270 



NORMAL HISTOLOGY. 



Below the openings of the sebaceous glands the hair- follicle 

 consists of the fibrous coat and the stratum mucosum of the epi- 

 dermis only : at its upper extremity the stratum corneum additionally 

 takes part in the formation of the follicle. The fibrous coat of the 

 follicle consists of three layers : the outer, composed of longitudinally- 

 placed bundles of connective tissue, rich in cells, and representing a 

 condensation of the tissue of the corium ; the middle, represented 

 by a layer of circular connective-tissue bundles continuous with the 

 papillary layer of the cutis ; and the inner, a clear, homogeneous, 

 narrow but conspicuous zone, the glassy or hyaline membrane. 

 The latter separates the epithelium from the surrounding fibrous 

 tissue, and corresponds to a highly-developed basement-mem- 

 brane. These layers of the fibrous sheath are not continued to an 

 equal extent over the hair-follicle ; the outer longitudinal layer com- 

 pletely invests the follicle, becomes continuous with the corium, and 

 materially aids in maintaining the form of the follicle. The circular 



FIG. 307. 



Transverse sections of hair-follicles 

 from human scalp : a, hair; , cuticle 

 of hair; c, d, inner and outer root- 

 sheath ; e, glassy membrane ;f, fibrous 

 sheath ; g, surrounding connective 

 tissue of corium ; k, fat-cells. 



Transverse section of hair-follicle from human scalp ; 

 plane of section passes through mouth of follicle : a, 

 one of the hairs; b, horny tissue of superficial layers 

 of epidermis ; c , cells of stratum Malpighii ; d, sur- 

 rounding connective tissue. 



layer extends from the base of the hair-follicle to the orifices of the 

 sebaceous glands, while the glassy membrane, as such, ceases at the 

 mouth of the follicle. 



Next inside the glassy membrane follow the epithelial layers occu- 

 pying the entire space between the hair and the sides of its follicle. 

 The epithelial tissue is disposed in two well-marked strata, the 

 thicker, many-layered zone next the glassy membrane, which con- 

 stitutes the outer root-sheath, and the much thinner concentric 

 layer composing the inner root-sheath. The former is the direct 

 prolongation of the stratum mucosum of the general integu- 



