GASTRIC JUICE AND CHANGES IN STOMACH. 153 



the first step in the gastric digestion, although some authors 

 claim to have recognized the albumose stage as the primary 

 one in some cases. While this acid reaction may take place 

 in pure aqueous-acid solution, it is much more quickly reached 

 in presence of pepsin, as is the case in the stomach. Experi- 

 ments with artificial mixtures show that the combination then 

 is almost immediate, as is made evident by the loss of " free " 

 acidity, to be explained below. Then the hydrolysis goes on 

 and the various derived products mentioned in a former chap- 

 ter are produced. In the gastric digestion it is likely that the 

 cleavage does not usually extend beyond the production of 

 the secondary albumoses; that is, not much real peptone is 

 formed in the time naturally consumed in normal digestion. 

 In practice the larger part of the peptone production is doubt- 

 less left for the trypsin conversion. 



Hydrolytic cleavage beyond the acid albumin stage is 

 favored by abundance of free acid, but in absence of this it 

 still goes on. In actual digestion the whole of the hydro- 

 chloric acid may be combined with albumin, leaving some of 

 the latter in excess even, yet primary and secondary albumoses 

 will appear leaving the remaining native albumin to begin the 

 reaction later. In other words, it is not necessary that one 

 stage of the digestive process must be complete before the 

 following may begin. All these reactions may be in progress 

 simultaneously, and if needed hydrochloric acid will be taken 

 from the advanced products to hasten the beginning hydrolysis 

 of the protein yet to be digested. It has in fact been shown 

 that hydrochloric acid in combination with leucine and other 

 amino acids, which it will be recalled are advanced products of 

 proteolysis, will still digest fresh albumin rather rapidly, but 

 not as well, of course, as the equivalent amount of free acid. 



The amount of acid taken up by an original native protein 

 substance during gastric digestion has been referred to al- 

 ready. Starting with a given weight of pure protein hydro- 

 chloric acid may be added until a distinct reaction is shown by 

 dimethylaminoazobenzene. This indicator behaves as a very 



