We may now touch upon a different aspect of the drink problem. How are we to account for the deep-rooted and widespread love of alcohol shown by mankind? One fact stands out prominently in this connexion, namely, that man all the world over displays an instinctive liking for stimulating substances generally. This is shown by such practices as betel chewing in the East and pitcheree chewing among the Australians.
Can we bring this love of things stimulating into line with any physiological principle? We would suggest that the blood normally contains materials having an action on the nervous system not unlike that of alcohol and kindred substances. We now know that this remarkable fluid - the most subtly complex in nature - contains, besides nutrient materials and useless waste-products, substances (hormones) whose special purpose it is to stimulate function. Our knowledge of their action on the nervous system is at present limited, but it may well be that they play a much larger part in this direction than has hitherto been suspected. It is probable that some hormones exercise a sedative, others a tonic, and others, again, a stimulating, or even slightly intoxicating, effect upon the brain, much in the same way as do morphia, strychnine, and alcohol, and that the sense of exuberant well-being sometimes experienced is in large measure due to the combined action of such substances, just as the opposite condition of lassitude and depression may be due to the accumulation in the blood of others having a contrary effect. We may, in short, think of the brain as an instrument played upon by a number of chemical agencies which may be roughly grouped into stimulants and depressants, i.e. those which cause a sense of well-being and those which cause malaise, and we may conceive of this mind-instrument as yielding harmonies joyous or sad according as the one or the other group of agencies strikes the tune.
Now, given that the blood normally contains mildly sedative, tonic, and stimulating substances, and that the sense of exuberant well-being and joyous emotion is largely due to them, is it any wonder that man, having discovered an essence capable of producing similar effects, should, all ignorant of the danger he runs, fly to it with the blind impetuosity of the moth rushing into the destroying flame?
We must not be misunderstood here. We are very far from arguing that, because the tissue fluids normally contain substances which engender feelings of health and happiness, man therefore stands in need of artificial stimulants. The normal nerve stimulants are of such nature and present in such proportions, as to promote rather than to injure health, whereas alcoholic drinks, even when taken in moderation, are apt to be harmful, and are but too often imbibed in quantities which are unmistakably poisonous. It is even possible that an excess of the normal blood stimulants would be injurious. We have merely sought to offer a physiological explanation of the all but universal liking of men for artificial stimuli of one sort or another.
Here we are tempted to raise the question whether the impulsive craving for alcohol sometimes observed in the congenital neurotic may not possibly be due to the deficiency in the blood of its normal proportion of stimulants. That dypsomania showing itself in paroxysmal craving for alcohol owns such a pathology seems not unlikely. Be this as it may, we feel assured that the nervous diathesis is essentially dependent upon the composition of the blood - that an individual is nervously disposed because his blood makes him so.