Spallanzani1 and Reaumur were the first to make experimental studies upon the gastric juice. They recognized its property of digesting meat and of exerting an antifermentative action. Prout in 1824 discovered hydrochloric acid in the gastric juice. These experiments have been greatly furthered and advanced in this country by Beaumont,2 who at about the same time made a series of investigations upon the well-known Canadian St. Martin with his gastric fistula. Many of the facts discovered by Beaumont form the basis of our knowledge of the physiology of the stomach; as, for instance, his observations on the movements of the stomach. Blondlot1 first established a gastric fistula in animals for experimental purposes. Bidder and Schmidt2 have conclusively shown that the acid of the gastric juice is hydrochloric acid, while Schwann in 1836 discovered the pepsin ferment. The nature of the acid of the gastric juice has been the subject of much controversy even during late years. Thus Winter and Hayem3 disputed the formation of hydrochloric acid within the gastric glands. They assert that while the glands produce an organic acid, this is changed into an inorganic by the presence of salt (sodium chloride) within the stomach.

This theory, however, is incorrect, as it is well known that the stomach will furnish a secretion containing free hydrochloric acid even when no food or other substance containing sodium chloride has been ingested.

1Spallanzani. "Versuche fiber das Verdauungsgeschaft," Ab-handlung vi.

2 Beaumont: "Experiments and Observations of the Gastric Juice and the Physiology of Digestion," Combe's edition, 1883.

The gastric juice is a clear, colorless fluid of an acid reaction and a specific gravity of 1.002-1.003. The quantity secreted in twenty-four hours is not exactly known. It is estimated by some to be about three pints. The principal constituents of the gastric juice are: (1) Hydrochloric acid; (2) pepsin; (3) rennet. Recently a fat-splitting ferment has been discovered in the gastric juice by Volhard.4

1 Blondlot: "Traite analytique de la digestion," Paris, 1843. 2Schmidt: Liebig's Annalen. xcii., 1854.

3 Winter and Hayem: "Du Chimisme Stomachale," Paris, 1891. 4Franz Volhard: "Ueber das fettspaltende Ferment des Magens." Zeitsehr. f. klin. Med.. Bd. 43 Heft .5 und 6.

The degree of acdity rarse from 0.l to 0.3 per cent. Both ferments, pepsin and rennet, when first secreted are inactive bodies and called respectively pepsinogen and rennet-zymogen, but coming in contact with the acid become converted into active pepsin and rennet. Besides these three substances, the gastric juice contains water, inorganic salts, and some proteid matters.

The greatest difficulty in explaining the production of gastric juice was encountered in the circumstance that an inorganic acid should be secreted by the blood, which is a strongly alkaline solution. Maly,1 however, gave the following explanation: Some liquids with alkaline reaction may contain acid salts; thus in the blood there exist disodic orthophospbate and monosodic orthophosphate (Na.HP04 and NaH2PO), together with distinctly alkaline salts. When such a solution is placed into a dialyzer immersed in distilled water the acid principle passes into the latter. Thus within the dialyzer there is an alkaline and outside an acid liquid. Maly compares the stomach and the kidneys to a dialyzer, and explains in this way the secretion of acid fluids from the kidnevs and from the stomach. The details of the formation of hydrochloric acid may be given as follows: If Na2HPO4 is brought together with calcium chloride (CaCl,), there is formed triphosphate of calcium, sodium chloride, and free hydrochloric acid according to the following formula: 2Na2HPO4 + 3CaCl2 = Ca2(P04)2 + 4NaCl + 2HC1.

This theory, although very ingenious, does not suffice to explain the entire process of gastric secretion. For there is no reason why the hydrochloric acid should not be secreted in other organs than the stomach, the blood coming into contact with many other glandular apparatuses. Besides, this theory does not explain why the secretion should not go on all the time in the stomach. Here as elsewhere we are forced to accept a specific action of the cells which cannot be explained by simply physical or chemical laws. We know that there are cells imbued with certain specific actions that are unexplainable by chemical formula.

1 Maly: "Unterouchungen fiber die Mittel zur Saurebildung ira Organismus." Zeitschrift fur physiologische Cheraie, i., p. 174.