230 NORMAL HISTOLOGY. 



the papillae ; directly covering the latter are cylin- 

 drical and cuboidal cells, corresponding to those of 

 the rete Malpighi, which gradually become changed 

 in shape, and more or less horny, and form the sub- 

 stance of the hair-shaft. 



In the shaft we recognize three portions: I. A 

 central or medullary portion, composed of cuboidal 

 or more or less flattened cells, not infrequently en- 

 closing between them tiny bubbles of air, which 

 give the centre of the hair a dark appearance by 

 transmitted light. Outside of this is 2, the cortical 

 portion, making up the larger part of the bulk of 

 the shaft, and composed of tough, horny, elongated, 

 flattened cells closely packed together, and having 

 within and between them, except in colorless hairs, 

 granules of variously-colored pigment. In that por- 

 tion of the hair which lies within the follicle, and 

 between the bulb and the free shaft, we find, while 

 the hair is growing, that the cells of the cortical 

 layer are larger, less flattened and horny, and, as 

 above mentioned, merge into the large cylindrical 

 and spheroidal cells of the bulb. Finally, the shaft 

 is covered, 3, by the so-called cuticula, consisting of 

 thin rectangular, non-nucleated, scale-like cells, which 

 lap over one another, so that the lower cells, i. e., 

 those nearest the root of the hair, cover a portion of 

 the cells beyond, and these free edges often project 

 slightly from the surface of the hair, giving it a 

 finely serrated appearance. 



