THE SKIN. 563 



question how a new growth of epithelia goes on, replacing the 

 lost epidermal scales, is as yet not quite settled. In persons of 

 dark complexion the horny epithelia also exhibit a diffuse yel- 

 low-brown color. 



(7) Implantation of the Hairs* If we imagine that the connect- 

 ive tissue, together with the covering epithelium, were a pliable 

 sheet of chamois, for instance, and we produce a depression of 

 this sheet with one of our fingers, the result will be a pouch, whose 

 innermost layers are epithelial, whose outermost layer is connect- 

 ive tissue. The epidermis will cover the inner surface of the 

 pouch, and now bear the name inner root-sheath; next to this 

 will be a layer formed by the epithelia of the rete mucosum, 

 which will be the outer root-sheath; the outside of the pouch 

 must be connective tissue, and will represent the follicle. At the 

 bottom of the pouch will be a protrusion of the follicle, similar 

 to those on the surface of the skin, therefore connective tissue 

 the papilla of the hair. 



On our diagram slight alterations must be made. The epi- 

 dermis, which is composed of a large number of flat epithelia, 

 varying greatly according to the width of this layer, upon enter- 

 ing the pouch and becoming the inner root-sheath, will gradually 

 be reduced to a limited number of horny epithelia in the middle 

 of the pouch to not more than two strata. Near the bottom of 

 the pouch the number of the epithelia again increases, the inner 

 root-sheath gains in width, and is composed of three or four 

 strata of epithelia which have lost their horny character, and 

 assume again the nature of bioplasson. The rete mucosum 

 enters the pouch in its full width, but gradually becomes thinner, 

 namely, composed of a smaller number of epithelia, which 

 retain their original bioplasson character, and at last, near the 

 bottom of the pouch, after being reduced to a single layer, com- 

 pletely disappears. 



Imagine, now, that against the bottom of the epithelial pouch, 

 which runs in an oblique direction, corresponding with the dis- 

 position of the connective-tissue bundles, a pin is pressed and the 

 pouch turned upward again. This procedure, of course, will 

 involve the inner root-sheath exclusively, and an elongation must 

 result of an epidermal character, agreeing with the main features 

 of the inner root-sheath. This elongation represents the hair. 



* " A Contribution to the Minute Anatomy of the Skin." Read before the 

 American Dermatological Association, Newport, R. I., September 1, 1881. 

 The Chicago Medical Journal and Examiner, December, 1881. 



