Chittenden and Smith — Diastatic Action of' /Saliva. 269 



It is thus manifest from our results that the retarding influence of 

 the larger perceutages of acid-peptones is out of all proportion to 

 their power of destruction. Still larger percentages of acid-saturated 

 peptones produce a much gi'eater destruction. Thus, by warming 

 10 c.c. of a neutral dilute saliva (1 : 5) with a solution of peptone 

 saturated with acid, in such proportion that the mixture contained 

 0*430 per cent, combined HCl, there was in 30 minutes an almost 

 complete destruction of the ferment. 



b. Influence of free acid. 

 In view of the fact that some time ago one of us* was of the 

 opinion that small percentages of acidf tended to increase the diae- 

 tatic action of saliva, it was of especial interest now to ascertain defi- 

 nitely whether free acid when present in small percentages does inva- 

 riably retard diastatic action. Langley and Eves state that " although 

 saliva neutralized to litmus sometimes shows an increase of action on 

 the addition of 0-0005 to 0*001 per cent. HCl ; yet if the proteids of 

 the saliva be saturated with acid, there is a diminution of its amylo- 

 lytic action, although no free acid is present in the saliva." This we 

 cannot regard as correct without qualification, since our experiments 

 appear to show that saliva with its pi'oteid matter saturated with 

 acid has a greater diastatic action in a given time than saliva simply 

 neutralized, provided the percentage of acid-saturated proteids is not 

 too large. The same investigators further state "that 0*0015 per 

 cent. HCl distinctly diminishes the amylolytic action of pytalin," 

 and "since 0*0015 per cent. HCl increases amylolytic action it seems 

 very unlikely that 0*005 per cent, should increase it ;" but as Lang- 

 ley and Eves, in studying the influence of free acid, apparently used 

 diluted, neutralized saliva, in which the proteids present were not 

 combined with acid, depending simply upon dilution to avoid the 

 influence of these bodies, it seems to us a little uncertain whether 

 their results are strictly accurate on this point, since saliva even 

 very much diluted does contain some proteid matter. They, how- 

 ever, state in this connection that " we have often found that solu- 

 tions which we have thought carefully neutralized have been in- 

 creased in action by the presence of still smaller percentages of 

 acid, viz : 0*0005 to 0*0010 per cent." Here, however, so far as theij 

 results show, the observed increase of activity may have been due 



* Chittenden and Griswold, loc. cit. 



f Considered as 0-005 per cent., although we now know the above figure could not 

 represent free acid, owing to the proteid matter of the saliva. 



