NaOH 

 12 



u 

 u 



a, 



o 



o 



6 



10 



8 



6 











Days 



3 

 at 38' 



Fig. 4. Action of pepsin on gelatin partially hydrolyzed by acid. 500 cc. of 

 5 per cent gelatin containing 12 cc. of 4.0 M HCl (pH 1.8) kept at 38°. pH kept 

 constant by addition of more HCl from tirnc to time. 50 cc. samples pipetted 

 out at intervals of 2 days and kept at 3° until all had been taken. 5 cc. of 5 per 

 cent pepsin then added and the samples replaced at 38°. Formol titration was 

 run on 5 or 10 cc. The values plotted have been calculated on the basis of 10 

 cc. of 5 per cent gelatin. 



TABLE III. 



Addition of Pepsin to Gelatin Partially Uydrolyzed by Acid. 



Before addition of pepsin . 

 Increase due to pepsin . . . 



Formol Titration per 10 cc. of Solution. 



1.9 

 2.1 



3.3 

 (1.2) 



4.0 

 2.0 



6.4 

 2.0 



8.0 

 1.0 



11.4 

 0.0 



12.6 

 0.0 



65 



