392 MANUAL OF HISTOLOGY. 



spindles, or finally disappear completely. The union, however, of these 



Fig. 393. a. Cells of the hair bulb; 

 6, from the first part of the shaft; 

 c, cortical substance treated with 

 sulphuric acid, resolved into sepa- 

 rate plates at d; e and/ are cells 

 f rora the hair cuticle. 



Fig. 392. 



hair-scales, forming the cortical portion, is so intimate that not the slightest 

 indication of their existence appears in the fresh hair (fig. 392, I). Even 

 by mechanical means we can only split off rows of them in the form of 

 rough splinters. Chemically, however, namely, by the aid of sulphuric 

 acid, we are enabled quickly and easily to render visible the elements of 

 the structure by the solution of the matter cementing them together. 



Looking upon the cortical mass as a whole, we find it saturated 

 with a colouring matter varying according to the tint of the hair. Together 

 with this the latter is marked with definite longitudinal streaks, which 

 either represent the borders of adjacent hair-scales, or depend upon the dis- 

 position in rows of the pigmentary molecules, which in darker hairs may 

 make their appearance in large and broad groups. 



Finally, the hard dry consistence of the shaft of the hair favours 

 the entrance of air-bubbles, which frequently occupy small elongated 

 cavities in the interior of the hair-plates. We shall meet again with 

 a far larger accumulation of air in the medullary mass. 



215. 



In the preceding section the presence, from the lower part of the root 

 up, of a peculiar thin enveloping layer, was noticed. This, as it ascends, 

 is known as the cuticle of the hair. Close observation of the bulb at its 

 base (fig. 392) shows us that, from that point on, at which its cells cease 

 to be continued into the external root-sheath, the structure becomes 



