OF THE HAIRS. 



17T 



The color of the cortical substance arises partly from spots of pio-ment, 

 to some extent from air cavities, and partly from a coloring matter dif- 

 fused through and combined with the substance of the cortical plates. 

 The first or the granular pigment, exhibits all shades from clear yellow, 

 through red and brown, to black; the diffused pigment is quite absent in 

 white hairs, and is scanty in clear, fair hairs ; it is most abundant in the 

 more opaque fair hairs, and in red as well as in dark hairs, in which it 

 may by itself give rise to an intense red or brown color. The color of 

 the cortex depends especially upon that of these two pigments, but 

 sometimes the one, sometimes the other predominates, and it is only in 

 the very light and in the very dark hairs that they are developed in about 

 equal proportions. 



Fig. 68. 



§ 57. The medullary substance is a streak or cord which extends in 

 the axis of the hair, from the 

 neighborhood of the bulb 

 nearly to the point (Figs. 65, 

 68). It is generally absent 

 in the lanugo and colored 

 hairs of the head, but is 

 usually present in the thick, 

 short hairs, and in the 

 stronger long ones, as well 

 as in the white hairs of the 

 head. If white hairs be 

 boiled with caustic soda until 

 they swell and coil up, we 

 can often, by the use of jii 

 simple pressure, demonstrate ' 

 without further trouble, the 

 cellular structure of the 

 medullary cylinder, which is 

 then transparent for trans- 



FiQ. 68. — A portion of tlie root of a dark hair slightly acted upon by caustic soda; a, 

 medulla, su\[ containing air, and with ceils, which appear pretty distinct; b, cortex with 

 pigment spots; r, inner layer of the epidermis; rf, outer layer of it ; e, inner layer of the inner 

 root-sheath (^Huxley's layer) ;/, outer fenestrated layer (Hetile's layer). Magnified 250 diameters. 



of the hair is composed of superimposed laminae, and recommends, in order to demonstrate 

 the fact, that a hair should be treated with a solution of caustic potass of 10 per cent., and 

 then submitted to pressure. Under these circumstances, " beautiful lamella; appear. The 

 separate layers exhibit no trace of being composed of fusiform cells; they appear finely 

 striated, and in places, hyaline; sometimes elongated spots appear, of which it cannot be 

 determined with certainty whether they are nuclei or i)erforations in the membrane." In 

 some, there was no trace of these to be seen. Reichert considers the fibres of the cortex to 

 be artificial products, and was unable to convince himself of the existence of nuclei in this 

 part of the hair. — Tks.] 



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