CHAP. XXIV.] THE GASTRIC JUICE. 205 



because he employed a too much diluted fluid : on concentrating 

 the gastric juice a little, the effect was readily produced. Ad- 

 mitting that a free acid is present, they deny that it is hydrochloric 

 acid, because that acid exists in the gastric fluid only in the state 

 of chloride. If a minute quantity of oxalic acid be added to the 

 gastric juice, a precipitation is occasioned by the formation of in- 

 soluble oxalate of lime, whilst an equal quantity of the same re- 

 agent, added to distilled water containing a two-thousandth part of 

 hydrochloric acid, to which chloride of lime had been added, pro- 

 duced no such effect. The lime of the gastric juice unites with the 

 oxalic acid ; but that acid will not displace lime from its connexion 

 with hydochloric acid. Nor is the acid of the gastric juice free 

 acetic acid ; the most delicate tests failed to detect it. MM. Bernard 

 and Barreswil infer that there is in the gastric fluid a minute propor- 

 tion of phosphoric acid, which, however, is not the only free acid. 

 The lactic acid, according to these observers, is the principal acid 

 of the gastric juice, because the behaviour of a fluid acidulated with 

 that acid corresponds very exactly under chemical examination 

 with that of the gastric juice. Thus the distillation of water aci- 

 dulated with lactic acid exhibits exactly the same stages as that of 

 the gastric fluid, first, there passes over only pure water, in the 

 next stage an acid liquid, in which salts of silver do not throw down 

 a precipitate, and there remains a strongly acid fluid effervescing 

 with carbonates ; in this remaining liquid, hydrochloric acid may 

 be detected if a minute quantity of chloride of sodium had been 

 added to the fluid previous to distillation. 



The acid of the gastric juice produces salts of zinc, lime, baryta, 

 and copper, similar to those formed by lactic acid ; and MM. Ber- 

 nard and Barreswil affirm that it readily decomposes the chlorides 

 in concentrated solutions. Hence it is that hydrochloric acid 

 passes over in the last products of the distillation of the gastric 

 juice. 



These authors also state, that the nature of the food appears to 

 exercise no influence upon the nature of the acid, and that they 

 have always found free lactic acid, whether after an exclusive 

 vegetable or animal regimen continued for many days, or after a 

 prolonged very sparing diet. 



Dr. R. D. Thomson, of Glasgow, in a paper published in 1845, 

 also disproves the opinion of Blondlot by experiment, and comes 

 to the conclusion that the free acid of the stomach, in the digestion 

 of vegetable matter at least, of all the known acids corresponds 

 only with the lactic. 



