440 THE NAILS. 



a modification of albumen ; and thus resemble cuticle and horn 

 in their composition. 



The growth of the nails, forwards, is entirely from a fold 

 of the cutis vera, at its root, called, though not with exact pro- 



priety, the matrix of the nail, as seen 

 iri fig. 116. It grows also in thickness 

 %>m the upper surface of the skin, 

 upon which the nail rests. In the 

 formation of a new nail the la- 

 men which starts from the matrix, 

 receives successive layers from be- 

 neath, as it approaches the extremity, the deepest seated of 

 which is the shortest. In this way the nail gets its thickness and 

 strength, and occasionally, where the deposition of new matter, 

 goes on more rapidly under the body of the nail than at the 

 matrix, the body is thrown up into unsightly rugosities. Its 

 development is exactly similar to that of the horns and hoofs of 

 animals. The striated appearances of the nail, is said to be 

 owing to the papillary prominences below, being arranged in con- 

 centric plicae. The white semicircular line at the root, is 

 called the lunula. 



The nails are not exactly analogous in structure to the cuticle, 

 in the ordinary acceptation of the term to that part which is 

 raised up under a blister. The proper cuticle is that thin coating 

 which is scraped away and worn off near the root, and which 

 otherwise would cover the surface. . The nails consist of the 

 proper cuticle, and tunica albuginea superficialis and the gem- 

 mules of Gaultier leaving interposed between them and the 

 cutis vera, the tunica albuginea profunda which is insensible, and 

 explains why it is that a splinter, or the blade of a small pair 

 of scissors, in the operation for onychia, may be run along 

 close on the under surface of the nail, without the production 

 of much pain. According to Breschet, the nail is formed like 

 the other parts of the horny coat exterior to the cutis vera, by 

 the glands for the secretion of the mucous and coloring matter ; 

 the products of which would be mixed up together, coloring the 

 substance of the nail, as we know is the case in regard to the 

 horns and hoofs of animals. 



