1881.] and Proteolytic Activity of Pancreatic Extracts. 157 



ascertaining how many cubic centimetres of milk can be changed to the 

 onset point of the metacasein reaction, in 5 minutes, by 1 cub. centim. 

 of the extract to be tested, at a given temperature. 



In settling the data on which the method is based, it was necessary, 

 as in the case of diastase, to determine the relations to tryptic action 

 of quantity, time, and temperature. 



Quantity and Time. — The rule of inverse relations between quantity 

 and time which was found to be valid within a wide range in the case 

 of diastase and starch, is only reliable in the case of trypsin and milk 

 within narrow limits. When the time of action exceeds 8 or 10 

 minutes the advent of the metacasein reaction is postponed beyond the 

 term indicated by the rule of inverse proportion, and this postpone- 

 ment increases as the time of action is lengthened. The following: 

 two sets of observations may be taken as samples of the results 

 obtained by experiment. 



Table VI. 



Showing the postponement of the metacasein reaction. 



The quantity of milk acted on in each experiment was 50 cub. 

 centims. diluted with water up to 100 cub. centims. The " calculated " 

 time in the third column was -obtained by taking the first observation 

 in each set as the standard of comparison. 



Quantity of pancreatic 

 extract added. 



Onset point of the metacasein reaction. 



Found. 



Calculated. 



Set I 



— Temperature 40° C. 



1 '0 cub. centim. 



3 minutes. 





0-8 



4 



3| minutes. 



6 



5 





0-4 



9 „ 





2 



30 



15 



Set II.— Temperature 16° C. 



4 - cub. centims. 



6 minutes. 





2-0 



16 „ 



12 minutes. 



i-o 



39 



24 



0-5 



105 



48 



25 



280 



96 



When the vanishing point of the metacasein reaction was taken as 

 the point of comparison, the results approximated more nearly to the 

 requirements of the rule of inverse proportion, especially at low tem- 

 peratures ; but still the evidence pointed in the same direction, and 

 indicated that trypsin, like diastase, exhausts itself in action at a pro- 



