HAIR. 



[ 371 ] 



HAIR. 



hair depends, and constitutes the greater 

 portion of its bulk. It exhibits numerous 

 longitudinal striae, or interrupted dark lines 

 and dots. When acted upon by strong sul- 



Fig. 292. 



Magnified 50 diameters. 



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

 shaft; 6, root ; c, bulb or knob; d, cuticle of the hair; 

 e, inner sheath of the root ; f, outer sheath of the root ; 

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

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

 Eilla; k, excretory ducts of the sebaceous glands or 

 jllicles, 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 (fig. 293 ) of the most varied sizes, 

 both as to length and breadth ; but if the 

 action of the acid be continued, these fibres 

 become separated into cells (fig. 293 A], 

 These cells present uneven surfaces, and a 

 more or less eliptical outline, their 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 celh 

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



Fig. 293. 



Magnified 350 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 colourless hair, heated with 

 soda or potash (fig. 294 A b, and B} in 

 coloured hair they also contain pigment- 

 granules, to which the colour of the hair is 

 2u2 



