ON PANCREATIC PROTEOLYSIS. 221 



percentage of either free or combined acid, really present. 

 The question is one of considerable physiological importance, 

 and if it is true that the pancreatic juice acting in an acid 

 solution will do more work than in a neutral solution, it 

 should be clearly established. We have, therefore, first turned 

 our attention to this point. 



Experiment 44. With neutral extracts of ox pancreas and pig's pancreas 

 (neutral to litmus). 



10 c.c. of the extract of pig's pancreas required 4.95 c.c. 0.2 per cent HC1 

 to combine with all the proteid matter present.* 



10 c.c. of the extract of ox pancreas required 2.55 c.c 0.2 per cent HC1 

 to combine with the proteids. 



In the digestions with pig's pancreatic fluid each mixture contained 

 10 c.c. of the extract, while with the pancreatic fluid from the ox pancreas 

 30 c.c. of extract were used in each case. Acid was then added to the 

 mixtures as specified, the percentages being calculated on the total 

 volume (50 c.c.) of the digestive mixtures. In no case was any free acid 

 present. 



Ox Pancreatic Juice. 1 JJ a . 



Neutral .......... 0.3279 gram 67.21 per cent 100.0 



Proteids combined with HC1 



Quarter saturated (0.007% HC1) 0.3782 62.18 92.5 



Half " (0.015% HC1) 0.4995 50.05 74.4 



Wholly " (0.030% HC1) 0.8710 12.90 19.1 



Pig's Pancreatic Juice. 



Neutral ........... 0.0435 95.65 100.0 



Proteids combined with HC1 



One-sixth saturated (0.0016 % HC1) 0.0469 95.31 99.6 



Quarter " (0.0025% HC1) 0.0550 94.50 98.7 



Half " (0.0049% HC1) 0.0826 91.74 95.9 



Wholly " (0.0099% HC1) 0.2239 77.61 81.1 



Experiment 45. 10 c.c. of the extract of ox pancreas required 4.3 c.c. 0.2 

 per cent HC1 to combine with the proteids. 



10 c.c. of the extract of pig's pancreas required 4.6 c.c. 0.2 per cent HC1 

 to combine with the proteids. 



In the digestions, 10 c.c. of the extract of pig's pancreas and 30 c.c. of 

 the extract of ox pancreas were employed. 



* Tropaeolin oo in methyl alcohol was used as the indicator for free acid. 

 Obviously, in conducting the titrations, deduction was made for the excess of 

 acid required to bring out the color. 



