OF THE NAILS. 



159 



Haut," 1848); and Kramer ("Ueber Condjlome u. Warzen," Getting. 

 1847). [Meissner, " Beitrage zur Anatoniie und Pliysiologie der Ilaut ;" 

 Leipzig, 1853.] Figures are given by R. Wagner, " Icon. pbys. ;" Ber- 

 res, tab. vi. vii. xxiv. (middling, witb tbe exception of what regards the 

 vessels); Arnold, " Icones org. sens.," tab. xi. (very pretty, but drawn 

 with too low magnifying powers) ; Hassall, tab. xxiv. xxvi. xxvii. (among 

 others, the skin of the negro also, and the areola of the wliite from 

 within, colored); and myself, "Mikr. Anatomie," Taf. i. 



II. — OF TDE NAILS. 



§ 48. The vails, tmgucs, are nothing but peciiUarJ^ metamorpliosed 

 parts of the epidermis, and like it they consist of two layers, — of a soft 

 mucous, and a horny layer, or tlie pro~per nail. 



That part of the corium 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 espe- 

 cially on the sides. When the nail is removed by maceration in con- 

 nection 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 lines) portion of 

 its root (Figs. 58, 60). 



Tm. 58. 



..-r 



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 mid- 

 dle of it almost as from a pole. The middle ones pass directly for- 

 wards ; the lateral at first describe an arc, which is the more convex 



Fig. 5S. — Transverse section through the body and bed of the nail, a, bed of the nail, 

 with its ridges (black) ; 6, corium of the lateral parts of the wall of the nail; c, straUmi Mai- 

 pighii of the nail with its ridges (white) ; c, horny layer on the wall of the nail ;/, horny layer 

 of the nail, or proper nail substance, with short notches upon its under surface.— Magnified 

 8 diameters. 



