GASTRIC JUICE AND CHANGES IN STOMACH. I/ 1 



digestion it will appear that some of them are identical with 

 those formed in the stomach or by pepsin-hydrochloric acid 

 action in general. Others appear at first sight quite distinct 

 and their existence leads to the long-accepted notion that the 

 peptic action is incapable of carrying the conversion of proteins 

 through to the final stages. The conclusions which may be 

 drawn from the most recent of the long investigations which 

 have been carried out on this question are somewhat conflict- 

 ing, but in the main they show that with a sufficiently long 

 time allowed the end products of peptic and tryptic digestion 

 are essentially the same. 



Some idea of the extent of the changes taking place in 

 reasonably prolonged peptic digestion may be obtained from 

 a study of the rapidity of combination with hydrochloric acid 

 which has been already referred to in speaking of digestion 

 experiments. A digestive mixture was made with 90 gm. of 

 coagulated and finely divided white of egg, 900 cc. of approxi- 

 mately 0.2 per cent hydrochloric acid and 150 mg. of com- 

 mercial pepsin. Two portions of this mixture, of 25 cc. each, 

 were titrated at once, one with use of phenol-phthalein and 

 the other with dimethylaminoazobenzene. The remainder of 

 the mixture was poured into a large flask which was main- 

 tained at a temperature of 40 in a thermostat through a 

 number of days. Titrations were made from time to time 

 with the following results, 25 cc. of the mixture being always 

 taken. The phenol-phthalein titration was made warm, the 

 other cold. 



Time. 



at once 

 10 hours 

 24 " 

 40 " 

 96 " 

 168 " 



It appears, therefore, that the " total " acidity as measured 

 in the phenol-phthalein titration undergoes a slight increase. 

 The hydrochloric acid remains, and added to it are some diges- 

 tive products of pseudo-acid character, but strong enough to 



