228 NORMAL HISTOLOGY. 



matrix of the nail. The corium of the nail does 

 not differ essentially from that of the skin in gen- 

 eral ; it is intimately connected with the periosteum 

 of the phalanx, and presents longitudinal ridges, 

 low in the matrix, higher in the nail-bed, which are 

 covered with papillae. The latter are bent obliquely 

 forward, and are more abundant in the nail-bed 

 than in the matrix. Upon and between the papillae 

 several layers of variously shaped cells lie, corre- 

 sponding to the Malpighian layer of the skin. In 

 the body these cells pass quite abruptly into the flat, 

 horny, nucleated cells of the hard substance of the 

 nail ; in the matrix, however, the transition is very 

 gradual, and it is here that the growth of the nail 

 occurs. The lunula is a portion of the nail in which 

 the Malpighian layer is very thick, as it is in all parts 

 of the root, and being evenly distributed over the 

 surface of the papillae, does not permit the color of 

 the blood in the capillaries of the papillae to be 

 seen, as it is in the rest of the nail-bed, where the 

 longitudinal ridges are higher, and covered by fewer 

 cells. 



THE HAIR. 



We distinguish in the hair : the shaft y which pro- 

 jects above the surface of the skin ; the root, which 

 is imbedded in an oblique tubular depression, called 

 the follicle ; and the bulb, a dilated portion at the 

 bottom of the follicles in which the hair ends. The 



