There is a fact of singular interest in relation to the intoxicants I have now described or named, and which before I proceed further should be carefully noticed. The fact is this: That when the agents produce a definite effect upon a living body, whether it be a human body or the body of an animal that possesses desires and likings, there is caused in that body, after a number of times of practice, a craving or desire for the agent that produced the effect. In man this is so marked that the most repugnant and painful of lessons connected with the first subjection to the agent is soon forgotten in the acquired after-sense of craving or desire. It really matters little which of the intoxicants it is that is learned to be craved for; the craving for it will continue when it has struck an abiding impression. We know this fact well from the wide experience that has been gained of it in the cases of alcohol, tobacco, opium, chloral, hasheesh, absinthe, and arsenic. More incongruous things could scarcely be; incongruous to the senses, to the sensibilities, to the methods of taking, to the result of them; yet the craving for any one of them as it is may be established. The devotee to one will laugh at the devotee to another; each one will consider the other almost insane, and yet each will follow his own course.
Still more curious is it that the substances craved for, which lie quite outside the natural wants of healthy life, may be extended to any number. There is in truth hardly a substance to which the craving may not cling. The distinguished Dr. Huxham had under his observation a man who, after a little practice in the habit of taking it, had a craving for the salt now called bicarbonate of ammonia. The man chewed this salt and swallowed it in the same way as he might have swallowed peppermint lozenges. The effect of the salt was to produce extreme fluidity of the blood of the man, so that he became scorbutic, and to cause loosening of his teeth. It also reduced his strength, and even placed his life in jeopardy; and yet his craving for the ammonia remained unappeased until his danger was so great that the noxious thing had to be withheld altogether. The great Sir Humphry Davy gives another, and it may be still more remarkable, experience in relation to himself. When he was making his wonderful researches with nitrous-oxide gas, he commenced, at first for the mere sake of experiment, to inhale the gas in free quantities. By this process of inhalation he obtained the most delicious of visions. Space seemed to him illimitable, and time extended infinitely, so that coming out of one of these trances he exclaimed: "Nothing exists but thoughts; the universe is composed of impressions, ideas, pleasures, and pains!" In course of time Davy, by the frequent repetition of the process of inhalation, became so infatuated that he could not look at a gasholder, could not look at a person breathing—I am using his own description—without experiencing the urgent sense of desire to once more imbibe his favorite gaseous nectar, and revel in his induced and artificial dreams. How
