STRUCTURE OF THE NAILS. 259 



"We must hence, in considering the nails, regard (1) the nail 

 itself ; (2) the portion of the skin covered by the nail or bed of 

 the nail ; and (3) the wall of skin that includes three sides of 

 the nail or groove for the nail. 



The nail itself presents an anterior free border, a posterior 

 and two lateral borders that lie in the groove for the nail ; a 

 convex upper surface, that for the greatest portion of its extent 

 is free, and an inferior surface attached to the bed of the nail. 



The posterior part which is imbedded in the groove is the 

 root of the nail, and the rest constitutes the body. 



The surface of the skin covered by the nail, or nail bed, is 

 divisible into a posterior part, or matrix unguis, covered by the 

 root of the nail ; and an anterior part, the proper bed of the nail. 

 The skin bounding the posterior and lateral borders of the nail 

 forms a wall, the nail wall, that is thickest posteriorly, becomes 

 thinner anteriorly, and forms with the nail bed the so-called 

 nail fold or groove (Nagelfalz). 



The nail bed passes anteriorly into the skin of the ball of the 

 finger, and posteriorly and laterally into the inferior surface of 

 the nail wall, which is turned towards the nail. It consists of 

 subcutaneous connective tissue, corium, and rete mucosum. 



The subcutaneous connective tissue of the nail bed is charac- 

 terized by the absence of fat, and by the course of the ascending 

 connective-tissue fibres which arise as separate fasciculi from 

 the periosteum of the last phalanges, expand above in a 

 brush-like manner, and are directed somewhat backwards 

 towards the root of the nail. Between the several fasciculi 

 are spaces filled with loose connective tissue, or frequently by 

 a few fat cells, and they also enclose numerous vascular loops. 



The course of the fasciculi of connective tissue in the corium 

 of the bed of the nail resembles that of other parts of the skin, 

 except in the unusual number of the fibres ascending from the 

 subcutaneous cellular tissue, which are elsewhere rare as com- 

 pared with the horizontal bundles. 



The nature of the surface of the corium of the bed of the 

 nail constitutes, however, its most characteristic feature, though 

 its posterior part, which we have termed matrix unguis, presents 

 some differences from the anterior part, or proper nail bed. The 

 surface of the matrix of the nail, which lies on a somewhat 



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