118 THE MECHANICAL FUNCTIONS. 



attachment excepting at the lower part, v, where 

 the vessels and nerves of the pulp are passing 

 into it. The hair, growing by depositions from 

 the inside of the capsule, which forms the outer 

 part, o, of the shaft, and from the outside of the 

 pulp, which forms the inner or central part, i, is 

 forced upwards till it has pierced the skin ; and 

 in the course of its passage a canal is formed for 

 it in the skin itself, and continuous with that 

 which encloses the bulb : and the course of this 

 canal is generally oblique. In the elephant, 

 where the thickness and density of the hide, 

 present considerable obstacles to the passage 

 of the hairs through it, we may discover, on 

 minute examination, many hairs that have only 

 penetrated a certain way, as shown at B, without 

 ever succeeding in reaching the surface. 



An opinion has been very commonly enter- 

 tained that each hair, on its protruding from 

 underneath the cuticle, E, at the point Q, carries 

 up along with it a portion of this outer integu- 

 ment, which, stretching as the hair increases in 

 length, forms over it a very fine external tunic. 

 But later observations have shown that this is 

 not the case, and that there is simply an ad- 

 hesion of the edge of the cuticle to the origin of 

 the hair, without any accompanying prolonga- 

 tion ; so that if the whole bulb be destroyed, and 

 its pulp absorbed, the hair may be detached by 

 the slightest force. 



