Chap. XXXIV.] 



THE SKIN. 



283 



tioned. They can be isolated by strong acids and 

 alkalies. In pigmented hairs there occur numerous 

 pigment granules between the hair fibres, but also 

 diffused pigment in their substance. The same is 

 noticed with reference to the hair-bulb viz., pigment 

 granules being present in the intercellular cement, 

 and pigment also in the cell substance. In the centre 

 of many hairs is a cylindrical space, containing gene- 

 rally one row of polyhedral cells, which are, to a great 

 extent, filled with air, and, in pigmented hair, also 

 with pigment granules. 



384. On the surface of the hair substance is a thin 

 cuticle, a single layer of horny non-nucleated hyaline 

 scales arranged more or less transversely ; they are 

 imbricated, and, according to the degree of imbrica- 

 tion, the cuticle shows more or less 



marked projections, which give to the 

 circumference of the hair the appear- 

 ance of minute teeth, like those of a saw. 



385. The inner root-sheath in well- 

 formed, thick hairs, is very distinct, 

 and consists of a delicate cuticle next 

 to the cuticle of the hair ; then an 

 inner, or Huxley's, layer, which is a 

 single, or sometimes double, layer of 

 horny cubical cells, each with a rem- 

 nant of a nucleus ; and, finally, an 

 outer, or Ilenle's, layer a single layer 

 of non-nucleated horny cubical cells. 



The shaft of the hair (Fig. 

 149), or the part projecting over 

 the free surface of the skin, is of 

 exactly the same structure as the root, except that it 

 possesses no inner root-sheath. 



386. As mentioned above, at the hair-bulb the 

 polyhedral cells constituting this latter gradually pass 

 into the different parts of the hair i.e., marrow-sub- 



149. Longitu- 

 dinal View of the 

 Shaft of a Pi fo- 

 mented Human 

 Hair. 



a, Marrow of hair ; 

 6, nbres of hair sub- 

 stance ; c, cuticle. 



