CH. XL.] 



THE HAIRS 



607 



scales, imbricated downwards, which fit over the scales of the cuticle 

 of the hair itself. 



FIG. 390. Longitudinal section of a 

 hair follicle, a and b, External root- 

 sheath ; c, internal root-sheath ; 

 d, fibrous layer of the hair ; e, me- PlO- 391. Transverse section of a hair and hair follicle 

 dulla; /, hair papilla; g, blood- made below the opening of the sebaceous gland, 



vessels of the hair papilla; h, . Medulla, or pith of the hair; b, fibrous layer; 



uermic coat. (Cadiat.) c, cuticle; d, Huxley's layer; c, Henle's layer of 



internal root-sheath ; / and g, layers of external root- 

 sheath, outside of g is the basement membrane or 

 hyaline layer ; h, dermic (fibrous) coat of hair follicle ; 

 i, vessels. (Cadiat.) 



A small bundle of plain muscular fibres is attached to each 

 follicle (fig. 389). When it contracts, as under the influence of cold, 

 or of certain emotions such as fear, 

 the hair is erected and the whole 

 skin is roughened (" goose skin "). 

 The nerves supplying these muscles 

 are called pilo-motor nerves. The 

 distribution of these nerves closely 

 follows those of the vaso-constrictor 

 nerves of the skin; their cell-sta- 

 tions are in the lateral sympathetic 

 chain. 



The sensitiveness of the hairs or 

 more properly of the hair follicles 

 is subserved by a ring-like plexus Fl 

 of nerve-fibrils around the hair 

 follicle, within the outer sheath, 

 just beneath the entrance of the sebaceous gland (see fig. 392). 



392. Sensory nerve ending of hair fol- 

 licle. Gold chloride; preparation. x 900. 

 (Szymonowicz.) 



