The crudest of these methods of influencing the body, but also the most effective, is the chemical one: that of intoxication. I do not think anyone entirely understands their operation, but it is a fact that there are certain substances foreign to the body which, when present in the blood or tissues, directly cause us pleasurable sensations, but also so change the conditions of our perceptivity that we become insensible of disagreeable sensations. The two effects not only take place simultaneously, they seem to be closely bound up with each other. But there must be substances in the chemical composition of our bodies which can do the same, for we know of at least one morbid state, that of mania, in which a condition similar to this intoxication arises without any drug being absorbed. Besides this, our normal mental life shows variations, according to which pleasure is experienced with more or less ease, and along with this goes a diminished or increased sensitivity to pain. It is greatly to be regretted that this toxic aspect of mental processes has so far eluded scientific research. The services rendered by intoxicating substances in the struggle for happiness and in warding off misery rank so highly as a benefit that both individuals and races have given them an established position within their libido-economy. It is not merely the immediate gain in pleasure which one owes to them, but also a measure of that independence of the outer world which is so sorely craved. Men know that with the help they can get from ‘drowning their cares’ they can at any time slip away from the oppression of reality and find a refuge in a world of their own where painful feelings do not enter. We are aware that it is just this property which constitutes the danger and injuriousness of intoxicating substances. In certain circumstances they are to blame when valuable energies which could have been used to improve the lot of humanity are uselessly wasted.