EVOLUTION AGAINST DISEASE 141 



(Negroes from the East Coast of Africa) who had been im- 

 ported at various times by the Dutch Government into 

 Ceylon, and had been drafted into regiments, scarcely a trace 

 of their descendants remains ; they would certainly not be 

 recognized at all among the present population of the island. 

 In the years 1803 and 1810 the British Government im- 

 ported three or four thousand Negroes from Mozambique into 

 Ceylon to form into regiments, and of these in December 1820 

 there were left just 440, including the male descendants." l 

 All the rest had perished mainly from tuberculosis, and in a 

 country where the disease is not nearly so prevalent as in 

 England. 



227. We habitually speak of the fatal " climate " of the 

 West Coast of Africa or of the Terai ; but we are usually 

 unaware that our own " climate " at the present day is nearly, 

 if not quite, as fatal to the native inhabitants of much the 

 greater part of the world of all the New World and of Africa, 

 a considerable portion of Asia, and part of Europe and that, 

 therefore, our race, which is able to persist under such adverse 

 conditions, has undergone evolution in relation to tuberculosis 

 fully equal to the evolution against malaria undergone by the 

 West Africans. 



The micro-organisms of tuberculosis, since they are essen- 

 tially earth-borne and entirely parasitic, and since strong sun- 

 light is highly inimical to them, are unable to persist except 

 under given conditions, which are best satisfied in the crowded, 

 badly-ventilated and ill-lighted houses of civilized people 

 particularly those that dwell in the cities of cold and temperate 

 climates. That the environment is yearly growing more favour- 

 able to the bacilli in the world at large, especially in newly 

 colonized areas, in consequence of the increase of population, 

 cannot be doubted, and this in spite of the greater attention 

 which is now-a-days paid, in some places, to light and ventil- 

 ation. It is calculated that at the present time at least one- 

 seventh or one-eighth of the total number of deaths is due to 

 its agency. But it is death-dealing to a vastly greater extent 

 under circumstances which are even more favourable to it 

 than such as normally obtain. For instance, in prisons, 

 barracks, convents and the like, the death-rate is apt to be 

 enormous, as may be judged from the following : 



228. " Phthisis in prisons. Consumption prevails in prisons 

 to a truly disastrous extent. I take the following statistical 

 data from an excellent article on the subject by Baer. In the 

 United States prisons, from 1829 to 1845, the mortality from 



1 Hirsch, vol. iii., p. 226. 



