240 DIGESTION. 



was generally supposed to be the free acid of the gastric juice. It is chiefly on the last- 

 named observations which have been supported by Bernard in his later publications and 

 by the confirmatory experiments of Lehmann and others that those who admit the 

 presence of free lactic acid in quantity in the gastric juice rest their belief. 



We have already referred to the experiments of Bernard, which show that an artificial 

 fluid containing chloride of sodium and lactic acid in solution behaves, during distillation, 

 in every way like the normal gastric juice. These show, also, how hydrochloric acid 

 may be produced during the last period of the distillation by decomposition of the 

 chlorides. We have seen that this observation was confirmed by Lehmann, who noted 

 the same reaction during evaporation at the ordinary temperature, in vacuo, although he 

 supposed the action in the gastric juice to be upon the chloride of calcium instead of the 

 chloride of sodium. Lehmann found in the acid residue, free lactic acid, lactate of lime, 

 and alkaline chlorides. Bernard and Lehmann have brought forward other experimental 

 facts to show that the gastric juice contains lactic acid. If starch be boiled in a solution 

 containing hydrochloric acid, it soon loses its property of forming a blue compound with 

 iodine ; while if it be boiled with lactic acid, no such change is observed. If starch be 

 boiled with a solution containing hydrochloric acid, to which has been added a soluble 

 lactate in excess, it remains unaltered ; which shows, according to Bernard, that hydro- 

 chloric acid in a free state cannot exist in the presence of an excess of a salt of lactic 

 acid. By similar experiments, the same observer assumes to prove that the existence of 

 hydrochloric acid is inadmissible in the presence of a phosphate or an acetate in excess. 

 Lehmann has found that starch boiled with gastric juice retains the property of being 

 colored blue by iodine. These experiments are considered by Bernard as positive proof 

 that the acid of the gastric juice is the lactic; and the fact "seems to him to be at the 

 present day beyond contestation." The facts adduced by Lehmann, however, are even 

 stronger. By operating upon a large quantity of gastric juice, he formed the lactates in 

 such a quantity that he was enabled to subject them to ultimate analysis and determine 

 positively the nature of the acid. He found that the acid had the composition of lactic 

 acid formed from sugar, and not that of the acid formed from the juice of the muscular 

 tissue. 



In view of the facts above mentioned and the somewhat uncertain basis on which 

 the supposition of the presence of free hydrochloric acid is founded, it seems almost cer- 

 tain that the principal free acid of the gastric juice is the lactic. It is important to re- 

 member that, while the experiments of Bernard and Lehmann were made on gastric 

 juice from the dog, they have been confirmed, in their essential particulars, by the more 

 recent observations of Prof. F. G. Smith on the normal gastric juice from the human 

 subject. 



It now only remains to discuss the question of the existence in the gastric juice of the 

 acid phosphate of lime, to the exclusion altogether of free acids ; a theory first proposed 

 by Blondlot in 1843, and entertained and defended by him, as late as 1858, notwithstand- 

 ing the fact that this view ha's met with no favor among physiologists. 



To Blondlot belongs the rare merit of having been one of the first, if not the very 

 first, to propose and execute an experiment by which the normal gastric juice could be 

 obtained in quantity from a living animal. In his first analysis of the fluid thus obtained, 

 he denied the existence of any acid principles except the biphosphate of lime. This 

 view he holds at the present day ; and, notwithstanding the elaborate researches of the 

 most distinguished physiological chemists, in all of which a free acid of some kind has 

 been recognized, he still ardently defends his original position. The question of the exist- 

 ence in the gastric juice of the acid phosphate of lime, to the exclusion of free acids, may 

 be discussed in a few words. 



Assuming that the gastric juice contains a free acid, a view which the arguments of 

 Blondlot fail to disprove, the question arises whether the biphosphate of lime may not 

 also exist in this fluid. On this point there can be no doubt. All the modern analyses 



