THE ROOT-SHKATH IN HEDGKH06-SPINES. 129 



and I think one is entitled to infer that the cells of 

 Henle's layer are formed from a row of cells which 

 originate at the base of the follicle. Hitherto the 

 cells of Henle's layer have been invariably described 

 as non-nucleated, but in the Hedgehog there may 

 be easily seen ^vell marked elongated nuclei which 

 take on a fairly deep stain with hsematoxylin. 

 These nviclei can only be seen in the lower half of 

 the follicle, and only in young spines. The cells are 

 irregularly cylindrical in shape. I have not been 

 able to make out from sections the fenestrse usually 

 described in Henle's layer, but which Kolliker regards 

 as probably due to the preparation. As in other 

 animals, there is only a single row of cells. It is 

 here thickest at its lower end, and, gradually thinning 

 away, ends at the sebaceous recess. When the 

 spine becomes nearly full grown this layer becomes 

 broken up, and we find merely a number of irregu- 

 lar shrivelled cells lying between the outer root- 

 sheath and Huxley's layer. 



Huxley's layer is much better developed in the 

 spine than in the hair. It arises with the spine 

 from the base of the foUicle, and is in reality a 

 part of the spine in which the cells do not undergo 

 a horny transformation. It usually consists of about 

 three or four rows of elongated flattened nucleated 

 cells. The cells are somewhat pointed at the ends 

 and are more or less granular. Besides these 

 ordinary cells, there are frequently seen, either 

 singly or in small grovips, much larger and highly 

 refracting cells, which are possibly the same as Lwoff * 

 found by teasing. They are oval in shape and have 

 each a shrivelled nucleus. Huxley's layer gradually 

 thins away as it approaches the sebaceous recess, 

 where it ends abruptly. That Huxley's layer is 

 carried up with the spine there cannot be the 

 slightest doubt. In some of my sections the edges 

 of the cells of the internal row are seen fitting 

 accurately into the notches on the surface of the 

 spine. 



*Bull. Soc. Imp. Mosc, T. lix. (1884), p. 156. 



