416 INNERVATION. [CHAP. xiv. 



pregnancy, or of accidental moles, or freckles.* The bronzing of 

 parts exposed to the sun is effected by a similar deposit of colouring 

 matter in the deeper laminse of the cuticle. 



The subject here referred to has been invested with additional 

 interest by its supposed bearing on the warmly-debated question of 

 the specific difference of the negro from the white man. We need 

 not enquire how far the existence of a distinct cuticular lamina 

 might avail the advocates of such a difference, for we may freely 

 state our conviction that no such peculiar layer exists. The sole 

 variety is in the presence of pigment which may occur, partially, 

 under many circumstances in the white races, and may be wanting 

 in the true negro. t The reader of the preceding paragraphs will 

 understand how little such processes as maceration, and even the 

 most delicate dissection by the naked eye, and with ordinary in- 

 struments, are to be depended on for the determination simply of 

 the anatomical fact. 



The nails and hairs are peculiar modifications of the epidermis, 

 and consist essentially of nucleated particles. 



The nails are flattened, elastic, 

 horny, protective coverings, placed on 

 the dorsal surface of the terminal 

 phalanges of the hands and feet, and 

 projecting beyond the flesh. Hoofs, 

 claws, etc., are varieties of them. 

 The nail has a root, or part concealed 

 within a fold of the cutis; a body, or 

 exposed part, attached to the surface 

 of the cutis ; and a free or projecting 

 section of the skin on the end of the e dqe. The cutis underneath the root 



finger -.The cuticle and nail, n, detached * 



from the cutis and matrix, m. anc i "body is termed the matrix, from 



its being the producing organ of the nail. This is thick and highly 

 vascular, and its colour is seen through the transparent tissue. 

 Near the root it is white, and occasions the appearance termed 

 lunula. The nail has a firm adherence to the matrix, and is 

 moulded upon it, like the epidermis in other situations. The true 

 epidermis (as distinguished from the nail) is continuous with the 

 nail at the whole circumference of its body ; the root dips into 

 the fold of cutis, within the epidermis, and the free edge pro- 

 jects beyond it. In the advanced foetus we find the edge of 

 the nail to be directly continuous with the epidermis of the end 



* Dr. Simon, of Berlin, has ably investigated this part of the subject. 

 Miiller's Archiv. 1840. t See Dr. Prichard, Natural History of Man. 



