128 TRANSACTIONS, NATURAL HISTORY SOCIETV OK GLASGOW. 



to the cuticle of the root-sheath. With this excep- 

 tion, the layers exactly correspond with those of 

 the root-sheath of the hair. The outer root-sheath 

 can be traced from the bottom of the follicle right 

 up to the Malpighian layer of the skin. The two 

 layers of the internal root-sheath can be traced 

 from their origin at the base of the follicle to about 

 three-quarters way up the follicle, where there is 

 what may be called the Sebaceous Recess. This 

 remarkable organ is formed by the root-sheath dilat- 

 ing and doubling on itself, forming a channel com- 

 pletely round the spine. The sebaceous matter is 

 collected in this from a series of simple glands in 

 which it is formed, and which open on the upper 

 surface of this encircling channel. As the mature 

 spine approaches the surface, the sebaceous glands 

 retain their position relatively to the skin, so that 

 they are frequently seen only a little way removed 

 from the base of the spine. In the mature spine, 

 however, the channel is closed and more or less 

 obliterated. 



The outer root-sheath measures on an average 

 about 4^^ of an inch in thickness, and is a direct 

 continuation of the cells from which the spine is 

 formed. It is a typical Malpighian layer, and is 

 made up of about four or five rows of cells. The 

 cells of the external row are somewhat cubical or 

 cylindrical ; the other cells are chiefly irregular poly- 

 hedra. The most internal, that is, those in contact 

 with Henle's layer, are usually flattened. The layer 

 is pretty uniform in thickness, except as it nears 

 the sebaceous recess, where it is as much as ^^ to 

 2^ of an inch. Between this and the skin it is 

 again thin, measuring only jj^ of an inch. 



With regard to Henle's layer, 1 am sorry my 

 observations are not perfectly conclusive as to its 

 origin. I have, however, certain preparations which 

 show an appearance almost exactly like that de- 

 scribed by Unna * in the root-sheath of the hair ; 



*Archiv. f. Mikroscop. Anat., Bd. xii., p. 0(55. 



