366 (Jhittetiden and ^mith — Diastatic Action of Saliva. 



digestion still further by experimenting likewise with peptones, and 

 in studying the influence of acid-peptones on the action of the fer- 

 ment we have been impi'essed with the striking effect of very minute 

 quantities of acid on the ordinary action of peptones, increasing it 

 very decidedly. It has already been shown that the presence of 

 0-05, O'l and 0*2 per cent, of neutral peptone produces, in neutral 

 solutions, a like increased diastatic action ; with 0*5 per cent, peptone 

 the increase is as much as with 0*2 per cent. ; that is, in the case of 

 saliva considerably diluted. With acid-peptones, however, the effect 

 produced is quite different, and the amount of combined acid neces- 

 sary to produce this different effect is quite small. 



Peptones as usually prepared contain a small amount of combined 

 acid. The sample we used required per gram 0*014 gram Na^Co, to 

 make it neutral; this would be equivalent to 0*00964 gram HCl. 

 Consequently the percentage of combined acid in the peptone, 

 assuming it to be hydrochloric acid, would be 0*964 per cent. With 

 such an acid-peptone the following experiments were tried. 



Series XVII. 

 20 c.c. saliva were neutralized and diluted to 100 c.c. ; of this solu- 

 tion 10 c.c, equal to 2 c.c. of original saliva Avere used in each 

 digestion. Four experiments were tried, in three of which 0-050 

 gram, 0*100 gram and 0*200 gram of the above acid-peptone were 

 added. Following are the results, after warming the mixtures at 40° 

 C. for 30 minutes. 



Comparing these results with those obtained by similar percent- 

 ages of neutral i)eptoue the difference is sufficiently striking, and yet 

 the pei'centage of combined acid in the digestive mixture, where 

 there is present 0*20 gram of acid-peptone, is but 0*0019 per cent, 

 calculated as HCl. 



Experimenting with ))eptones completely saturated with acid, and 

 in this case with what was known to be hydrochloric acid, results 

 similar to the above were obtained, with, however, several suggestive 

 deviations. The following series of experiments will serve to illus- 

 trate the main ))oints of interest. 



