But the effects of direct mechanical pressure are not the only ones. The accumulations in the colon necessarily arrest the free passage of the product of the small intestine, and that, in turn, causes undue retention of food in the stomach, with consequent fermentation; while the irritation, due to pressure on the nerve terminals by the distension, and by the encrusted matter adhering to the intestinal wall, is simply incalculable.
The effects of gaseous accumulations in the alimentary canal are not thoroughly understood at present--that is--the pathological effects. The more direct effects, as manifested in abdominal distension, and the terrible distress that frequently follows eating, are unfortunately, but too well known. The reader does not need to be told that during the decomposition of organic substances, gases are evolved, and no matter where the process goes on, the results are always the same. Owing to the causes previously mentioned, the intestinal canal usually offers special facilities for the production of gases, owing to the retention of partially digested food, in a medium highly favorable to fermentation. A moderate amount of sulphuretted hydrogen, and also carburetted hydrogen is always present in the colon, normally, to preserve moderate distention of the walls, while the gases usually found in the stomach and small intestine, are oxygen, hydrogen, nitrogen and carbonic acid. What functional disturbances may arise from the presence of these gaseous substances in excess in the system is, at present, largely a matter of conjecture, but it _is_ known that a stream of carbonic acid gas, or hydrogen continuously directed against a muscle will cause paralysis of that structure. The expansive force of gases is too well known to need comment, and the force with which they will at times distend the abdominal wall points irresistibly to the conclusion that such an amount of force exerted against vital organs cannot be otherwise than productive of serious harm. It is not at all improbable that many cases of hernia and uterine displacement may be due to this hitherto unsuspected cause. That they penetrate the neighboring tissues is an established fact, and it is quite conceivable that their action upon the nervous system though the medium of the circulation may lie at the root of many of the cases of neurasthenia that are now so prevalent.