HAIR. 



[ 372 ] 



HAIR. 



principally owing. The pigment-granules 

 are exceedingly minute, about 1-50,000" in 

 diameter, rounded, and, as existing in the 

 hair, are mostly arranged in linear groups, 



Magnified 350 diameters. 



A, Portion of a white hair after treatment with soda, 

 a, nucleated cells of medulla, free from air ; b, cortical 

 substance with fibrillation and linear nuclei ; c, cuticle. 

 B, three isolated nuclei from the cortex. 



then* colour and number varying with that 

 of the hair. The pigment- granules are best 

 separated by the action of caustic potash or 

 soda, and they frequently exhibit molecular 

 motion. 



The striated and dotted appearance of the 

 shaft of hairs is not produced simply by the 

 nuclei, nor by the pigment, but arises in 

 part also from the unequal refraction of the 

 light by the various parts of the cells, and 

 from the presence of minute spaces filled 

 with air. The nature of each can always be 

 determined by attention to the principles 

 laid down in the INTRODUCTION. 



Towards the bulb, the cells of the cortex 

 are more distinct, less elongated, and, as well 

 as the nuclei, more easily isolated when 

 treated with acids (fig. 295), whilst in the 

 bulb itself they are round (fig. 296), 1-4000 

 to 1-1800" in diameter, closely crowded, 

 and sometimes containing only a colourless 

 nucleus, at others pigment-granules. 



The medulla, like the cortex, consists ot a 

 number of cells. Its structure is best ob - 

 served in a hair which has been treated with 

 soda or potash. The cells are then seen to 



Fig. 295. 



Fi*. 96. 



Magnified 350 diameters. 



Fig. 295. Two striated cells from the cortex of the root 



close above the bulb, with nuclei. 

 Fig. 296. Cells from the deepest portions of the bulb ; 



a, from a coloured bulb, with pigment-granules and 



partly concealed nuclei ; 6, from a white hair, with 



distinct nuclei and a few granules. 



be arranged in one or more linear series 

 (fig. 294 a) ; they are angular or rounded, 

 1-2000 to 1-1000" in diameter; and if the 

 action of the alkali has not been too long 

 continued, they exhibit a nucleus ; they fre- 

 quently also contain one or more granules or 

 globules of fat (fig. 297). In the shaft and 



Fig. 297. 



Magnified 360 diameters. 



Medullary cells with pale nuclei and fatty granules, 

 from a hair treated with soda. 



upper part of the root of the hair, these 

 cells contain air, which gives them a dark or 

 black appearance by transmitted lio-ht \ and 

 it was the generally received opinion, until 

 we pointed out the error several years ago, 

 that this darkness or blackness arose from 

 the presence of pigment. The contrary, 

 however, may be easily proved by mace- 

 rating the hair in oil of turpentine or any 

 liquid, when the air escapes in bubbles and 

 becomes displaced by the liquid ; moreover, 

 on drying the hair, the air and black ap- 

 pearance return. PI. 29. fig. 1 represents a 

 white hair;, in which the medullary cells of 



