254 



THE TISSUES. 



fibrous substance J^ to -$ 

 inch broad, and 73,5^ to 

 faces and irregular edges. 



Fig. 160. 



mate elements of the fibrous substance; each of them consisting of 

 an aggregation of flat fusiform fibre-cells or plates the plates of the 



of an inch long, ^^ to ^Q I QO of an 

 an inch thick, with uneven sur- 

 They very frequently exhibit a darker 

 streak in the interior, and 

 sometimes contain granular 

 pigment. In other respects, 

 they are homogeneous, and 

 present no minuter elements. 

 (Fig. 160.) 



The dark spots, dots, and 

 streaks of the fibrous portion 

 are of three kinds: 1, granu- 

 lar pigment ; 2, cavities filled 

 with air or fluid; 3, nuclei. 

 The pigment granules are de- 

 posited in the plates of the 

 hair, are especially abundant 

 in dark hairs, and vary much 

 in their size and form. The 

 cavities filled with air appear 

 in the form of round dots ; 



diameter; or of longish streaks 

 3 ._i ou of an inch in length, 

 and -5^3 to T 5 J^ of an inch 

 in breadth, running parallel 

 with the axis of the hair. 

 They are most frequent in 

 white hairs, and often occur 

 in fair, bright brown, and 

 bright red hairs, in great 

 numbers. They are absent 



Plates, or fibre-cells of fibrous substance of the hair, . -. i i j ^ 



treated with acetic acid. A. Isolated plates. 1. From l Ib, ctiiu 



the surface (3 single, 2 united.) 2. From the side. B. roo t of all hairS. The nuclei 



ties of the pigment spots, and are 



connected with the extremi- 

 to ^ of an inch long, by 



