DEVELOPMENT OF THE NAILS. 263 



Inflammation of the matrix, attended with suppuration, 

 leads to temporary or permanent loss of the nail, according 

 to whether it is reproduced or altogether destroyed. 



The new nail is formed by the matrix, and grows from 

 behind forward over the nail bed. Suppurative inflammation 

 of the proper bed of the nail causes no disturbance of the growth 

 of the nail, and although it is frequently not again applied 

 to the bed, it yet continues to maintain its normal thickness. 



The nail itself, which is homogeneous in transverse section, 

 or at most exhibits fine strise, and refracts light doubly, is 

 composed of nucleated epidermal scales intimately cemented to- 

 gether, but capable of being broken up by the action of various 

 chemical agents. 



According to Moleschott, ammonia dissolves the sparing 

 amount of cement present in the nail cells in twenty-four hours. 

 The cells form irregular polyhedra, and each includes a single 

 round nucleus. Ammoniated oxide of copper in strong solution 

 converts the scales into polyhedra in the course of an hour and 

 a half, and in two or three hours they swell up to elliptical 

 vesicles. These solutions rapidly attack the nuclei. 



The best means of obtaining separate nail cells with distinct 

 nuclei, is to macerate the nail for three or five hours in a 27 

 per cent, solution of potash. The nail soon becomes very soft, 

 and it is only requisite to spread out a thin layer on the glass 

 to obtain a satisfactory specimen. 



The nail is finely and longitudinally striated, its surface 

 exhibiting ribs that are not to be regarded as the expressions 

 of the ridges of the nail bed (Kolliker), but as the result of the 

 papillary structure of the matrix of the nail (Henle), since the 

 nail root is also ribbed. 



DEVELOPMENT OF THE NAIL. At the third month of foetal 

 life we may observe a mound-like elevation of the skin, con- 

 cave anteriorly, on the last phalanges, which corresponds to 

 the nail fold, and results from the circumstance that at a line 

 corresponding to the concavity of this elevation the mucous 

 layer sends a wedge-like process into the tissue of the corium. 

 This process consists of from two to three tiers of epithelial 

 cells resembling those of the mucous layer. 



