As I have elsewhere observed, various are the theories that have been entertained in regard to digestion, but the experiments of Dr. Beaumont seem to have proved beyond a doubt, that this operation is due to the action of the gastric juice, with which he was enabled to produce artificial digestion. Having obtained one ounce of this solvent from the stomach of his patient, he put into it a solid piece of recently-boiled beef, weighing three drams, and placed the vessel that contained it in a water bath heated to 100 deg. In forty minutes digestion had commenced on the surface of the meat; in fifty minutes, the fluid was quite opake and cloudy, the external texture began to separate and become loose; in sixty minutes, chyme began to form. At 1 p.m. (two hours after the commencement of the experiment), the cellular substance was destroyed, the muscular fibres loose and floating about in fine small threads very tender and soft. In six hours they were nearly all digested--a few fibres only remaining. After the lapse of ten hours, every part of the meat was completely digested. The artificial digestion by these experiments appears to be but little slower than the natural process--they also demonstrate the influence of the temperature, and the quantity of the solvent secretion. Having obtained from St. Martin two ounces of gastric juice, he divided this quantity into two equal portions, and laid in each an equal quantity of masticated roast beef. One he placed in a water bath at the temperature of 99 deg. Farh.--and left the other exposed to the open air at the temperature of 34 deg.; a third similar portion of meat he kept in a phial, with an ounce of cold water. An hour after the commencement of the experiment, St. Martin had finished his breakfast, which consisted of the same meat with biscuit, butter, and coffee. Two hours after the meat had been put into the phial, the portion in the warm gastric juice was as far advanced in chymification as the food in the stomach; the meat in the cold gastric juice was less acted on, and that in the cold water only slightly macerated. In two hours and forty-five minutes from the time that the experiment was begun, the food in the stomach was completely digested, the stomach empty, while even at the end of six hours the meat in the gastric juice was only half digested. Dr. Beaumont, therefore, having procured 12 drams of fresh gastric juice, added now a portion to each of the phials containing meat and gastric juice, and to a portion of the half-digested food which he had withdrawn from the stomach two hours after the commencement of the experiment, and which had not advanced towards solution. After eight hours' maceration, the portions of meat in the cold gastric juice, and in the cold water, were little changed, but, from the time of the addition of the fresh gastric juice, digestion went on rapidly in the other phials, which were kept at the proper heat, and at the end of