ii4 



HAIRS. 



[sect. 63. 



sheath, which never present fissures between them. These (fig. 

 50, B.), which constitute a simple or double layer [Huxley's layer), 

 are shorter aud broader than the cells above described (0*014'" to 

 0*018'" long, 0*006'" to 0-009'" broad); likewise, however, poly- 

 gonal, and possess, at least in the lower half of the root-sheath, 

 distinct, elongated, often pointed nuclei, 0*004'" to 0*006'". The 

 thickness of the entire inner root-sheath amounts, on an average, 

 to o*oo&'" to 0*015'"; whence it is evident that its cells, which at 

 most form three layers, are at least 0*002'" to 0*005'" in thickness. 

 They can be seen without preparation in their natural position, 

 and by teasing out the root-sheath ; they are easily isolated in soda 

 and potash, without, however, swelling up — a character which, as 

 well as their considerable resistance to the actions of alkalies in 

 general, they share with the cuticular plates of the hair. 



At the bottom of the hair-follicle, the proper inner root-sheath 



Fig. 50. 





Elements of the inner root-sheath, magnified 350 times. A. From the outer layer. 1. 

 Isolated plates of the same ; 2. the same in connection, from the uppermost parts of the 

 layer in question, after treatment with caustic soda. a. Openings between the cells b. 

 B. Cells of the inner uninjured layer, with elongated and slightly dentated nuclei. C 

 Nucleated cells of the lowermost part of the inner sheath, which consists of a single layer. 



consists of only a single layer of beautiful, large, polygonal, nu- 

 cleated cells without openings between them, which, becoming 

 at last soft, delicate, and roundish, pass into the external layers of 

 the round cells of the hair-bulb, without any sharp line of demar- 

 cation. Superiorly, this investment is not unfrequently somewhat 

 separated from the hair. It terminates near the openings of the 

 sebaceous glands in a sharp, dentated border, which is formed by 



