238 THE DESCENT OF MAN. [Part I. 



inhabitants of tropical America, are wholly different from 

 the Negroes who inhabit the opposite shores of the At- 

 lantic, are exposed to a nearly similar climate, and follow 

 nearly the same habits of life. 



Nor can the differences between the races of man be 

 accounted for, except to a quite insignificant degree, by 

 the inherited effects of the increased or decreased use of 

 parts. Men who habitually live in canoes may have their 

 legs somewhat stunted ; those who inhabit lofty regions 

 have their chests enlarged ; and those who constantly use 

 certain sense-organs have the cavities in which thev are 

 lodged somewhat increased in size, and their features con- 

 sequently a little modified. With civilized nations, the 

 reduced size of the jaws from lessened use, the habitual 

 play of different muscles serving to express different emo- 

 tions, and the increased size of the brain from greater in- 

 tellectual activity, have together produced a considerable 

 effect on their general appearance, in comparison with 

 savages. 52 It is also possible that increased bodily stature, 

 with no corresponding increase in the size of the brain, 

 may have given to some races (judging from the pre- 

 viously adduced cases of the rabbits) an elongated skull 

 of the dolichocephalic type. 



Lastly, the little-understood principle of correlation 

 will almost certainly have come into action, as in the case 

 of great muscular development and strongly-projecting 

 supra-orbital ridges. It is not improbable that the texture 

 of the hair, which differs much in the different races, may 

 stand in some kind of correlation with the structure of 

 the skin ; for the color of the hair and skin are certainly 

 correlated, as is its color and texture with the Mandans. 63 



52 See Prof. Schaaffhausen, translat. in 'Anthropological Review,' 

 Oct. 1868, p. 429. 



53 Mr. Catlin states (' North American Indians,' 3d edit. 1842, vol. i. p. 

 49) that, in the whole tribe of the Mandans, about one in ten or twelve 



