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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
very distinct in the follicles of minute hairs; it is limited to the deeper part of the follicle. Outside this is a compact layer of fibers 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 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.


FIG. 944– Section of skin, showing the epidermis and dermis; a hair in its follicle; the Arrector pili muscle; sebaceous glands. (See enlarged image)

  The inner or epidermic coat is closely adherent to the root of the hair, and consists of two strata named respectively the outer and inner root sheaths; the former of these corresponds with the stratum mucosum of the epidermis, and resembles it in the rounded form and soft character of its cells; at the bottom of the hair follicle these cells become continuous with those of the root of the hair. The inner root sheath consists of (1) a delicate cuticle next the hair, composed of a single layer of imbricated scales with atrophied nuclei; (2) one or two layers of horny, flattened, nucleated cells, known as Huxley’s layer; and (3) a single layer of cubical cells with clear flattened nuclei, called Henle’s layer.
  The hair bulb is moulded over the papilla and 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 center 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 in

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