Even in countries where the pathogenic organisms are most abundant they are not everywhere present, but are more or less limited to crowded and ill-ventilated domiciles to which infected persons have access. Individual powers of resistance, even among peoples to which the disease is quite strange, vary largely. Parties of strangers from beyond the infected areas are therefore never stricken down en masse, but one by one, at different intervals; and the symptoms noticeable in the sufferers are such as are referable by unskilled observers to other diseases—colds, coughs, &c. Last, but not least—among the races which are least resistant to malaria is our own; on the other hand, it is among the most resistant to tuberculosis; and therefore our attention is not drawn, in the same marked manner, to racial differences in relation to the latter disease as it is to differences in relation to the former. We have all heard, for instance, of the sufferings from malaria of our compatriots in India and on the West Coast of Africa, and that in the year 1809 a British army was, as a fighting force, destroyed by the same cause in the Island of Walcheren, but few of us know,
"That of 9000 Kaffirs (negroes from the East Coast of Africa) who had been imported 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 imported some 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."—Hirsch, vol. iii. p. 226.
All the rest had perished, mainly from tuberculosis,
