308 JR. a. Chittenden — Papoid-digestion. 



anywhere near equal to the increase produced by the presence of 

 sodium bicarbonate. Hydrochloric acid much above 0*2 per cent, 

 inhibits almost entirely the proteolytic action of the ferment. 



Obviously, however, we cannot consistently argue from these 

 facts that any acid-reacting fluid will produce the same result as 

 hydrochloric acid, or that any alkaline-reacting fluid will give the 

 same marked increase in digestive action as sodium bicarbonate^ 

 These points are well illustrated by the following results, which at 

 the same time show the influence of several common substances 

 upon papoid digestion of various proteids. 



Influence of Sodium Carbonate on Papoid Digestion of Cooked 



Beef 



In this, as in the following series of experiments, unless otherw^ise 

 specified, each digestive mixture contained 0*5 gram papoid, JO 

 grams of the proteid designated (in this case cooked beef proteids, 

 prepared as previously described), and 25 c. c. of water containing 

 the indicated percentages of sodium carbonate, or other substances. 



The 10 grams of cooked beef contained 3*7767 grams of dry 

 proteid (110° C). 



The digestions were warmed at 45° C. for 5^ hours. 



Sodium carbonate. 



Weight of 

 undigested residue. 



Proteid digested. 



(Neutral) 



1-8424 



grams 



51-2 



per cent, 



0'25 per cent. 



1-7697 





53-1 





0-50 " 



1-7906 





52-5 





1-00 " 



1-8934 





49-8 





2-00 " 



1-8541 





50-9 





4-00 " 



2-1562 





42-9 





Without papoid. 











2*00 per cent. 



3-4607 



<( 



8-3 



( ( 



These results show that the presence of sodium carbonate in small 

 quantity tends to increase slightly the digestive action of papoid. 

 Aside from this slight increase, the activity of the ferment is not 

 noticeably affected by the alkaline salt until it is present in quanti- 

 ties above 2 per cent., and even then the inhibition is compara- 

 tively slight. This seems the more remarkable when it is remem- 

 bered that sodium carbonate is a fairly strong alkaline salt, and 

 doubtless on that very account fails to produce the marked increase 

 in digestive action produced by the weaker bicarbonate. In any 

 event, it is evident, from the experiment, that papoid will not be 



