To discover what influence would be exerted on food masticated, swallowed, and mixed with the gastric juice in the usual way, and then withdrawn from the stomach, Dr Beaumont gave St Martin an ordinary dinner of boiled salted beef, bread, potatoes, and turnips, with a gill of pure water for drink; and twenty minutes afterwards drew off through the opening about a gill of the contents of the stomach into an open mouthed vial. In this short space of time digestion had already commenced, thus negativing the common notion that an hour elapses before it begins. The vial was now placed in a water-bath, at a temperature of 100°, and continued there for five hours. Examined at the end of that time, the whole contents were found to be dissolved. On then extracting an equal quantity of chyme from the stomach, and comparing it with the solution in the vial, little difference was observable between them, except that the process had been somewhat more rapid in than out of the stomach. But this experiment is remarkable in another point of view, as shewing that in the short space of twenty minutes enough of gastric juice had been secreted for the entire completion of digestion.
With a view to verify these results, and also to discover the comparative digestibility of different kinds of aliment, Dr Beaumont gave St Martin for dinner eight ounces of recently-salted lean beef, four ounces of potatoes, some bread, and four ounces of boiled turnips. After fifteen minutes he withdrew a portion of the contents of the stomach, and found that some of the meat had already been slightly digested. In a second portion, withdrawn at the end of forty-five minutes, fragments of the beef and bread were perceptible, and in a still more advanced state of digestion; the meat was in small shreds, soft and pulpy, and the fluid containing it had become more opaque and gruel-like in appearance. When two hours had elapsed, a third quantity was taken out, at which time nearly all the meat had become chymified and changed into a reddish-brown fluid; but small pieces of vegetable matter now presented themselves for the first time, but in a state of digestion so much less advanced than the meat, that their peculiar structure was still distinctly visible. Some of the second and third portions, put into a vial and treated in the usual way, advanced to complete digestion, as in the other experiment, except that the process was slower, and that a few vegetable fibres remained to the last undissolved; thus confirming the general opinion that vegetables are more difficult of digestion than animal substances.
The mode of solution by the gastric juice varies according to the nature of the food on which it acts. We have seen that it gradually reduces solids to a soft and fluid state; but its effect on milk and albumen is different. It begins by coagulating them so as to give them the requisite consistence for being affected by the muscular contractions of the stomach, and impregnated with the juice. Fifteen minutes after St Martin had drunk half a pint of milk, a portion taken out of the stomach by Dr Beaumont presented the appearance of a fine loosely-coagulated substance, mixed with a semi-transparent whey-coloured fluid. A drachm of warm gastric juice poured into two drachms of milk, at a temperature of 100°, produced a precisely similar appearance in twenty minutes. In another experiment, when four ounces of bread were given along with a pint of milk, and the contents were examined at the end of thirty minutes, the milk was coagulated, and the bread reduced to a soft pulp floating in a large proportion of fluid. In two hours the whole was digested.
When the white or albumen of two eggs was swallowed on an empty stomach, small white flakes began to be seen in about ten or fifteen minutes, and the mixture soon assumed an opaque whitish appearance. In an hour and a half the whole had disappeared. Two drachms of albumen, mixed with two of gastric juice out of the stomach, underwent the same changes, but in a rather longer time.
When the food is chiefly liquid, as when soup is taken either alone or in large proportion, the more fluid part is speedily absorbed, to fit the remaining nutritious portion for being better acted on by the gastric juice and muscular power of the stomach; but in impaired digestion, the requisite absorption of the fluid part does not go on so rapidly. Fifty minutes after St Martin had dined on vegetable soup, beef, and bread, Dr Beaumont found the stomach to contain a pulpous mass, like thick gruel in consistence, and of a semi-gelatinous aspect. The fluid portion had been absorbed to such an extent, that the remainder was even thicker than is usual after eating more solid food. From many similar observations, Dr Beaumont infers it to be a general law, that soups and liquids cannot be digested till they are formed into a thicker mass by the absorption of their watery part—as till then they are too liquid to be easily acted on by the gastric juice. Hence their unfitness for weak stomachs, and the impropriety of large libations of tea or coffee at breakfast by persons whose digestion is bad. During recovery from illness, chicken-tea, beef-tea, and soups, are often useful, simply because the system then requires the liquid to make up its lost blood.
Unfortunately Dr Beaumont made few experiments on the action of gastric juice upon vegetables; and, in the few recorded, he generally contents himself with noting the length of time required for their solution, which generally proved considerably longer than for animal substances. In one experiment, however, he states, that an hour after giving St Martin nine ounces of raw, ripe, sour, apples, the stomach was full of fluid and pulp, “quite acrid, and irritating the edges of the aperture, as is always the case when he eats acescent fruits or vegetables.” In an hour and a half the contents were still more sharp and acrid, and the pulp of the apple visible. At the end of two hours the stomach was empty, but the mucous membrane exhibited an irritated appearance. With farinaceous vegetables, however, the results were different. Thus, when a pint of thick, rich, boiled sago, sweetened with sugar, was given, the whole was digested in less than two hours, and there was neither acrimony of the gastric contents nor smarting of the edges of the wound; on the contrary, it seemed peculiarly grateful to the stomach, and rendered the mucous membrane soft, uniform, and healthy. The same results followed a repetition of the experiment, and also when a pint of soft custard was taken. In some states of the stomach, it is true, even farinaceous food excites acrimony and irritation, but rarely in the same degree as the other forms of vegetable aliment.
Such being the influence of gastric juice on different aliments at the natural heat of the body, we have now to ascertain, in the SECOND place, what share the high temperature has in the result.
To determine this point, Dr Beaumont took out two ounces of gastric juice, and divided it into two equal portions, in separate vials. He added to each an equal weight of masticated fresh beef; and placed the one in a bath at the temperature of 99°, and the other in the open air at 34°. As a contrast to these, he placed beside the latter a third vial, containing the same weight of masticated meat in an ounce of clear water.
In two hours the meat in the warm vial was partially digested; that in the cold gastric juice was scarcely changed; and the third portion, in the cold water, seemed only a little macerated. In six hours the meat in the warm vial was half digested, while that in the two others had undergone no farther alteration. The gastric juice in the first vial having by this time dissolved as much as it could of the beef, four drachms more were added from the stomach, and the vial was replaced in the bath. Digestion, which had previously ceased, was now resumed, and went on as steadily as if it had not been interrupted; thus shewing, in a striking manner, the impropriety of exceeding in our meals the quantity for which alone a sufficiency of gastric juice can be provided.