246 SKIN, HAIR, AND NAILS, BY ALFRED BIESIADECKI. 



the sheaths of the hair follicles. Langerhans (loc. tit.) describes 

 nerve cells between the cells of the external root-sheath similar 

 to those of the rete mucosum. 



The internal root-sheath (g) is composed of two layers, an 

 outer and an inner. The outer layer is the inner root-sheath 

 of Henle ; the inner, the so-called sheath of Huxley. In regard 

 to their development, their composition, and their chemical 

 characters, these two structures are perfectly distinct. The 

 first is genetically connected with the external root-sheath, whilst 

 the latter is developed with the hair itself from the bulb. 



The internal root-sheath of Henle appears in longitudinal 

 sections of the hair as a thin, transparent, and refractile layer, 

 scarcely staining with carminate of ammonia, and closely re- 

 sembling the vitreous membrane. It begins at the neck of 

 the hair follicle, and only extends towards the bulb as far as 

 the external root-sheath. Externally it is sharply defined from 

 the external root-sheath, whilst internally it is in contact with 

 the sheath of Huxley, that will be subsequently described. 



The first-named sheath, originally described by Henle, by 

 whom it was named the inner root-sheath, consists, as is shown 

 by sections and surface views, of oblong, non-nucleated, highly 

 refractile scales, running parallel to the long axis of the hair 

 follicle, and resembling vertically-divided fusiform cells. The 

 plane surfaces of these spindle-shaped cells are applied to the 

 external root-sheath, over which they form a continuous layer, 

 whilst their internal convex surfaces touch the cells forming 

 Huxley's sheath. 



The greater number of anatomists have described small 

 fissures between these scales, and the presence of these has led 

 Henle to describe it as a fenestrated membrane ; on the other 

 hand they have been regarded as small holes produced by the 

 manipulation requisite for the isolation of the sheath. 



There can be no doubt that, in surface views, without 

 previous isolation of the sheath, appearances are seen that 

 speak in favour of the presence of fine fissures between 

 the scales. These apparent fissures, however, are produced 

 by the focussing of the internal surface of the cells, that, as 

 already stated, are convex, whereby sometimes broader, some- 

 times narrower slits appear, according as the cells brought 



