. Elements of histology. Histology. 414 Elements of Histology. a I. •384. On the surface of the haii--substance is a thin cuticle, a single layer of horny non-nucleated hyaline scales arranged more or less transversely; they are imljiicated, and, according to the degree of imbrica- tion, the cuticle shows more or less marked projec- tions, which give to the circumference of the hair the appearance of minute teeth, like those of a saw. 385. The inner root-sheath in well-formed, thick hairs is very dis- tinct, and consists of a delicate cuticle next to the cuticle of the hair ; then an inner, or
. Elements of histology. Histology. 414 Elements of Histology. a I. •384. On the surface of the haii--substance is a thin cuticle, a single layer of horny non-nucleated hyaline scales arranged more or less transversely; they are imljiicated, and, according to the degree of imbrica- tion, the cuticle shows more or less marked projec- tions, which give to the circumference of the hair the appearance of minute teeth, like those of a saw. 385. The inner root-sheath in well-formed, thick hairs is very dis- tinct, and consists of a delicate cuticle next to the cuticle of the hair ; then an inner, or Huxley's, layer, which is a single, or sometimes double, layer of horny cubical cells, each with a remnant of a nucleus; and, finally, an outer, or HenleJs, layer—a single layer of non-nucleated horny cubical cells. The shaft of the hair (Fig. 256), or the part projecting over the free surface of the skin, is of exactly the same structure as the root, except that it possesses no inner root-sheath. 386. As mentioned above, at the hair-bulb the polyhedral cells constituting this latter gradually pass into the different parts of the hair— marrow-sub- stance, cuticle, and inner root-sheath—and the con- tinual new production of cells over the jmpilla causes a gradual progression and conversion of the cells, and a corresponding growth in length of the hair. Pigmented hairs, as mentioned above, contain pig- ment granules between— in the interstitial sub- stance cementing together—the hair-fibres, and diffuse pigment in their substance. According to the amount of these pigments, but especially of the interstitial pigment granules (Pincus), the colour of the hair is Fig. —Longitu- dinal View of the Shaft of a Pig- mented Human Hair. ilarroAV of b, fibres of substance ; cuticle. hair ; liaii- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illus
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