350 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



lateral margins are also covered by a fold of the skin 

 called the nail wall. The nails have a pink color 

 imparted by the subjacent blood, excepting near the 

 root, where there is an opaque area called the lunula. 

 The lunulae diminish in size from the thumb to the 

 little finger. 



Each nail rests upon a very vascular dermis which 

 has been called the nail bed 

 or matrix. This connective- 

 tissue bed has many fine 

 longitudinal ridges and 

 alternating grooves which 

 fit closely into correspond- 

 ing grooves and ridges on 

 the lower surface of the 



nail. Each nail consists of two parts: a deep soft 

 stratum that represents the Malpighian layer of the 

 epidermis, and an external hard cornified layer that 



Body of nail. 



Fig. 246. Thumb nail. 



Body of nail. 



Root of nail. 



Mantle. 



Phalanx. 



Nail bed. 

 Fig. 247. Longitudinal section of nail. 



represents the horny layer. The former consists of 

 nucleated polygonal prickle cells which fill the fur- 

 rows and cover the nail bed several cells deep. It is 

 affirmed that the cells of this Malpighian layer, in 

 the distal part of the nail, do not produce any of the 

 overlying horny material, but that growth of the nail 



