294 THE PRESENT EVOLUTION OF MAN — PHYSICAL 



to their nationality, or to what extent it may be so due, 

 we are unable to decide. It is certain, however, tliat the 

 amount of the disease increases considerably among 

 negroes away from their native countries, an increase 

 that deiDcnds in part upon the manner of living. The 

 extent to which a change of climate may operate in 

 that direction Avill appear from the phthisis mortality 

 among negro troops in the British service at certain 

 military stations. 



COMPAEATIVE TABLE OF PHTHISIS AMONG 

 BRITISH AND NEGRO TROOPS. 



" Here we have confirmation of the well-known fact, 

 that the migration of the negro to a colder climate is 

 accompanied by a rise in the phthisical average ; but it 

 is obvious that we should also make allowance for 

 changed habits of living as weighing not less in the 

 scale. Pruner calls attention to a fact that has a 

 bearing on the question, namely, that at Khartoum, in 

 latitude 17° N., with a temperature not lower than that 

 of the mountains around, consumption ensues among 

 negro captives, as well as among the Arabs of the 

 desert, whenever they give up their nomadic life to live 

 under a roof, even if it be in a warmer region. 



" Here also an important part among the disease- 

 factors is jjlayed without doubt by bad food, insufficient 

 clothing, and confinement in crowded, filthy, and badly- 

 ventilated huts ; and there is nothing to surprise us in 

 the experience that consumption has increased to an 

 alarming extent amono- the neojroes of Arkansas of late, 

 or since their emancipation, the result being due, as the 



