364 Chittenden and iS/jiith — Dlastatic Action of Saliva. 



In this series of experiments where the percentage of combined 

 acid in the digestive mixture is much greater than before, tlie same 

 increase in diastatic action is noticed. With the largest quantity of 

 saliva however where the amount of combined acid is 0-006 per cent, 

 we seem to have reached a point where the acid-proteid matter ceases 

 to stimulate and begins to retard the action of the ferment. That 

 this is actually the case we have proved by another experiment con- 

 firmatory of the preceding one, using in the digestion however two 

 grams of starch instead of one. 



Thus while an amount of neutral saliva, equal to 20 c.c. of the 

 original secretion converted 39'08 per cent, starch into sugar, the 

 same amount of saliva having all of] its proteid matter combined Avith 

 acid converted under the same conditions 38*21 per cent, "of the 

 starch, a decrease of 0*87 per cent; in this case however the amount 

 of combined acid present in the 100 c.c. of digestive mixture was 0-008 

 per cent. 



It thus seems plainly proven that up to a certain percentage the 

 presence of acid-proteid matter in the saliva tends to decidedly stim- 

 ulate its diastatic action. We cannot therefore agree with Langley 

 and Eves that ptyalin a';ts best in evei-y instance in a neutral solution, 

 for our results certainly show an increased action of the ferment in 

 the presence of the acid-proteids, except where the latter are present 

 in comparatively large amount. 



The only possible fallacies which suggest themselves here are 

 traces of undetectable alkali in the starch and the presence of phos- 

 phates of calcium or magnesium. This result moreover makes clear 

 many statements previously recorded which would otherwise be diffi- 

 cult of explanation. Thus it has been recorded by Astaschewsky,* 

 that the saliva of the parotid gland possesses a very faint acid reac- 



* Centralbl. med. AViss., 1875, 15. 



