NAILS. 



63 



Very much the same is the case with the nails. Or 

 examining the section of a nail, made transversely to the 

 long axis of the finger, we see virtually the same struc- 

 ture as in ordinary skin, only every single indentation of 

 the inferior surface does not correspond to a conical 

 prolongation of the cutis, or papilla, but to a ridge which 

 runs along the entire length of the bed of the nail, and 

 may be compared with the ridges which are to be seen 

 upon the palmar surface of the fingers. Upon these 

 ridges of the bed of the nail are dwarfish, stunted papillae, 

 and upon them rests the rather cylindrically shaped 

 youngest layer of the rete Malpighii ; then follow cells 

 continually increasing in size, until at last the really 

 hard substance comes, which corresponds to the epi- 

 dermis. 



Nevertheless to discuss the subject at once, seeing 

 that I shall not again have occasion to mention it the 

 structure of the nails has been difficult to make out, 

 because they were conceived to be a simple formation. 

 Nearly all the discussions, therefore, which have taken 

 place, have turned upon the question where the matrix 

 of the nail was, and whether the growth of the latter 

 took place from the whole surface or from the little fold 

 into which it is received behind. If we consider the nail 

 with respect to its proper firm substance, its compact 

 body (Nagelblatt), this only grows from behind, and is 

 pushed forwards over the surface of the so-called bed of 

 the nail (Nagelbett), but this in its turn also produces a 

 definite quantity of cellular elements, which are to be 

 regarded as the equivalents of an epidermic layer. On 

 making a section through the middle of a nail, we come, 

 most externally, to the layer of nail which has grown 

 from behind, next to the substance which has been 

 eecreted by the bed of the nail, then to the rete Malpi- 

 ghii, and lastly to the ridges upon which the nail rests. 



