OF THE HAIRS. 



173 



irregular edges; they do not swell up into vesicles on the addi- 

 tion of caustic alkalies, and they very frequently exhibit a 

 darker streak in their interior, F - 64 



of which we shall speak imme- 

 diately; under certain circum- 

 stances they also contain gra- 

 nular pigment; for the rest they 

 are homogeneous, and present 

 no minuter elements, such as 

 fibrillse or the like. They ap- 

 pear to be more strongly united 

 longitudinally, than in the 

 direction of their breadth, 

 whence it arises that the cor- 

 tical substance easily breaks 

 up into the long fibres above 

 mentioned. The fibres them- 

 selves (which I should not be 

 inclined to consider as com- 

 pound elements of the cortical 

 substance, since their con- 

 stituents are separable, and 

 they themselves are far too 

 irregular), without constitu- 

 ting distinct lamellse, like the 

 plates of the nail and of the 

 epidermis, form a compact 

 fibrous bundle, and in this 

 manner the cortical substance, 

 which constitutes the princi- 

 pal bulk of the hair, is produced. 



The dark spots, dots, and streaks of the cortex, are very various 

 in their nature, and are principally : 1, granular pigment; 

 2, cavities filled with air or fluid ; and 3, nuclei. The action of 

 caustic potass and soda, which soften and swell up the cortical 

 substance without attacking the spots (fig. 67), shows that they 

 are in great measure nothing but aggregations of pigment 



Fig. 64. Plates or fibre-cells of the cortical substance of a hair treated with acetic 

 acid, x 350 : A, isolated plates, 1, from the surface (3 single, 2 united) ; 2, from the 

 side. B, a lamella composed of many such plates. 



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