fL\IR. 



[ 371 ] 



PLVIR. 



hair depends, and constitutes the greater 

 portion of its bulk. It exhibits numerous 

 longitudinal striiie, or interrupted dark lines 

 and dots. When acted upon by strong sul- 



Fig. 292. 



I 



i 





i»v. 



a 



MagnifleJ 50 diameters. 



A hair of moderate size, contained in its follicle, a, 

 shaft ; b, root ; c, bulb or knob ; d, cuticle of the hair ; 

 c, inner sheath of the root ; /, outer sheath of the root; 

 g, structureless membrane of the hair- follicle ; h, trans- 

 verse- and longitudinal-fibrous layer of the same ; i, pa- 

 pilla ; k, exc' etory ducts of the sebaceous glands or 

 follicles, with their epithelial and fibrous layer; I, cutis 

 of the orifice of the hair-follicle ; m, rete mucosum ; 

 n, cutaneous epidermis; o, termination of the inner 

 sheath of the root. 



phuric or some other acid at a gentle heat, 

 it becomes at first resolved into plates or 

 fibres (tig. 293 B) of the most varied sizes, 

 both as t^o length and breadth ; but if the 

 action of the acid be continued, these fibres 

 become separated into cells (tig. 293 A). 

 These cells present imeven surfaces, and a 

 more or less eliptical outline, thek true 



form being spindle-shaped ; but they are 

 mostly flattened and angular, or curved from 

 mutual pressure, resulting from their aggre- 

 gation into the shaft of the hair. The cells 

 are about 1-500 to 1-300" iu length, and 



Fig. 293. 





Magnliied 330 diameters. 



Plates and cells of the cortical substance of a hair, 

 after treatment with acetic acid. A, separate cells. 

 1, front view (three of them isolated, two united); 2, 

 side view. B, a layer, composed of several cells. 



from 1-6000 to 1-2200" in breadth. They 

 mostly contain elongated, dark-looking nu- 

 clei, 1-1100 to 1-400" in length ; these are 

 well seen in a coloui-less hair, heated with 

 soda or potash (fig. 294 A h, and B) ; iu 

 coloured hair they also contain pigment- 

 granules, to which the coloiu' of the hair is 



2b2 



