and extremities, also those of 



FIG. 63. Hair and hair sacs of middling size; magnified 50 diameters: 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 ; h, transversely and longitudinal 

 fibrous layer thereof; t, papilla of the hair; k, excretory ducts of the sebaceous glands, with 

 epithelium and layers of fibres ; I, cutis at the aperture of the hair sac ; m, stratum mucosum ; 

 n, horny layer of the epidermis, the latter somewhat retracted into the sac; o, end of the 

 inner root- sheath. 



* [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. TRS.] 



