Experiments show that alcohol retards digestion in vitro, but we cannot conclude from this that a moderate quantity of it has a similar effect in the living stomach : in this case we have to take into account not only its influence on ferment action, but also on secretion and on the movements of the stomach. We can, indeed, only judge of its action on digestion by experience, and experience shows that, in many cases at least, a sound alcoholic beverage taken in moderation does not appreciably injure digestion, while in the feeble and delicate it may promote the process, both by its psychic effect and by its more direct action on the gastric mucous membrane.
But whatever view be held as to the effect on digestion of a moderate quantity of a sound alcoholic drink, it is certain that when taken immoderately, or in impure forms, alcohol upsets digestion and leads in course of time to degenerative changes in the whole of the alimentary tract. Most conspicuous among these is catarrh of the mucous lining. This leads to an excessive outpouring of mucus and to a gradual atrophy of the epithelium, with concomitant fibrosis.
The mucus being thus in excess and the digestive juices at the same time deficient, not only is normal digestion interfered with, but the development of saprophytic organisms is favoured : the alimentary tract in consequence becomes a veritable laboratory for the manufacture of poisons which, rushing the defences provided by the alimentary mucous membrane and the liver, gain entrance into the blood, and thus set up a condition of "indigestion toxaemia," as we may term it. Dr. Ford Robertson contends that it is to this secondary toxaemia, rather than to the alcohol itself, that the degenerative changes of chronic alcoholism are mainly due.
That the absorption of poisons from the alimentary tract may cause widespread tissue-degradation there can be no doubt. Now the more perfect the digestion in stomach and bowel, but especially in the latter, the less is the tendency to indigestion toxaemia and to the consequent degeneration of the tissues at large; and it is therefore not surprising that centenarians generally give a history of sound digestion. Metchnicoff has suggested that the absorption of poisons from the large bowel plays a prominent part in bringing about senility. Whether or not this is the case there can be no doubt that the living organism does not simply wear out, but that it becomes senile - just as it becomes adolescent - essentially by the operation of definite vital mechanisms, though what, precisely, those mechanisms are we do not yet know. Probably the absorption of poisons from the alimentary tract - though rather, we would suggest, from the small than the large bowel - is one, but only one, among many such mechanisms. The view that the possession of a colon is an important factor in the induction of senility has, in our opinion, obtained wider circulation and credence than it deserves, but be this as it may, it is certain that sound digestion promotes sound nutrition and therefore tends to delay the onset of senile decay, while it is equally certain that the abuse of alcohol, by disturbing digestion and thus inducing toxaemia, favours its premature occurrence.
The well-known "morning sickness" of the drunkard is due to gastritis. His gastric indigestion results not only from disease of the gastric mucous membrane, but also from atony of the muscular coat of the stomach, in consequence of which the food tends to linger in it unduly. A similar atony may affect the bowel.