OF THE NAILS. 



L57 



nail is of a tolerably uniform whitish colour, and transparent, 

 though somewhat whiter at the root than in the body. 



Fig. 61. 



§ 49. 



Structure of the Nail. — The nail consists in its deeper parts 

 of a soft, somewhat pale stratum mucosum, which is distin- 

 guished from the hard external horny layer, or proper nail, 

 still more sharply than 

 in the common cpider- j. 



mis. It covers the whole 

 of the lower surface of 

 the root and body of the 

 nail, frequently also a 

 small part of the upper 

 surface of the root, and 

 forms by itself the above- 

 mentioned laminse on the 

 under surface of the nail. 

 Its thickness at the pos- 

 terior part of the root 

 upon the under side mea- 

 sures 0-12'"; on the up- 



%. r 



a 



per, 0-14 '; close behind 



the margin of the root 



directly from behind forwards, 024 — 0-26'"; on the body of 



the nail on the laminae, more posteriorly and at the edge 



004— 0-05'"; in the middle 006'", even 0-08— -096'" and 



0-12'" ; between these, 0-032 — 004'". 



The Malpighian layer of the nail, like that of the epidermis, 

 consists wholly of nucleated cells, and agrees in all essential 

 points with it, except that the deep portion contains many layers 

 of elongated (of 0*004 — 0-007'") perpendicular cells, in conse- 

 quence of which a striated appearance is produced, which has 



Fig. 61. Transverse section through the body of the nail, x 250. A, cutis of the 

 bed of the nail ; B, mucous layer of the nail ; C, horny layer of it, or proper nail 

 substance : a, layers of the bed of the nail ; b, layers of the stratum Malpighii of the 

 nail ; c, ridges of the proper substance of the nail ; d, deepest perpendicular cells of 

 the mucous layer of the nail ; e, upper flat cells of it ; /, nuclei of the proper sub- 

 s tance of the nail. 



