218 The Physiology of Digestion [lect. 



mouth after a too great indulgence in strawberries and white 

 wine, which had obviously disagreed with him. 



It will be interesting to quote here what is perhaps the 

 earliest analysis of gastric juice. Spallanzani asked his colleague 

 and friend, Scopoli, Professor of Chemistry at Pavia, to examine 

 for him the gastric juice which he had obtained from crows 

 by his sponges and tubes. This is what the chemist reports. 

 "The fluid contains first pure water, secondly a saponaceous 

 " and gelatinous animal substance, thirdly sal ammoniac, and 

 " fourthly an earthy matter like that which exists in all 

 "animal fluids. It precipitates silver from nitrous acid and 

 " forms luna cornea. This phenomenon might induce us to 

 M suppose that common salt exists in the gastric juice ; but 

 " the salt contained in this fluid is not common salt, but 

 " sal ammoniac." 



Spallanzani thus came to the conclusion that gastric juice 

 is not acid, though he asked himself the question whether 

 since it curdled milk it might not contain "an acid in some 

 " latent form." 



Since then gastric juice was not acid, solution of food by 

 its means could not be of the nature of acetous fermentation 

 any more than it was of the nature of vinous or putrid 

 fermentation. It was not any of the known forms of ferment- 

 ation ; it was not a fermentation at all. 



We thus owe to Spallanzani, after Keaumur, the definite 

 experimental proof of the solvent power of gastric juice over 

 various constituents of food. But he was unable to go beyond 

 this, because he failed to recognize its acid character; he 

 could only say that the action was not a fermentation in the 

 then usual sense of that word ; he could not explain how this 

 apparently neutral fluid possessed these solvent powers. We 

 may wonder how so acute an observer missed the acidity of 

 gastric juice. We may partly explain this by the fact that he 

 confined his tests for acidity to the gastric juice which he had 

 obtained from fasting stomachs, including that obtained from 

 himself, and apparently did not test the juice which had 

 actually digested the material contained in his tubes. Still 

 in some or other of his almost innumerable experiments he 



