THE APPENDAGES OF THE SKIN 



1159 



upon the surface of the true skin, as the epidermis is in other parts. The part 

 of the cuti.s beneath the body and root of the nail is called the matrix (matrix 

 iiHf/itiff), because it is the part from which the nail is produced. Corresponding 

 to the body of the nail, the matrix is thick, and raised into a series of longitudinal 

 ridges (crixtae matricis unguis), which are very vascular, and the color is seen 

 through the transparent tissue. Behind this, near the root of the nail, the papilhe 

 are small, less vascular, and have no regular arrangement, and here the tissue 



Stratum M<iJ 



iVrti/ grooi 



onnm. 



liiml- vessel. 



FIG. 872. Transverse section through human n; 



(From Bohm and Davidoff's Histology.) 



of the nail is somewhat more opaque; hence this portion is of a whiter color, 

 and is called the lunula on account of its crescentic shape. 



The cuticle, as it passes forward on the dorsal surface of the finger or toe, is 

 attached to the surface of the nail, a little in advance of the nail root; at the 

 extremity of the finger it is connected with the under surface of the nail a little 

 behind its free edge. The cuticle and the horny substance of the nail (both epi- 

 dermic structures) are thus directly continuous with each other. The nails con- 

 sist of a greatly thickened stratum lucidum, the stratum corneum forming merely 



HORNY 

 LAYER 



RIDGES OF 

 MATRIxVy 



NAIL WALL 



MALPIGHiAN 

 LAYER 



SULCUS OF 



MATRIX 



LATERAL 

 MARGIN 



RETINACULA^.- 

 OF SKIN 



RIDGES^-; 

 OF SKIN 



PALMAR SURFACE 

 OF FINGER 



FIG. 873. Tran.sverse section through the nail and the terminal portion of the ring finger. (Toldt.) 



the thin cuticular fold (eponychium) which overlaps the lunula. The cells have 

 a laminated arrangement, and are essentially similar to those composing the 

 epidermis. The deepest layer of cells, which lie in contact with the papillae 

 of the matrix, are columnar in form and arranged perpendicularly to the surface; 

 those which succeed them are of a rounded or polygonal form, the more superficial 

 ones becoming broad, thin, and flattened, and so closely compacted as to make the 

 limits of each cell very indistinct. It is by the successive growth of new cells at 

 the root and under surface of the body of the nail that it advances forward and 





