134 



THE ESSENTIALS OF HISTOLOGY. 



of the cutis vera. Its fibres and cells have a regular circular arrange- 

 ment around the follicle, the cells being flattened against the hyaline 

 layer. Externally the dermic coat of the follicle has a more open 

 texture, corresponding to the reticular part of the cutis, and containing 

 the larger branches of the arteries and veins. In the large tactile 

 hairs of animals, the veins near the bottom of the follicle are dilated 

 into sinuses, so as to produce a kind of erectile structure. 



FIG. 158. LONGITUDINAL SECTION THROUGH THE FOLLICLE OF A HAIR WHICH HAS. 

 CEASED TO GROW. (Ranvier.) 



m, epithelium at the bottom of the follicle (which contains no papilla) ; I, modified hair-bulb ; 

 c, neck of the follicle ; s, sebaceous gland ; o, epithelial projection at the insertion of the 

 arrector pili. 



The hair grows from the bottom of the follicle by multiplication of 

 the soft cells which cover the papilla, these cells becoming elongated to 

 form the fibres of the fibrous substance, and otherwise modified to pro- 

 duce the medulla and cuticle. 



When a hair is eradicated, a new hair is produced from these cells. 

 It is not uncommon to find hair-follicles in which the whole of the lower 

 part has degenerated in such a way that the vascular papilla, and the 

 soft, growing cells which cover it, may have entirely disappeared, the 



