154 SPECIAL HISTOLOGY. 



That part of the coriitm upon which the nail lies, or the bed 

 of the nail, corresponds exactly in form with it, is elongated, 

 quadrangular, arched in the middle, shelving off anteriorly 

 and posteriorly, and especially on the sides. When the nail 

 is removed by maceration in connection with the epidermis, its 

 anterior and middle parts are uncovered, whilst its lateral edges 

 and its posterior segment, on the other hand, are invested by 

 a process of the cutis, the wall of the nail, which is anteriorly 

 depressed and rounded off, posteriorly more acute and longer, 

 and, taken together with the bed, forms a fold, the fold of the 

 nail, which receives the lateral edges and the posterior (2 — 3"') 

 portion of its root (figs. 58, 60). 



Fig. 58. 



L^tWUf 



The bed of the nail presents upon its surface peculiar ridges, 

 similar to those of the palm and of the sole of the foot 

 (fig. 58 a). They begin at the bottom of the fold of the nail, 

 at the posterior border of its bed, and, as Henle (p. 270) 

 justly remarks, they run from the middle of it almost as from 

 a pole. The middle ones pass directly forwards ; the lateral 

 at first describe an arc, which is the more convex the further 

 out the ridges lie, and eventually are directed forwards like the 

 others. At a distance of 2\ — 3±'" from their origin, they all at 

 once become more prominent, and take on the form of true 

 lamina, of 0024 — O'l" in depth, which run directly, almost to 

 the anterior edge of the bed of the nail, and then end suddenly, 

 as if truncated. The line of transition of the ridges into the 

 lamina is convex anteriorly, and divides the bed of the nail 

 into two sections, differing both in their extent and in their 

 colour : the posterior smaller one is nearly covered by the 



Fig. 58. Transverse section through the body and bed of the nail, x 8 : a, bed of 

 the nail, with its ridges (black) ; b, corium of the lateral parts of the wall of the nail ; 

 c, stratum Malpighii of the nail with its ridges (white) ; e, horny layer on the wall 

 of the nail ; /, horny layer of the nail, or proper nail substance, with short notches 

 upon its under surface. 



