260 SKIN, HAIR, AND NAILS, BY ALFRED BIESIADECKI. 



lower plane than the nail bed, is covered with papillse directed 

 forward (Henle), and implanted on low mound-like elevations of 

 the corium. The height of the papillse varies from O'l to 0'2 

 of a millimeter, and their breadth from O'OS to 0*06 of a milli- 

 meter. At an arched line parallel with the tip of the finger, and 

 usually covered by the nail wall, the surface of the proper 

 nail bed is covered with from fifty to ninety ribs, having a height 

 of from O'l to 0'2 of a millimeter. These ribs, which are prolon- 

 gations of the mound-like elevations of the matrix, increase in 

 height towards the free border of the nail, and are continuous 

 below the free edge with papillse, having a diameter of as much 

 even as 0'5 of a millimeter. The ridges are chiefly composed of 

 vertical and parallel fibres of connective tissue, between which 

 numerous fusiform cells are imbedded. 



The bloodvessels of the bed of the nail form a coarse plexus 

 in the corium of the matrix, from which vascular loops are 

 given off to the papillse ; on the other hand, the proper bed of 

 the nail has a much finer plexus, from which numerous thick 

 vascular loops ascend into the ridges. 



Numerous medullated nerve fibres lie in the subcutaneous 

 tissue of the nail bed, and, losing their medullary sheath at 

 about the level of the corium, run vertically to the surface. In 

 one specimen prepared with chloride of gold, I followed such a 

 nerve fibre as far as to the surface of the corium, from which 

 the mucous layer had been detached in the act of preparation; 

 I was unable to find any nerve fibres in the latter. 



The upper surface of the dorsum of the wall of the nail is 

 similar to that of the skin of the corium of the fingers; whilst 

 its lower surface, that is turned towards the nail, is destitute of 

 papillse, is smooth, and contains no glands. 



The rete mucosum, or mucous layer of the nail bed, differs 

 in no respect from that of other parts of the skin. It fills up 

 all the depressions of the nail bed, and the valleculse between 

 the papillse of the matrix, as well as the furrows between the 

 ridges, and is immediately continuous with the mucous layer 

 of the adjoining skin, and with that of the nail fold. At the 

 posterior angle of the nail fold the mucous layer of the nail 

 matrix so fuses with that of the nail wall, as to form a wedge- 

 shaped portion, which projects from the angle of the fold into 



