60 THE HAIR. 



for instance, sulphuric acid, or caustic potash or soda. This 

 scaly covering of the hair is not itself affected by such reagents, 

 but by friction individual scales may be isolated, which then appear 

 extremely transparent and quadrangular, and are devoid of nucleus 

 or other contents, although they are generated from perfectly nor- 

 mal cells, as is seen by examining the root of the hair. Kolliker* 

 draws attention to the fact that these epithelial scales on the hair 

 differ from the other elements of the hair, and from all the consti- 

 tuents of other horny tissues, by their perfect insolubility in 

 alkalies and concentrated sulphuric acid. We do not, however, 

 agree with the supposition of Donders,t based on this mechanical 

 relation, that these scales consist of a protein-compound. 



The cortical or fibrous substance, constitutes, as is well known, 

 the principal part of the hair. By the use of the reagents above 

 referred to, namely concentrated and gently heated sulphuric acid, 

 this substance separates into flat, long fibres, which again divide 

 into long, very narrow plates, having a dark, elongated nucleus. 

 After prolonged digestion with a dilute solution of potash, the 

 cortical substance dissolves, with the exception of these long, 

 spindle-shaped nuclei. Even if these plates did not so plainly 

 bear the stamp of cell- formation, they would readily be recognised 

 as cells by examining the corresponding part of the root of the 

 hair. These plates gradually shorten, and the elongated nuclei 

 become thicker towards the root of the hair, and at length, in the 

 lower part of the root, we find oval or roundish cells with oval 

 nuclei. 



Kolliker's observations show that here also the chemical meta- 

 morphosis corresponds with the change of form, and that the cells 

 of the cortical substance in the lower part of the root of the hair 

 are not merely more easily affected by alkalies and concentrated 

 sulphuric acid than the fibre-cells of the same substance, but that 

 they become swollen, and are in part dissolved even by acetic 

 acid, which produces no effect on the other cells. According to 

 Kolliker, there are within the fibrous substance certain cavities 

 filled with air, and also accumulations of pigment-granules, the 

 quantity of which varies with the colour of the hair. 



The inner portion of the hair is composed of the medullary 

 substance, the nature of which cannot be recognised distinctly 

 until the cortex has been rendered transparent by the action of 

 alkalies. It consists of closely arranged rows of quadrangular, or 



* Mikrosk. Anat. Bd. 2, S. 122. 



t Vers. einer physiol. Chem. S. 572 [or English Transl p 523]. . 



