nary manner, or directly introduced into the organ. This fact was established by experiments in the case of Alexis St. Martin, of which Dr. Beaumont availed himself with so much industry and judgment. A permanent aperture had been made into this person's stomach by a gunshot wound in the side, which allowed its interior to be seen, its contents to be taken out and examined, and foreign matters to be directly conveyed into it. The following are among the experiments adverted to.

"To ascertain whether the sense of hunger would be allayed without the food being passed through the œsophagus, St. Martin fasted from breakfast-time till four o'clock, P.M., and became quite hungry. I then put in at the aperture, three and a half drachms of lean boiled beef. The sense of hunger immediately subsided, and stopped the croaking noise caused by the motion of the air in the stomach and the intestines, peculiar to him since the wound, and almost always observed when the stomach is empty.

"At one o'clock, another day, St. Martin complaining of being quite hungry, I put into the stomach, at the aperture, twelve raw oysters, more than middling size. The sensation was allayed, and the appetite satisfied, the same as if swallowed."

Consistently with these curious facts, it is well known that the natural disposition of a very hungry person is to chew hastily and imperfectly, and to bolt his food. He is not satisfied till the food reaches

his stomach. Food, however, when insufficiently masticated, and swallowed in large and hard masses, is liable to injure the oesophagus in going down, and when it reaches the stomach, is difficult of digestion. One purpose of the senses of taste and flavour which we enjoy, is to induce us to continue comminuting the food in the mouth, and bruising it as long as its taste and flavour last; while we are gratifying these senses, the food acquires the requisite consistence for easy swallowing and easy digestion. The time gained by this process prevents the stomach being too rapidly filled, and allows the appetite to be satiated before the stomach is overloaded.

The substances introduced into the stomach are in reference to their consistence either innutritious liquids, or liquids with food mixed, or solids. The first are quickly absorbed and carried out of the stomach; the second undergo a separation of the liquid; after which the solider part, like ordinary solid food, is digested.

The process of digestion is strictly chemical. It is the result of the action of a solvent fluid upon the aliment, and takes place almost equally well without as within the body, if the proper temperature is maintained.

The solvent fluid is poured out by the lining membrane of the stomach, as the perspiration pours off the surface of the body. It is called the gastric*

*

Taorηp, the stomach; gastric, belonging to the stomach.

uice. It consists of water holding in solution free muriatic and acetic acids, phosphates and muriates with bases of potassa and soda, magnesia and lime, and an animal matter soluble in cold water, but insoluble in hot. It is clear and transparent, inodorous, a little saltish, and very perceptibly acid. It does not exist constantly, or accumulate in the stomach: but it is only secreted when wanted, or when the stomach is excited by the introduction of new matter into it.

The solvent power of the gastric juice out of the body was ascertained by Spallanzani, and Mr. Hunter discovered the remarkable phenomenon, that it would even digest, after death, the stomach which formed it. Dr. Beaumont, by many experiments, has confirmed the conclusions of Spallanzani. In some of the most valuable which he narrates, the "changes in the same meal were observed, while part of it was undergoing digestion in the stomach, part in a phial of gastric juice obtained at the same time from the same stomach, and maintained at the temperature of 100° by immersion in hot water. The effect of the gastric juice on the piece of meat introduced into the stomach, was exactly similar to that in the phial, only more rapid (from the addition doubtless of more gastric juice) after the first half hour, and sooner completed. Digestion commenced on, and was confined to, the surface in both situations. Agitation accelerated the solution in the phial, by removing the coat that was digested on the surface, enveloping the

remainder of the meat in the gastric juice, and giving the fluid access to the undigested portion."

The dissolved food, or the chyme, has the appearance of a thick homogeneous liquid, the colour of which partakes slightly of the colour of the food eaten. It is always of a lightish or grayish colour; varying in its shade and appearance from that of cream, to a grayish or dark-coloured gruel. Chyme from butter, fat meats, oil, resembles rich cream. All chyme is acid.

The perfectness of digestion (the food being digestible, and the stomach in health,) is dependent on the quantity of the gastric juice; if the quantity of the latter is proportionate to the meal which has been taken, the whole is changed into chyme. If the quantity of gastric juice is insufficient, a residue of undigested food remains in the stomach, and becomes a source of irritation and derangement of function. It is not necessary that the stomach should be emptied of one meal before another is introduced into it. The presence of a second meal, crude and fresh, does not necessarily disturb the digestion of the first. If the stomach is in full vigour, and can furnish the absolute quantity of gastric juice required for both, both meals will undergo together harmonious digestion.

II. OF FOOD.

OUR food, it has been already remarked, consists of solid and liquid,-the former intended to be changed

into chyme, the latter to be absorbed at once, and carried into the circulation, to make up for the waste of fluids which continually takes place. The distinction, however, is not a rigorous one. The food which we introduce into the stomach, is a very soft and moist solid, either from its own nature or from having been mixed with the saliva or other liquids; and the liquid which we drink for the primary object of allaying thirst, is often qualified by the addition of nutritive matter, or of some stimulating principle.

The substances which we consume as food are borrowed from the animal or vegetable kingdoms. Their essential ingredients are certain chemical principles, fibrin, albumen, gelatin, oil, gluten, sugar, singly or in combination. Different as are these elements, it is probable, that the ultimate principle of nutriment is always the same, from whatever source obtained. It was said by Hippocrates that there are many kinds of aliment, but that there is at the same time but one aliment. Nothing has been proved in modern physiology or chemistry to invalidate this opinion.

Dr. Franklin told Dr. Stark that when a journeyman printer, he lived for a fortnight on bread and water, at the rate of ten-pennyworth of bread per week, and that he found himself stout and hearty with this diet.

Sir John Pringle told the same author that he knew a lady, then ninety years of age, who ate only the pure fat of meat.