1294 THE SKIN, MAMMARY GLANDS AND DUCTLESS GLANDS 



tal free border [margo liber], which overhangs the tips of the fingers, an irregular, 

 sharp proximal edge [margo occultus], and on each side a somewhat thinned 

 border [margo lateralis] (fig. 1053). 



Fig. 1053. — Dorsal Surface of Isolated Finger Nail. (XI. 



Margo liber 



(FromToldt's Atlas.) 



Corpus unguis ^ 

 Margo lateralis - 

 Radix unguis ...^vji^f,'] 



- Margo lateralis 



- Lunula 



Margo occultus 



Each nail is composed of an exposed distal part, the body [corpus unguis], 

 and a proximal covered part, the root [radix unguis], (fig. 1053), which ends in 

 the margo occultus. The nail is at a slightly deeper level than the surrounding 

 skin which overhangs the root and the lateral margins in a fold, the nail wall 



Fig. 1054. — Finger Nail and Nail Bed. 



Corpus unguis 



Margo lateralis 



Lunula 

 Vallum unguis 

 Radix unguis 



Margo liber 

 Matrix unguis 

 Cristae matricis unguis 



Sulci matricis unguis 

 Margo occultus 



[vallum unguis] (figs. 1054, 1055, 1056). The epidermis of the free edge of the 

 nail wall, especially proximally, is thickened and often appears as a ragged edge. 

 At a deeper level than the above and extending somewhat more distally is a vari- 

 ably developed thin parchment-like membrane, the eponychium, closely attached to 



Fig. 1055. — Longitudin.\l Section Through the Tip of the Middle Finger. ( X 2) 



(From Toldt's Atlas.) 

 Stratum corneum 



Stratum germinativum / ^^'^o liber 



\.-'"r:^\ 



Corpus papillarcv ^ -flfe»v;-c^>* > \ i 



\'" j.a^ "IJL ^(\ Stratum corneum 



Phalanx lU 



V 



IK 



? J / stratum germinativum 



%y'!^.. , 5 ;V Matrix unguis 



'' I; 



Radix unguis 



the superficial surface of the nail. It is the representative of the superficial layers 

 of the embryonic epidermis wliicli do not take part in the formation of the nail. 

 The groove which is formed l)otw('eu the vallum and the underlying nail bed is 

 known as the sulcus matricis unguis. This lodges the root and lateral margins 



