Chai'. VII. T lie Formation of Races. 193 



present homes, does not coiucidc with corresponding difl'eronces 

 of climate. Some little weight may be given to such cases as 

 that of the Dutch families, who, as we hear on excellent autho- 

 rity,*' have not undergone the least change of colour after 

 residing for three centuries in South Africa. An argument on 

 the same side may likewise be drawn from the uniform appear- 

 ance in various parts of the world of gipsies and Jews, though 

 the uniformity of the latter has been somewhat exaggerated."* 

 A very damp or a very dry atmosphere has been supposed to be 

 more influential in modifying the colour of the skin than mere 

 heat ; but as B'Orbigny in South America, and Livingstone in 

 Africa, arrived at diametrically opposite conclusions with respect 

 to dampness and dryness, any conclusion on this head must be 

 considered as very doubtful.*^ 



Various facts, which I have given elsewhere, prove that the 

 colour of the skin and hair is sometimes correlated in a surpris- 

 ing manner with a complete immunity from the action of certain 

 vegetable poisons, and from the attacks of certain parasites. 

 Hence it occurred to me, that negroes and other dark races 

 might have acquired their dai'k tints by the darker individuals 

 escaping from the deadly influence of the miasma of their 

 native countries, during a long series of generations. 



I afterwards found that this same idea had long ago occurred 

 to Dr. Wells.''' It has long been known that negroes, and even 

 mulattoes, are almost completely exempt from the yellow fever, 

 ' so destructive in tropical America." They likewise escape to a 

 large extent the fatal intermittent fevers, that prevail along at 

 least 2600 miles of the shores of Africa, and which annually 

 cause one-fifth of the white settlers to die, and another fifth to 

 return home invalided.^' This immunity in the negro seems to 

 be partly inherent, depending on some unknown peculiarity of 

 constitution, and partly the result of acclimatisation. Pouchet" 



" Sir Andrew Smith, as quoted the Historical Slcetch (p. xvi.) to my 



by Knox, * Eaces of Man ' 1850, p. * Origin of Species.' Various cases 



473. of colour correlated with constitu- 



^^ See De Quatrefages on this tional peculiarities are given in my 



head, * Revue des Cours Scienti- ' Variation of Animals under Do- 



fiques,' Oct. 17, 1868, p. 731. mestication,' vol. ii. pp. 227, 335. 



** Livingstone's * Travels and Re- '■' See, for instance, Nott and 



searches in S. Africa,' 1857, pp. Gliddon, ' Types of Mankind,' p. 68. 



338, 329. D'Orbigny, as quoted by '^ Major Tulloch, in a paper read 



Godron, ' De TEspfece,' vol. ii. p. before the Statistical Society, April 



266. 20th, 1840, and given in the ' Athe- 



'° See a paper read befoi'e the na=um,' 1840, p. 353. 



Koyal Soc. in 1813, and published =* 'The Plurality of the H«m;iii 



2 his Essays in 1818. I have given Race ' (transl.at.), 1S64, p. (!0. 

 in account of Dr. Wells' views in 



14 



