Chap. VII. 
THE KACES OF MAN. 
243 
occurred to Dr. Wells. 43 That negroes, and even mulat- 
toes, are almost completely exempt from the yellow- 
fever, which is so destructive in tropical America, has 
long been known. 44 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. 45 This immu- 
nity in the negro seems to be partly inherent, de- 
pending on some unknown peculiarity of constitution, 
and partly the result of acclimatisation. Pouchet 46 
states that the negro regiments, borrowed from the 
Viceroy of Egypt for the Mexican war, which had been 
recruited near the Soudan, escaped the yellow-fever 
almost equally well with the negroes originally brought 
from various parts of Africa, and accustomed to the 
climate of the West Indies. That acclimatisation plays 
a part is shewn by the many cases in which negroes, 
after having resided for some time in a colder climate, 
have become to a certain extent liable to tropical 
fevers. 47 The nature of the climate under which the 
white races have long resided, likewise has some in- 
fluence on them ; for during the fearful epidemic of 
yellow-fever in Demerara during 1837, Dr. Blair found 
that the death-rate of the immigrants was proportional 
43 See a paper read before the Eoyal Soc. in 1813, and published in 
his Essays in 1818. I have given an account of Dr. Wells’ views in the 
Historical Sketch (p. xvi) to my ‘ Origin of Species.’ Yarious cases of 
colour correlated with constitutional peculiarities are given in my 
‘ Variation of Animals under Domestication/ vol. ii. p. 227, 335. 
44 See, for instance, Nott and Gliddon, * Types of Mankind,’ p. 68. 
45 Major Tulloch, in a paper read before the Statistical Society, 
April 20th, 1840, and given in the ‘ Athenaeum, ’ 1840, p. 353. 
46 ‘ The Plurality of the Human Race ’ (translat.), 1864, p. 60. 
47 Quatrefages, ‘Unite de l’Espece Humaine/ 1861, p. 205. Waitz, 
‘ Introduct. to Anthropology/ translat. vol. i. 1863, p. 124, Living- 
stone gives analogous cases in his ‘ Travels/ 
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