1162 



THE ORGANS OF SPECIAL SENSE 



with nerve fibrils. In structure the hair follicle consists of two coats an outer 

 or dermic, and an inner or epidermic (Figs. 877 and 879). 



The outer or dermic coat is formed mainly of fibrous tissue; it is continuous 

 with the corium, is highly vascular, and is supplied by numerous minute nerve 

 filaments. It consists of three layers. The most internal, the cuticular lining 

 of the follicle, consists of a hyaline basement membrane, the hyaline layer, having 

 a glassy, transparent appearance, which is well marked in the larger hair follicles, 

 but is not very distinct in the follicles of minute hairs. It is continuous with the 

 basement membrane of the surface of the corium. External to this is the inner 

 fibrous layer, a compact layer of fibres and spindle-shaped cells arranged circularly 

 around the follicle. This layer extends from the bottom of the follicle as high as 

 the entrance of the ducts of the sebaceous glands. Externally is the outer fibrous 

 layer, a thick layer of connective tissue, arranged in longitudinal bundles, forming 

 a more open texture and corresponding to the reticular part of the corium. In this 

 are contained the bloodvessels and nerves. 



CUTICLE OF 

 ROOT SHEATH 



HENLE'S 

 LAYER 



INNER 



FIBROUS > 



LAYER 



OUTER 



FIBROUS 1.' 



LAYER '; 



HUXLEY'S 

 LAYER 



x MEDULLARY 

 SUBSTANCE 



l&jjf N FIBROUS 



SUBSTANCE 



FIG. 879. A moustache hair with its hair follicle in transverse section. (Toldt.) 



The inner or epidermic layer is closely adherent to the root of the hair, so that 

 when the hair is plucked from its follicle this layer most commonly adheres to it 

 and forms what is called the root sheath. It consists of two strata, named respec- 

 tively the outer and inner root sheaths; the former of these corresponds with the 

 Malpighian layer of the epidermis, and resembles it in the rounded form and 

 soft character of its cells; at the bottom of the hair follicles these cells become 

 continuous with those of the root of the hair. The inner root sheath consists of 

 a delicate cuticle next the hair, composed of a thin layer of imbricated scales having 

 a downward direction, so that they fit accurately over the upwardly directed 

 imbricated scales of the hair itself; then of one or two layers of horny, flattened 

 nucleated cells, known as Huxley's layer; and finally of a single layer of horny 

 oblong cells without visible nuclei, called Henle's layer. 



The hair follicle contains the root of the hair, which terminates in a bulbous 

 extremity, and is excavated so as to exactly fit the papilla from which it grows. 

 The bulb is composed of polyhedral epithelial cells, which as they pass upward 

 into the root of the hair become elongated and spindle-shaped, except some in 

 the centre, which remain polyhedral Some of these latter cells contain pigment 

 granules, which give rise to the color of the hair. It occasionally happens that 

 these pigment granules completely fill the cells of the medullary substance in 

 the centre of the bulb, which gives rise to the dark tract of pigment often found, 

 of greater or less length, in the axis of the hair. 



