OF THE II A I lis. 



191 



§ 63. Shedding of the Hair. — After birth, a toted shedding of the 

 hairs takes place in consequence of the development of new hairs zvithin 

 the hair-sacs of the lanugo, which gradually force out the old ones. This 

 sliedding of the hairs, which I discovered in the eyelashes of a child of 

 one year old, commences by an outgrowth of the soft round cells of the 

 bulb and of the neighboring outer root-sheath, from the bottoms of the 

 sacs of the lanugo, into long processes composed of cells, by which the 



Fis?. 76. 



Fis. 77. 



i^Ki 



■J I 



hair is raised from its papilla, whilst at the same time it } 

 becomes converted into horn even in its lowermost por- S 

 tion. When these processes have attained a length of ^ 

 0*25 of a line, a differentiation of their outer and inner 

 cells takes place, similar to that which has been already 



Fig. 7G. — Tlie eyelashes of a child of one year old pulled out; magnified 20 diameters: 

 A, one with a process of the bulb or of the outer root-sheath, of 0'25 of a line, in which the 

 central cells are elongated (their pigment is not represented), and are clearly defined as a 

 cone from the external ones; B, eyelash in whose i^rocess, of 03 of a line, the inner cone is 

 metamorphosed into a hair and an inner root-sheath ; the old hair is pushed up, and like A 

 and Fig. 75, possesses no inner root-sheath : a, outer; b, inner root-sheath of the young hair; 

 c, pit for the papilla of the hair; rf, bulb; e, the shaft of the old hair; /, bulb; g, shaft; h, 

 point of the young hair; i, sebaceous glands; k, three sudoriparous canals, which in A open 

 into the upper part of the hair-sac; l, transition of the outer root-sheath into the rele mucosum 

 of the epidermis. 



Fig. 77. — An eyelash with the root-sheaths from a child one year old, with an old and a 

 growing young hair, magnified 20 diameters: the young hair is wholly extruded, and now 

 two hairs appear at one aperture. A sudoriparous canal opens into the hair-sac. The 

 letters have the same signification as in Fig. 7(5. 



structed and narrowed root when complete, so has the hair when it has attained its full 

 growth a peculiarly constructed bulb; and it is not a perfect hair until this peculiar bulb is 

 developed. Until it has attained this form it goes on growing; Init once having reached it, 

 it grows no more, but falls out and is replaced by a new hair (see following §). — Trs.J 



