LESSON 25.] 



THE NAILS. 



shown at a, the corium and lateral parts at , the stratum, first de- 

 scribed by Malpighi, and called by his name, with white ridges, at c 

 horny layer, on the wall of the nail, e; horny layer, or proper nail 

 substance, f with short notches upon its under surface, d. 



FIG. 110. 



Transverse section, through the body and bed of the Nail. 



414. The Malpighian layer of the nail, like that of the epider- 

 mis, consists wholly of nucleated cells, and agrees in all essential 

 points with it, except that the deep portion contains a series of large 

 perpendicular cells. In the negro, the Malpighian layer of the nail is 

 black, and its cells even appear to contain dark brown nuclei, as well 

 as yellowish brown ones in dark Europeans. An enlarged view of a 

 transverse section through the body of the nail (Fig. Ill), will better 

 explain these facts. A, represents the cutis (true skin) of the bed of 

 the nail ; B, Malpighian layer ; C, horny layer, or proper nail sub- 

 stance ; a, layers of the bed of the nail ; 5, white ridges of the 

 Malpighian layer; c, ridges of the horny 

 layer of the nail ; d, deepest perpendicular 

 cells of the Malpighian layer; e, its upper 

 series of flat cells ; /", nuclei of the horny 

 layer. 



415. The structure of the horny layer 

 can only be ascertained by the aid of re- 

 agents ; thus, boiled in dilute caustic soda, 

 it appears in the form of beautifully definite 



FIG. 112. 



FIG. 111. 



Transverse section through the 

 body of a Nail. 



Nail plates from the surface, boiled 

 in Caustic Soda. 



nucleated cells (Fig. 112); the distended membrane of the cells is 

 shown at a, and the nuclei at b. 



