226 GENERAL ANATOMY. 



The colour of the skin is also subject to accidental altera- 

 tions: thus we see individuals among the whites become brown, 

 or perfectly black, in places of more or less extent. Whites 

 and blacks also become albinoes in points of the skin more or 

 less extensive. 



May not the melanosis which usually coincides with the dis- 

 colouration of the skin, and which is so often observed in white 

 hairs, depend upon an aberration of the pigment of the skin? 



Horny productions, which project more or less from the 

 surface of the skin, are sometimes found in the corpus muco- 

 sum; these productions being analogous to the nails, will be 

 described after these appendages of the skin. 



ARTICLE II. 

 OF THE APPENDAGES OF THE 



327. The nails and hairs are the only appendages of the 

 human skin; in animals, on the contrary, they exist in great 

 numoers and variety. It is an error to consider these parts as 

 appendages of the epidermis alone, for they are connected with 

 the whole skin. 



1. OF THE NAILS.* 



328. The nails, ungues, are horny scales which cover the 

 skin of the last phalanx of the fingers and toes, on the side of 

 the extensors. 



Three parts are noticed in the nail, viz: the root, the body, 

 and the free extremity. 



The root or adhering extremity, is the fifth or sixth part of 

 the length of the nail; it is the thinnest part of it; it is received 

 nto a groove in the skin, and is of a white colour. The body, 



* Frankeneau, de Unguibus. Jenoe, 1796. Ludvvig, de ortu et structure! 

 unguium. Lipsiae, 1748. B. S. Albinus, in Arinot. acad. lib. ii. cap. xiv. 

 de Ungue humano, ejusque reticulo &?c., et cap. xv. de Natura unguis. Bose, 

 de Unguifas humanit. Lips. 1773. Haase, de Nutritione unguium. Lips. 

 1774. 



