INTRODUCTION. 25 



and thickness of the neck are very characteristic of breeds of horses ; 

 Meckel remarks that the length, height, and proportional breadth of 

 the hinder parts, the length and thickness of the tail, the shape of 

 the pelvis, and comparative length of the limbs, are characteristic 

 of different races. The physiological and psychological differences 

 we have seen are equally remarkable. 



Races of men are subject, more than the races of almost any ani- 

 mals, to the varied agencies of climate ; civilization produces in 

 them greater changes than does domestication in animals ; and we 

 ought, therefore, to expect as great diversities among men as among 

 brutes, and indeed far greater, from the powerful influence of mind 

 in the former. 



To proceed with the variations of the human species, we are at 

 first struck with the differences of color. The difference of color 

 tas generally been thought less important in the discrimination of 

 the races than varieties in the form of the skull ; but M. Flourens 

 considers it more characteristic of distinct races than any other 

 peculiarity. lie displayed before the French Academy of Sciences 

 four distinct layers between the outer cuticle and the cutis, viz., a 

 cellular and reticular tissue lying immediately on the cutis; then a 

 continuous membrane resembling mucous membrane in general ; then 

 a black pigment, hardly coherent enough to be termed a membrane ; 

 and, lastly, the interior portion of the epidermis, which he divides 

 into two lamina;. The second of these he considers a distinct 

 organized body, existing only in men of dark color, or, at least, t»" 

 failed to delect it in tin' white races by the ordinary method of mac- 

 eration. He was unable to find any membrane in the white i 

 interposed between the cutis and the inner coat of the epidermis ; 

 this last being, according to him, the seat of the discoloration of 

 the white skin from exposure to the sun, as well as the seat of the 

 brown color of the areola mammarum. This diversity he regards 

 as a specific distinction, "or as marking out the >,'e;!;ro and Euro- 

 pean as separate species of beings." 



The supposition of M. Flourens will hardly account for many 

 discolorations of the skin which are frequent in Europeans. Dur- 

 ing pregnancy, the mamma; of many females are extensively sur- 

 rounded by a dark tinge, which afterwards mostly disappears ; in 

 some individuals the dark color pervades a great part of the body ; 

 so that, independently of the solar heat, certain constitutional condi- 

 tions may impart to the white skin a dark hue similar to that nat- 

 ural to the African race. On the other hand, instances are recorded 

 (in Philos. Trans., vol. 57) of the disappearance of the coloring 

 matter in Negroes, who have become as white as Europeans. 

 3 



