for the people of Southern Asia, whilst, similarly taken, it may be good for Europeans. However this may be, Burmah is not India, and it is not reasonable to apply to India conclusions based upon observations made in a totally different country. It appears to me as regards India, properly so called, there is no evidence whatever to show that in any part of the country the consumption of opium is anywhere a common and crying evil. Of course I admit that the use of opium may be abused, but I entirely disbelieve that this occurs to any general or dangerous extent."—Ibid. pp. 66–7.
À posteriori considerations therefore abundantly confirm the conclusion we came to on à priori grounds; namely, that wherever the death-dealing narcotic opium is in common use as an intoxicant, there it must be a cause of evolution also.
Evolution against any one zymotic disease is not protective to any extent against other zymotic diseases. It would be interesting to know whether the same law obtains as regards evolution against the various deadly narcotics: for instance, it would be interesting to know whether evolution against alcohol is, or is not, protective against opium. Are the weak against alcohol, they who crave greatly for it, the weak against opium also? Or is the one craving a thing distinct and separate from the other? It is very rare for both cravings to be manifested in the same person; indeed I do not remember to have heard of a case where this occurred to any extent; but, on the other hand, the cravings for alcohol and tobacco very often co-exist. It seems probable, therefore, that the cravings for those states of mind that alcohol and opium (and other narcotics) severally induce are distinct and separate, just as the weaknesses against separate zymotic diseases are distinct and separate, and therefore it seems probable
