Page:Popular Science Monthly Volume 83.djvu/425

Rh mechanism of gastric digestion were held l)y the rival physical and chemical schools of that period. The chemical theory of digestion was that of van Helmont, Sylvius, and their followers. On the other hand, Alfonso Borelli (1608-1679), the founder of the iatro-physical school, held that gastric secretion was chiefly effected by powerful triturationof the ingested food by the muscular walls of the stomach, as appears especially in birds; and while he conceded a corrosive action of the stomach juices in some species, his followers denied all chemical digestion and regarded the whole process as purely mechanical.

During the eighteenth century the only additions to the knowledge of digestion were a few studies of the gastric juice.

René Antoine Ferchault de Reaumur (1683-1757) developed a new and fruitful method of investigation, publishing his results in 1753. He introduced metal tubes containing various food materials into the stomach of a buzzard (which, like other carnivorous birds, ejects from the mouth indigestible substances like bones, etc.) and other animals, and on examining them subsequently was able to determine the effect of the gastric juice on these materials. By using sponges in the tubes he was the first to obtain gastric juice in pure condition. He observed that meat and bone were dissolved by the gastric juice, but not grains or flour. He thus demonstrated that this secretion possessed a definite solvent power, distinct from putrefaction, and independent of trituration.

Employing Reaumur's and other similar methods, Lazaro Spallanzani (1729-1799), of Italy, continued and extended the observations, publishing his results in 1777 and subsequently. In 1777 Stevens, of Edinburgh, published a similar research. John Hunter (1728-1793) in 1773 and 1786 also published some observations on digestion.

The acidity of the gastric juice, appreciated by van Helmont and denied by his successors, was not generally recognized until the nineteenth century. Spallanzani and Hunter regarded the acidity of some of the specimens which they obtained as occasional or exceptional or abnormal only. Carminati recognized the real conditions, showing in 1785 that the gastric juice while fasting is neutral, and is acid only after taking food; his observations, however, did not gain general attention,

A contribution of interest to Americans, which, however, passed unnoticed, was the graduation thesis of John R. Young, of Maryland, at the University of Pennsylvania in 1803, in which he described experiments made on digestion in the stomachs of frogs and human subjects, and demonstrated the acidity of the gastric juice.

The foundations of our present knowledge of digestion were mainly established during the second quarter of the nineteenth century.

William Prout (1785-1850), of London, in 1834 identified the acid principle of the gastric juice as hydrochloric acid.

William Beaumont (1785-1853), an American army surgeon, from 1825 to 1833 conducted a celebrated series of observations of gastric