Page:George Archdall Reid 1896 The present evolution of man.djvu/316

their areas of distribution, or so fatal as the three already discussed, at least as regards malaria and tuberculosis, evolution against few others is so marked as against them. Moreover, most of the other very prevalent and fatal diseases against which considerable evolution has occurred are those affecting the alimentary tract, i.e. are those in which, generally speaking, infection depends on the character of the food and water supply, and therefore, as regards them, since strangers who enter the infected districts are usually Europeans, more careful as to their food and water supply than the Natives of Africa and Asia, where these diseases chiefly prevail, they usually suffer from them less in proportion to their susceptibility than the natives. For instance, Europeans actually suffer less from cholera in India than do the natives, though their great susceptibility is proved by the history of various pandemics, during which the disease overpassed its normal boundaries, and ravaged Europe. It is therefore difficult to measure with any degree of accuracy the extent of the evolution undergone by races that have had extended and disastrous experience of these diseases, for we cannot with accuracy contrast them with races which have had little or no experience of them, and have therefore undergone no evolution in relation to them. Nevertheless, in all publications in which the subject is alluded to—official reports, medical works, travels, &c.—we continually meet statements, collectively so numerous that volumes might be filled with them, that tend to show that the evolution has been considerable. Thus we read that, owing to malaria and dysentery, Muscat is uninhabitable by Europeans during the summer months;^[1] That in the districts infested by yellow fever strangers are vastly more liable to attack than natives;^[2] that in Ceylon the mortality from dysentery among the troops reached the

1. Hirsch, vol. iii. p. 293.
2. Ibid. vol. i. p. 340.