CHAPTER IV
Opium and other narcotics.—After having devoted so much space to alcohol, it is not necessary to dwell at length on the other narcotics, the use of which has resulted in mental evolution; that is, which have been sufficiently poisonous and prevalent to have caused a considerable elimination of the unfit in relation to them, in this resembling prevalent and deadly diseases—e.g. malaria and tuberculosis,—and differing from diseases which though deadly are not prevalent—e.g. rabies,—and diseases which though prevalent are not deadly—e.g. chicken-pox; which last diseases, in the absence of any appreciable evolution caused by them, are resembled by such prevalent but comparatively innocuous narcotics as tobacco. The evolution against the other deadly and prevalent narcotics must have proceeded on much the same lines as that against alcohol, and against deadly and prevalent forms of zymotic disease. The gradual improvements in the manufacture of such narcotics—i.e. the gradual increase in the poisonous nature of the preparations of them manufactured by races that had discovered their use—must have been accompanied, as in the case of alcohol, by a protective evolution whereby, through survival of the fittest, the craving grew less. Doubtless, however, since the manufacture of strong—i.e. poisonous—preparations of some of them is much easier, and less complicated than the
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