354 THE PRESENT EVOLUTION OF MAN — MENTAL 



In the effects produced by it, both on the individual 

 and on the race, opium appears to lie midway between 

 tobacco and alcohol. As in the case of nicotine, experi- 

 ence of it by the individual induces a great protective 

 reaction — enables the individual to tolerate immensely 

 larger doses of the poison — but this protective reaction, 

 this power of acquiring immunity, is not so complete 

 in the case of opium as it is in the case of nicotine, 

 since increased indulgence in the former may reproduce 

 even in the most experienced individual those symptoms 

 of immediate poisoning which indulgence in it first 

 produced. At the least this is true ; that while habit- 

 ual indulgence in tobacco tends to cause, even in 

 individuals of a race that has had no experience of it, a 

 protective reaction, in consequence of which the indivi- 

 dual no longer craves for indulgence in it to such an 

 extent as to reproduce the symptoms of immediate 

 poisoning which he felt when first he indulged in the 

 poison, habitual indulgence in opium by individuals of 

 a race that has had no experience of it, very rarely 

 results in a protective reaction of such a nature that the 

 individual no longer craves for indulgence in it to such 

 an extent as to reproduce those symptoms of immediate 

 poisoning which he felt when first he made the ac- 

 quaintance of the narcotic. On the contrary, such an 

 individual, notwithstanding the protective reaction he 

 undergoes, whereby he is enabled to withstand increased 

 doses, yet generally craves for indulgence to such an 

 extent as to reproduce the symptoms of immediate 

 poisoning ; and therefore — as in the case of alcohol — 

 indulgence in opium to the full extent of his desire 

 tends to bring about his elimination ; whence it follows 

 that opium, like alcohol and unlike tobacco, is a cause 

 of evolution — an evolution which is mainly from a 

 greater craving towards a lesser craving, not mainly 

 from a lesser power of toleration towards a greater power 



