284 



THE SKIN 



brane, the papillary layer, and the reticular layer of the derma, respec- 

 tively. The dermal root sheath is, however, devoid of papilla?. 



a b 



FIG. 274. TRANSECTION OF A HAIR NEAR THE MIDDLE OF THE ROOT SHEATH. 



a, dermal root sheath; b, outer margin of the epidermal root sheath the light 

 space is the glassy membrane, the polyhedral cells form the outer root sheath; c, 

 Henle's layer of the inner root sheath; d, Huxley's layer; e, cuticle of the root sheath; 

 /, cuticle of the hair; g, cortex of the hair shaft. Highly magnified. (After Kolliker.) 



The glassy membrane is a peculiarly thick homogeneous membrane 

 which is chiefly mesoblastic in origin, but whose innermost portion is 

 formed as an exoplasmic product of the adjacent epithelium. This 



