GASTRIC JUICE. 31 



an experimental investigation into the properties of the gastric 

 juice. They start with the assumption that this fluid owes its 

 digestive properties to the union of two principles : 1st, an acid ; 

 2d, a peculiar organic matter destructible by heat. What is 

 the nature of the acid ? " The principal fact which has been 

 adduced to prove that the acid reaction is owing to the presence 

 of biphosphate of lime is, that it may be treated with carbonate 

 of lime without effervescence. Our experiments show that this 

 arises from the dilution of the acid, which allows the carbonic 

 acid to be dissolved as it is formed. When, therefore, the 

 gastric juice is concentrated, it causes a considerable effer- 

 vescence with chalk. Moreover, gastric juice dissolves neutral 

 phosphate of lime, whilst this salt is entirely insoluble in a solu- 

 tion of the biphosphate. On distilling gastric juice, the first 

 distillate exhibits no acid reaction. If a mere trace of acetic 

 acid or acetate of soda is added previous to distillation, it gives 

 an acid reaction ; the normal acid is not therefore acetic. This 

 also appeared, at first sight, to prove it could not be hydro- 

 chloric acid; but on distilling water rendered slightly acid by 

 hydrochloric acid, nothing passes over at first but pure water, 

 the acid not distilling until the end of the operation. On dis- 

 tilling gastric juice a neutral limpid liquor passes over, which 

 is not precipitated with nitrate of silver; when about four 

 fifths has distilled over, the distillate is perceptibly acid, 

 nevertheless, it does not render a solution of nitrate of silver 

 turbid ; but at the end, and when only a few drops of the gas- 

 tric juice remain in the retort, an acid liquid passes over which 

 precipitates sa]ts of silver ; this is, doubtless, hydrochloric acid. 

 Does this acid exist free in gastric juice, or has a chloride been 

 decomposed in this operation ? When the least trace of oxalic 

 acid is added to gastric juice which we know contains lime, a 

 turbidity is produced from the formation of an insoluble oxalate 

 of lime ; but if to water acidified with SOOOths of its amount of 

 hydrochloric acid, and containing chloride of lime, the same re- 

 agent be added, no turbidity ensues. This clearly proves that 

 hydrochloric acid exists as a chloride in the gastric juice, and 

 not in a free state. 



When concentrated by evaporation, gastric juice is strongly 

 acid, effervescing with chalk, and not loosing its acid reaction 

 in the presence of an excess of the chalk. This proves the pre- 



