174 



SPECIAL HISTOLOGY. 



of the hairs in general) and other manipulations. If a hair be treated 

 with concentrated sulphuric acid at a warm temperature, its fibrous 

 substance is much more readily broken up than before, into flat elon- 

 gated fibres of various breadths (commonly '002-0 '005 of a line), which 

 are characterized particularly by their rigidity and brittleness, and by 

 their irregular, even notched, margins and ends : in pale hairs they are 

 clear, and in dark ones have a dark tinge. These so-called hair-fibres 

 Fig. 64. are not, however, the ultimate ele- 



ments of the fibrous substance ; each 

 of them, in fact, consisting of an 

 aggregation of flat, moderately-long 

 fibre-cells or plates, which may be 

 found isolated among the fibres after 

 the thorough action of sulphuric acid. 

 These (Fig.- 64), which may best be 

 named the plates of the fibrous sub- 

 stance, or ihe fibre- cells of the cortex, 

 are flat and generally fusiform, 0-024 

 -0-033 of a line long, 0-002-0-004, 

 or even 0-005 of a line broad, 0-0012 

 -0-0016 of a line thick, with uneven 

 surfaces and irregular edges ; they 

 do not swell up into vesicles on the 

 addition of caustic alkalies, and they 

 very frequently exhibit a darker 

 streak in their interior, of which we 

 shall speak immediately ; under cer- 

 tain circumstances they also contain 

 granular pigment; for the rest they 

 are homogeneous, and present no 

 minuter elements, such as fibrillse or 

 the like. They appear to be more 

 strongly united longitudinally, than 

 in the direction of their breadth, 

 whence it arises that the cortical sub- 

 stance easily breaks up into the long 

 fibres above mentioned. The fibres themselves (which I should not be 

 inclined to consider as compound elements of the cortical substance, 

 since their constituents are separable, and they themselves are far too 

 irregular), without constituting distinct lamellae, like the plates of the 

 nail and of the epidermis, form a compact fibrous bundle, and in this 



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

 magnified 350 diameters : ./#, isolated plates, 1, from the surface (3 single, 2 united) ; 2, from 

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



