44 GASTRIC JUICE. 



We have already stated all that need be said regarding the 

 comparatively rare occurrence of hydrofluoric, acetic, and butyric 

 acids in the gastric juice, in our remarks on those acids in the 

 first volume : we have only to add that Frerichs has recently 

 succeeded in detecting butyric acid in the stomach of a fasting 

 horse and of a fasting sheep, thus confirming the earlier experi- 

 ments of Tiedemann and Gmelin. 



In regard to the free acid in the gastric juice, 1 may observe 

 that in six experiments in which I dried the gastric juice in vacuo, 

 and intercepted the hydrochloric acid which was evolved (see vol. 

 i. p. 93), I found it to vary from 0*098 to 0'132; and I then found 

 from 0-320 to 0'583 of free lactic acid in the residue; so that if 

 lactic acid had been the only free acid in the gastric juice (that is 

 to say, if the acidity had depended on that acid alone) it would 

 have ranged from 0-561 to 0'908. 



It is not at all improbable that the quantity of free acid in the 

 gastric juice is as variable as that of the alkali in the saliva ; any 

 one, however, who has occupied himself with experiments of this 

 nature, will see that these numbers can only give an approximative 

 idea regarding the quantity of acid in the gastric juice; for, 

 independently of the circumstance that the fluid collected from a 

 gastric fistula is never obtained in a state of entire purity, the 

 methods adopted for exciting the flow of the secretion exert an 

 essential influence on its constitution. The gastric juice used in 

 my experiments was collected from three dogs at very different 

 times, after they had fasted for twelve hours. I gave them fatty 

 bones, and collected the gastric juice in from 10 to 25 minutes 

 afterwards ; it was only by the repetition of the process that I 

 could gradually collect a quantity of gastric juice sufficient for 

 analysis, so that each of the six determinations may be regarded as 

 giving a mean result. I determined the whole amount of the free 

 acid of the filtered gastric juice, by saturating it with carbonate of 

 baryta, and then calculating the quantity of free lactic acid from 

 the sulphate of baryta precipitated by sulphuric acid. 



Blondlot,by some erroneous process, was induced to believe that 

 gastric juice did not decompose carbonate of lime, and was hence 

 led to conclude that the acid reaction of the gastric juice depended 

 solely on the acid phosphate of lime; Dumas, Melsens, and Ber- 

 nard have found that not only the carbonate but also the basic 

 phosphate of lime is soluble in gastric juice, as also are even zinc 

 and iron, hydrogen being simultaneously developed properties 

 which a solution of acid phosphate of lime does not possess. 



