THE PHYSIOLOGY OF DIGESTION 175 



Previous to this time various theories of digestion were based upon 

 obscure ideas of trituration, concoction, fermentation and putrefaction 

 or whatever these words might imply. Difficult as it is for us to-day 

 to reproduce the point of view of men who were " struggling with the 

 spiritualistic fermentations of van Helmont, on the one hand, and with 

 the material effervescences of Sylvius, on the other," we can neverthe- 

 less appreciate the remark of William Hunter: 



Some physiologists will have it, that the stomach is a mill, others, that it 

 is a fermenting vat, others, again, that it is a stew-pan; but, in my view of the 

 matter, it is neither a mill, a fermenting vat, nor a stew-pan; but a stomach, 

 gentlemen, a stomach. 



The third epoch in the study of the physiology of digestion coin- 

 cides with the rise of modern chemistry and may, perhaps, be said to 

 start with the discovery of free hydrochloric acid in the gastric juice 

 by Prout and by Tiedemann and Gmelin in 1824, soon followed by the 

 pioneer work of Dr. "William Beaumont upon Alexis St. Martin. Fos- 

 ter writes: 



It was left for the nineteenth century to throw a new light on the nature 

 of the gastric changes and at the same time shew that what took place in the 

 stomach was not the whole of digestion, but only the first of a series of pro- 

 found changes taking place along nearly the whole length of the alimentary 

 canal. 



Let us bear in mind, then, that although the presence of a solvent 

 fluid in the stomach had begun to be admitted in 1803, its nature and 

 the mode of its operation were not understood until Beaumont's classic 

 experiments (1833) on "the man with a lid on his stomach," as St. 

 Martin was derisively called. Eeaumur (1753) experimented on a 

 buzzard, administering to it hollow metallic capsules perforated like a 

 sieve and containing foods within. The possibility of mechanical 

 crushing or trituration was thereby excluded ; but when the tubes were 

 regurgitated it was found that digestion (solution) of the food mate- 

 rials had nevertheless taken place. Some chemical action must have 

 been exerted; and by placing sponges in the metallic tubes, Eeaumur 

 was able to express therefrom specimens of gastric fluid. He appre- 

 ciated that it possessed properties antagonistic to putrefaction; and 

 fragmentary as his observations may appear, he introduced a- new 

 method into physiological research. To Spallanzani was left the exten- 

 sion of these investigations in most fruitful fields. He well recognized 

 the antiseptic power of the gastric secretion. With regard to the 

 nature of digestion Spallanzani concluded (1783) in these words: 



None of the three forms of fermentation distinguished by chemists under 

 the name of spirituous (alcoholic), acid, or putrid, have any place in digestion. 



His well-conceived experiments in which animals swallowed meat 

 attached to strings by which it could be withdrawn from time to time, 



