HAIR. 



[ •'^08 ] 



HAIR. 



of pressure; they then become separated 

 (fig. 301 ), the inner, with the root of the hair, 

 assuming an undulating form, and remaining 

 firmly adherent (c); whilst the outer {d) re- 

 mains attached to the inner root-sheath, its 

 cells also being broad and without nuclei. 

 At the bulb, both these layers become trans- 

 formed into soft cells, broader than long, 

 with transverse nuclei, finally becoming fused 

 with the round cells of the bulb. 



The hair-follicles are pouches, about 1-10 

 to 1-4" in length, pretty closely surrounding 

 the hairs, and extending in the short hairs 

 into the substance of the upper layer of the 

 cutis ; but in the long hairs, into its deepest 

 portion, or even into the subcutaneous cel- 

 lular tissue. They may be regarded as pro- 

 longations of the skin, with its components, 

 the cutis, basement-membrane, and epider- 

 mis. Hence three parts are distinguishable 

 in them : an external, fibrous, very vascular 

 portion, the proper hair-follicle, a basement- 

 membrane, and a non-vascular cellular coat, 

 — the epidermis of the follicle, or, because it 

 surrounds the root of the hair, the root- 

 sheath. 



The fibrous portion of the follicle consists 

 of two layers or membranes. The outer one 

 (fig. 296 h) is the thicker, and contains ves- 

 sels and nerves. Its inner surface is con- 

 nected with the inner layer ; externally it is 

 attached to the surrounding areolar tissue ; 

 and above it is continuous with the outer 

 layer of the cutis. It consists of common 

 areolar tissue, the fibres of which are longi- 

 tudinal, with elongated, spindle-shaped nu- 

 clei. The inner layer (fig. 304 a) is much 

 more delicate, and only extends from the 

 base of the hair-follicle to the orifice of the 

 sebaceous follicles. It consists of a single 

 layer of transverse fil)res, vdth long and nar- 

 row nuclei, resembling unstriated muscular 

 fibres. 



The third layer (fig. 304 h), or basement- 

 membrane, is transparent and structureless, 

 and extends from the base of the follicle, 

 without apparently covering the papilla, as far 

 as the inner root- sheath, and perhaps higher. 

 It presents delicate transverse anastomos- 

 ing lines, producing a fibrous appearance. 



The pulp or papilla of the hair (fig. 296 i) 

 belongs to the follicle, and corresponds to a 

 papilla of the skin. It is rounded or oval, 

 1-96 to 1-480" in length, is connected with 

 the fibrous coat of the follicle by a kind of 

 stalk, and consists of indistinctly fibrous 

 areolar tissue with nuclei and granules of 

 fat, but contains no cells. 



a 



Magnified 300 diameters. 



Portion of the inner fibrous coat and basement-mem- 

 brane of a bair-follicle : a, inner coat with transverse 

 fibres and elongated transverse nuclei ; b, basement- 

 membrane, seen as it were in section ; c, its lacerated 

 margins ; d, fine lines (fibres ?J on its inner surface. 



The two root-sheaths consist of the epi- 

 dermic covering of the hair-follicle. The 

 outer (fig. 296/) is the continuation of the 

 rete mucosum of the skin, and lines the en- 

 tire follicle. Its lower part is in contact 

 externally with the basement membrane of 

 the follicle; but above the termination of 

 the inner transverse layer of the follicle, it is 

 in direct contact with the outer or longitu- 

 dinal layer. It consists of several layers of 

 nucleated cells, resembling those of the rete 

 mucosum of the skin, the outer having their 

 long axis perpendicular to that of the hair ; 

 the others, especially towards the bulb, being 

 rounded. This outer root-sheath is most 

 distinct in the follicles of the skin of the 

 negro, from which it may be withdrawn with 

 the epidermis after maceration. 



The inner root-sheath (fig. 301, e, /) forms 

 a transparent, very firm and elastic, yellowish 

 membrane, extending from near the base of 

 the hair-follicle to near the mouths of the 

 sebaceous follicles, where it terminates ab- 



