Of the innumerable chemical substances other than foodstuffs which the world contains, none have a moreintimate connection with human life than those whose history and effects are described in this work.

If human consciousness is the most wonderful thing on earth, the attempt to fathom the depths of thepsychophysiological action of narcotic and stimulating drugs makes this wonder seem greater still, for withtheir help man is enabled to transfer emotions of everyday life, as well as his will and intellect, to unknownregions; he is enabled to attain degrees of emotional intensity and duration which are otherwise unknownto the brain. Such effects are brought about by chemical substances. The most powerful of these areproducts of the vegetable kingdom, into whose silent growth and creative abundance man has not yet fullypenetrated. By the exercise of their powers on the brain, they release marvelous stores of latent energy.They relieve the mentally tortured, assuage the racking pains of the sick, inspire with hope those doomed todeath, endow the overworked with new vitality and vigour such as no strength of will could attain, andreplace for an hour the exhaustion and languor of the overworked by mental comfort and content.

-- L. Lewin (1924)