SOUKCE OF THE ACIDITY OF THE GASTBIC JUICE. 237 



secreting stomachs of calves as they were killed, from six to 

 ten pints of gastric juice ; and from this he extracted the 

 pure pepsin by the process recommended by Payen, which 

 consists merely in one or two precipitations by alcohol. This 

 substance he found to be identical with the principle obtained 

 by Payen from the gastric juice of the dog. Its action upon 

 albuminoid matters was precisely the same as that of pepsin 

 extracted from artificial gastric juice, except that it was 

 more powerful. 



Source of the Acidity of the Gastric Juice. Reaumur 

 and Spallanzani recognized that the fluid from the stomach 

 has, at certain times, an acid reaction ; and subsequent ob- 

 servations have confirmed this fact, and shown that this re- 

 action is invariable during digestion. But although the most 

 distinguished and skilful chemists of the day have attempted 

 to ascertain the source of this acidity, from Prout, in 1823, 

 to Blondlot, in 1858, embracing Leuret and Lassaigne, Tiede- 

 mann and Gmelin, Berzelius, Chevreuil, Bidder and Schmidt, 

 Dumas, Lehmann, Bernard and Barreswil, with a host of 

 others, the question has not yet received a solution which is 

 generally accepted. It would be inconsistent with the plan 

 of this work to discuss all the opinions which have from time 

 to time been expressed upon this subject, or to attempt to 

 criticise the various processes employed by different chemists 

 in the analyses they have brought forward in support of their 

 views. The discussion will be confined to the question of 

 the existence of one or more of three acid principles ; viz., 

 free hydrochloric acid, free lactic acid, and the acid phos- 

 phate of lime. 



In 1823, Prout examined the fluid from the stomachs of 

 rabbits which had been fed a short time before death, and 

 demonstrated, apparently, the presence of free hydrochloric 

 acid. The method employed in these analyses was to estimate 

 in a certain portion of a watery extract of the contents of the 

 stomach the total amount of fixed chlorides (or muriates as 



