Alcohol modifies the results of respiration in a constant manner and in all doses. This modification consists in a decrease in the amount of oxygen absorbed and carbon dioxide exhaled. This effect is usually more marked when alcohol is taken fasting than during digestion.
The influence of alcohol upon the renal secretion is that of a diuretic, but the fact must not be overlooked that this tendency is much increased by the large amount of water which alcoholic drinks necessarily contain. But that alcohol acts as a diuretic, even in small doses and altogether independently of the water with which it is taken, does not admit of doubt. The changes in the urine are qualitative as well as quantitative. The amount of urea, uric acid, and other solids is always notably diminished. The diminution of the amount of phosphoric acid is even greater than that of the nitrogenized substances, especially during the period of excitation.
The diuretic effect of alcohol is dependent upon its direct action on the parenchyma of the kidneys, the qualitative changes in the urine upon its influence on nutrition.
Upon the temperature of the body alcohol has a marked effect. The sensation of warmth experienced after moderate doses is chiefly subjective, and is accompanied by a very slight actual rise in temperature, amounting to some fraction of a degree Fahrenheit, and of but short duration. This rise is followed by a rapid fall, amounting to a degree or more below the norm. This effect is manifested within the course of an hour after the administration, and is of comparatively brief duration, being largely influenced by the condition of the individual at the time as regards mental or physical exercise, digestion, and the like. It is in part due to the increased loss of heat from the surface of the body, favored by more active cutaneous circulation, but chiefly to the action of alcohol in retarding oxidation and the activity of nutritive changes. Toxic doses are followed by marked fall of temperature. The influence of alcohol upon the temperature is more pronounced in febrile conditions than in health.
The influence of physiological doses of alcohol upon the nervous system is, among all its effects, the most marked and the most difficult to describe with exactitude. It is usual to regard this agent as a stimulant and to separate the period of its direct effects into two stages—that of excitement and that of depression. John Hunter defined stimuli as agents which increase some natural action or tendency, in contradistinction to irritants, which produce actions altogether abnormal. Anstie12 sought to restrict the use of the term stimulant to agents which by their direct action tend to rectify some deficient or too redundant natural action or tendency. Without entering upon the discussion of the doctrine of stimulation, I may say that the views of Anstie have served a useful purpose in making clear some vexed questions. In accordance with these views, the physiological action of alcohol is followed neither by excitement nor by depression, and when its administration is followed by these conditions, its action is not truly physiological, but narcotic or toxic.
12 Stimulants and Narcotics, Lond., 1864.
The effects of this agent upon the nervous system vary within very wide limits according to innumerable conditions which relate to the temperament, health, habits, occupation of the individual, season, climate, social circumstances, and the quantity, kind of alcoholic drink, and its mode of administration. Its first action in moderate doses and under circumstances free from complications is to increase the functional activity of the brain: the ideas flow more easily, the senses are more acute, speech is fluent, and movement active. These effects accompany the increase in the heart's action, the slight rise in temperature already described, and increased activity of the organism in general. They appear to be in part due to the direct action of the substance upon the cerebrum, and in part to increased activity of the circulation. The effect upon the nervous system has been compared by Nothnagel to the effect, in a higher sphere, of strong moral impulses. Without otherwise modifying existing traits of character, such impulses call them into action, and lead to the accomplishment of deeds quite impossible under ordinary circumstances. To a man worn out by some prolonged task which from sheer fatigue he despairs of finishing, let there be announced some joyful news; he at once feels refreshed, applies himself with renewed energy to his work, and perhaps finishes it with ease. In kind at least this is the effect also of alcohol.
But the limits of the physiological effects are easily transcended, and the manifestations then become those of its toxic influence, between the slightest grades of which and drunkenness the difference is one rather of degree than of kind. These effects must therefore be described under the heading Acute Alcoholism.
Passing to the influence of alcohol upon nutrition, we recognize two modes of action. Of these the first is direct and in part local, and results from the stimulation of the glandular apparatus of the mucous membrane of the mouth and stomach, from increased activity of the circulation, and from direct stimulation of the pneumogastric nerve. Hence increased secretion of the digestive juices, augmented appetite, more active peristalsis, and improved digestion, to which, indeed, the direct action of alcohol upon the cerebrum doubtless contributes. It is to these effects that the favorable influences of this agent in the extremes of life, when it is so well borne and so useful, must be largely attributed.