THE SKIN AND ITS APPKXDAGES 



395 



The cuticle of the root sheath Hes against the cuticle of the hair 

 and is similar to the latter in structure. It consists of thin scale-like 

 overlapping cells, nucleated in the deeper ])arts of the sheath, non- 

 nucleated nearer the surface (Figs. 280, 281 unci 282, c). 



Huxley's layer lies immediately outside the cuticle of the root 

 sheath, constituting the middle layer of the inner root sheath. It 

 consists of about two rows of elongated cells with slightly granular 

 protoplasm containing eleidin. In the deeper portion of the root 

 these cells contain nuclei. Nearer the 



a h c 



surface the nuclei are rudimentary or 

 absent (Figs. 280, 281 and 282, d). 



Henle's layer is a single row of clear 

 flat cells. In the bulb these cells may 

 contain nuclei; elsewhere they are non- 

 nucleated (Fig. 282, e). 



(b) The outer root sheath is derived 

 from the stratum germinativum to 

 which it corresponds in structure. 

 Next to the vitreous membrane is a 

 single layer of columnar cells (stratum 

 cyhndricum) . Inside of this are several 

 layers of "prickle" cells (Figs. 280, 281 

 and 282, /). 



(2) The connective-tissue follicle con- 

 sists of three layers — an inner vitreous 

 membrane, a middle vascular layer, and 

 an outer fibrous layer. 



(a) The vitreous or hyaHne membrane is a thin homogeneous 

 structure of the nature of an elastic membrane. It lies next to the 

 outer root sheath and corresponds to the basement membrane of the 

 derma (Figs. 280, 281 and 282, g). 



(b) The middle or vascular layer is composed of fine connective- 

 tissue-fibres, the general arrangement of which is circular. Cellular 

 elements are quite abundant, while elastic fibres are, as a rule, absent. 

 As its name would indicate, this layer is especially rich in blood- 

 vessels (Figs. 280, 281 and 282, i). 



(c) The outer or fibrous layer consists of rather coarse, loosely 

 woven bundles of white fibres, which run mainly in a longitudinal 

 direction. Among these are elastic fibres and a few connective- tissue 

 cells. 



Fig. 279. — Longitudinal Section 

 of Hair. X350. (KoUiker.) a, 

 Medulla; b, cortex; c, cuticle. 



