Page:George Archdall Reid 1896 The present evolution of man.djvu/364

352 fore, the race is protected only by the inborn power of making immediate resistance.

In all this there is a close analogy between narcotics and diseases. Against some narcotics—e.g. tobacco—the individual, even of a race that is strange to them, easily acquires immunity; that is, the cells concerned (nervecells) not only acquire the power of tolerating the poison (toxin), but the craving for it is satisfied in the individual by a limited and generally harmless degree of indulgence; and therefore since such narcotics are the cause of little or no elimination, they are the cause of little or no evolution; and races that have longest experienced them, crave for indulgence in them as greatly as races that have had little or no experience of them. On the other hand, there are other narcotics—e.g. alcohol—against which powers of making resistance cannot be acquired to nearly so great an extent. For instance, no man can tolerate alcohol to nearly such an increased extent as he can nicotine, as a result of individual experience of it; that is, no amount of indulgence can reproduce in the experienced smoker those immediately poisonous effects of nicotine which his first indulgence in tobacco produced, whereas a slight increase of indulgence will reproduce in the drinker those immediately poisonous effects of alcohol which he experienced when first he indulged in the poison. The power of making resistance to alcohol, unlike the power of making resistance to nicotine, is therefore mostly of the inborn kind. The individual craving for it in races not rendered resistant by evolution in the ancestry is not satisfied by a degree of indulgence so limited that it is generally harmless, but only by a degree of indulgence which is exceedingly harmful; and therefore, since such narcotics are the cause of much elimination, they are the cause of much evolution; whence it follows, that races that have longest experienced them crave