OF THE HAIRS. 



191 



63. Shedding of the Hair. After birth, a total shedding of the 

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

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

 shedding 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 



Fig. 76. Fig. 77. 





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

 becomes converted into horn even in its lowermost por- 

 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. 76. The eyelashes of a child of one year old pulled out; magnified 20 diameters: 

 d, 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; 'J3, eyelash in whose process, of 0'3 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; 6, 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 ; /, transition of the outer root-sheath into the rete 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. 70. 



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 lias attained this form it goes on growing; but once having reached it, 

 it grows no more, but falls out and is replaced by a new hair (see following ). Tns.] 



