On (he Unity of the Human Species. 25 



The observations by means of which we have supported 

 the beautiful opinion of the primitive unity of the human 

 species, do not, however, demonstrate it in a direct manner. 

 M. Flourens comes to our aid and supplies this deficiency : 

 by a comparative study of the different structures of the 

 human organism, he has arrived at the same result which 

 had been reached by following another path. 



He has commenced this study by an examination of the 

 skin, considering it among the races where this organ is 

 coloured, and among such as present no sensible colour. In 

 the first, there is found a pigmental membrane or /i2^;rte«^Mm, 

 which is not seen in the second, except on certain parts of 

 the body. This membrane, discovered by Ruysch in Negroes, 

 had been considered, from the observations of that author, as 

 characterising certain races, just as its absence distinguished 

 others. But it is far from possessing the importance which 

 was at first assigned to it. 



The skin of a White man, by exposure to the sun, acquires 

 a very thin layer of pigmentum between the second epider- 

 mis and the true skin, that is to say, in the same place as 

 in the Negro. It may be said that the accidental color- 

 ation, produced by the sun, alters the cellular tissue and 

 produces the pigmental substance peculiar to the coloured 

 races. But it must be further observed, that the white man is 

 not exempt from the common law. Even in his natural state 

 his skin has its pigmentum, very inconsiderable, indeed, but 

 still sufficiently perceptible. That part of the breast, which 

 is named the nipple, is, as is well known, of a dark colour, 

 in the male, and more particularly in the female of the white 

 race. We there find a pigmental apparatus, so that this part 

 of the skin exhibits, in the white race, the structure existing 

 in that of the coloured races. 



This membrane, connected with the coloration of the skin, 

 is not therefore essential to the nature of the races ; it can- 

 not be considered as charactei-ising them, since the skin of 

 the fcctus in the negro shews not the least trace of it. So 

 far is it from being essential, that we do not perceive the 

 slightest indication of it in those individuals of the coloured 

 races who are af!ected with partial albinism. In such cases 



