THE FORMATION OF RACES. 189 



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

 be partly inherent, depending on some unl^nown peculiarity of 

 constitution, and partly the result of acclimatization. Pouchet" 

 states that the negro regiments recruited near the Soudan, and 

 borrowed from the Viceroy of Egypt for the Mexican war, 

 escaped the yellow-fever almost equally with the negroes origin- 

 ally brought from various parts of Africa and accustomed to the 

 climate of the West Indies. That acclimatization plays a part, 

 is shown by the many cases in which negroes have become some- 

 what liable to tropical fevers, after having resided for some time 

 in a colder climate.™ The nature of the climate under which the 

 white races have long resided, likewise has some influence on 

 them; for during the fearful epidemic of yellow -fever in Dem- 

 erara during 1837, Dr. Blair found that the death-rate of the 

 immigrants was proportional to the latitude of the country 

 whence they had come. With the negro the immunity, as far as 

 it is the result of acclimatization, implies exposure during a 

 prodigious length of time; for the aborigines of tropical America 

 who have resided' there from time immemorial, are not exempt 

 from yellow fever; and the Rev. H. B. Tristram states, that there 

 are districts in Northern Africa which the native inhabitants are 

 compelled annually to leave, though the negroes can remain with 

 safety. 



That the immunity of the negro is in any degree correlated 

 with the color of his skin is a mere conjecture: it may be cor- 

 related with some difference in his blood, nervous system, or 

 other tissues. Nevertheless, from the facts above alluded to, and 

 from some connection apparently existing between complexion 

 and a tendency to consumption, the conjecture seemed to me not 

 improbable. Consequently I endeavored, with but little success," 



=8 Major Tulloch, In a paper read before the Statistical Society, 

 April 20th, 1840, and given in the 'Athenaeum,' 1840, p. 353. 



« 'The Plurality of the Human Race,' (translat.), 1864, p. 60. 



«> Quatrefages, 'Unite de I'Espece Humaine,' 1861, p. 205. Waitz, 

 'Introduct. to Anthropology,' translat. vol. i. 1863, p. 124. Livingstone 

 gives analogous cases in his 'Travels.' 



''I In Ihe spring of 18G2 I obtained permission from the Director-Gen- 

 eral of the Medical department of the Army, to transmit to the sur- 

 geons of the various regiments on foreign service a blank table, with 

 the following appended remarks, but I have received no returns. "As 

 "several well-marked cases have been recorded with our domestic 

 "animals of a relation between the color of the dermal appendages 

 "and the constitution; and it being notorious that there is some lim- 

 "ited degree of relation between the color of the races of man and 

 "the climate inhabited by them; the following investigation seems 

 "worth consideration. Namely, whether there is any relation in Eu- 

 "ropeans between the color of their hair, and their liability to the dls- 

 "eases of tropical countries. If the surgeons of the several regi- 



