2 HITHERTO UNDESCRIBED STRUCTURE IN HUMAN HAIK 



Perhaps some light may be thrown upon the contradictory 

 opinions here set forth, by some observations made by myself in 

 the beginning of the present year, and since repeated so frequently, 

 as, I hope, to avoid all source of error. 



If the sheath of the root be split longitudinally with needles or a 

 fine knife — removed, and laid out flat with the inner surface upper- 

 most, the fenestrated membrane will be at once seen, when the focus 

 of the microscope is adjusted to its upper surface. If some part 

 where the sharp well-defined edge of this membrane is free, be now 



Fig I. 



more carefully examined there will probably be seen extending for 

 some little distance beyond, and lying above it, a single layer of'Very 

 pale epithelium-like nucleated cells. If the eye be now carried again 

 over the fenestrated membrane (the focus being carefully adjusted), 

 this layer will be found to be" traceable over the fenestrated membrane,, 

 and to be in close connection with it. 



The individual cells composing the layer are very delicate and 

 pale, readily escaping observation when not separated from the other 

 structures ; they are more or less polygonal or rounded, i-6ooth ta 



