106 HAIRS. [SECT. 58. 



body, so that even mummy hairs are found quite unaltered. By 

 metallic oxides, the hairs are coloured exactly like the epidermis ; 

 thus they are rendered black by the salts of silver aud man- 

 ganese, while sulphurets of these metals are formed; chlorine, 

 on the other hand, bleaches them. The ash amounts, on an 

 average, from 1 to 2 per cent., and contains oxide of iron (more 

 in dark hair), oxide of manganese and silica (traces); in white 

 hairs, phosphate of magnesia and sulphate of alumina (Jahn). 



§ 58. With reference to their finer structure, two substances 

 may, without exception, be distinguished in all hairs, and in many 

 even three : 1. the cortical substance (more properly, fi b rotis sub- 

 stance), which forms by far the most important part of the hair, 

 and gives it its shape ; 2. the cuticle, a delicate external covering 

 on the fibrous substance ; 3. the pith, or medullary substance, which 

 is situated in the centre, and is often wanting. 



The cortical, or fibrous substance, is longitudinally striped, very 

 often darkly punctuated, and streaked or speckled; and always 

 more or less intensely coloured, except in white hairs, in which it 

 is transparent. The colour is sometimes distributed pretty 

 uniformly through the whole substance, sometimes more concen- 

 trated in the form of elongated, granular spots. The more minute 

 structure of the fibrous substance of the hair, as well as the nature 

 of its spots and strise, can only be sufficiently elucidated by the 

 employment of acids and alkalies, usually much resorted to in the 

 investigation of the hair, and by other modes of procedure. If a 

 hair be treated with hot concentrated sulphuric acid, its fibrous 

 substance may be separated, much more easily than before, into 

 flat, long fibres of variable breadth (generally o'ooi"' to cvoc^'"), 

 which are distinguished especially by their stiffness and brittleness, 

 and their irregular, even jagged, borders and extremities. In light 

 hairs these fibres have a bright, in dark hairs a dark colour. These 

 so-called hair-fibres are, however, not the ultimate elements of the 

 cortical substance, but each of them must be regarded as an aggre- 

 gation of long, flat, nucleated fibre-cells or plates, which, after 

 thorough treatment with sulphuric acid, can be obtained isolated 

 along with the fibres. These, which may be best designated plates 

 of the fibrous substance, ox fibre-cells of the cortex, are fiat and, in 

 general, spindle-shaped, o - 024'" to o - o33'" long, o - oo2"' to 0'004"', 

 even o"005'" broad, o'ooi2'" to o*ooib"' thick, with uneven sur- 

 faces and irregular borders. They do not swell up into vesicles in 

 caustic alkalies, and often present in their interior a darker streak 



