THE SKIN. 



577 



of fat-globules, and blending with the periosteum of the last 

 phalanx. In this situation the vascular supply is strikingly 

 large. (See Fig. 243.) 



i 



FIG. 243. NAIL OF FINGER, VERTICAL SECTION, RECTANGULAR 



TO THE LONG AXIS OF THE FlNGER. 



P, papilla? with blood-vessels ; B, rete mucosum ; N, horny epidermal scales. Magnified 

 100 diameters. 



The derma is covered by an epithelial layer, identical with 

 that of the rete mucosum, and filling the valleys between the 

 papillas in such a manner that the upper boundary of the rete 

 mucosum exhibits only a fluted contour. According to C. Toldt, 

 the so-called lunula of the nail, most distinctly marked on the 

 nail of the thumb, is caused by a lessened transparency of the 

 nail, due to the rete mucosum producing, in this situation, a 

 broad layer of a uniform distribution. The rows of the papillae 

 are much less developed in the region of the lunula than in the 

 rest of the matrix. By scraping with the knife the lower surface 

 of the detached nail, the lunula disappears, and the nail becomes 

 uniformly transparent. 



The nail substance consists of horny epithelia, of which the 

 lower ones exhibit indistinct nuclei, while the outermost resem- 

 ble epidermal scales. In the region of the root a gradual tran- 

 37 



