THE HISTORY OF DIETETICS 421 



mechanism of gastric digestion were held l)y tlie rival physical and 

 chemical schools of tliat period. The chemical tiieory 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 trituration 

 of 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 diges- 

 tion and regarded the Avhole process as purely mechanical. 



During the eighteenth century the only additions to the knowledge 

 of digestion were a few studies of the gastric juice. 



Rene 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 Spallan- 

 zani (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 nine- 

 teenth century. Si^allanzani 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 experi- 

 ments 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 



