568 BALDWIN SPENOER AND GEORGINA SWEET. 



there lies a single layer of flattened, deeply-stained nuclei, 

 which, by the way in which they take the stain^ can always be 

 distinguished from those lying to the outside. These nuclei 

 become more rounded as they are traced lower down in the 

 bulb, and in this part the layer in which they lie can sometimes, 

 as shown in the figure, be seen to be marked off by a more or 

 less clear line from those of the inner root-sheath. In the 

 region of the bulb the inner root-sheath is clearly distinguish- 

 able into an inner and an outer part, which, however, merge 

 into one another at the level at which the hair is constricted. 

 The outer layer has undergone cornification, while the inner 

 one stains more deeply with the haemalum ; its nuclei are 

 clearly visible, and below it melts into the more or less undif- 

 ferentiated part which forms the rim of the bulb. Above the 

 level at which the hair is constricted, that is slightly above 

 that of the tip of the papilla, there is no differentiation of the 

 inner root-sheath into the equivalents of Huxley's and Henle's 

 layers. Outside the inner root-sheath, and in this part 

 sharply marked off from it (fig. 24) lies the outer root-sheath, 

 in which, in comparison with earlier stages, a considerable 

 proliferation of nuclei has taken place, the outer layer being 

 set with their long axes at right angles to that of the follicle. 

 A transverse section (fig. 26) shows clearly the relative size of 

 the various layers as they are seen when the hair at this stage 

 is cut across in its follicle. The whole hair is filled with pig- 

 ment, there is no clearly marked medulla, and the groundwork 

 of the whole structure is evidently, from the way in which the 

 stain is taken, of a corneous nature. The cuticle is sharply 

 outlined, and is closely invested by the thick inner root-sheath, 

 which has the form of a network, the nuclei having by this 

 stage completely disappeared, the part next to the cuticle 

 being more cornitied than that on the outside. In somewhat 

 younger stages in which the hair is not so large (fig. 23) the 

 gradual cornification of the root-sheath can be well seen. 

 Here, next to the cuticle, the nuclei have disappeared, while 

 outside this they are evidently undergoing change prior to 

 complete degeneration. 



