374 Chittenden and Smith — Diastati'c Action of Saliva. 



Series XXIV. 



20 c.c. of filtered saliva were aeutralized, the proteids just satu- 

 rated with acid and the mixture diluted to 100 c.c. The solution 

 contained O'OOV per cent, combined HCl. 



10 c.c. of this diluted saliva were warmed with the specified per- 

 centages of acid for a definite time, then neutralizing and equalizing 

 mixtures were added and the diastatic action determined. 



Followino- are the results. 



Although the results are for some reason a little irregular it is very 

 evident that up to 0-005 per cent, of free acid there is, under these 

 conditions, no particular destruction of the ferment. With 0-010 

 per cent, on the other hand the destruction is very great. 



As to the bearing which these results have on the possible amylo- 

 lytic action of saliva in the stomach, it is plain that when the fluids 

 of the stomach acquire an acid reaction due to the presence of free 

 hydrochloric acid ptyalin will soon be destroyed. In the first stage 

 of digestion, however, when there is no free acid, the conversion of 

 starch into sugar can undoubtedly go on, and at this stage of the 

 process the proteid matter present may act as a shield to protect the 

 ptyalin and at the same time to stimulate it in its action, but as the 

 acid-proteids increase in amount and come nearer and nearer to 

 their saturation point it is possible that diastatic action may 

 entirely stop even before free acid makes its appearance. Certainly 

 all salivary ptyalin must ultimately be destroyed in the stomach. 



General conclusions. 



1. The diastatic action of saliva can be taken as a definite measure 

 of the amount of ferment present only when the dilution of the 

 saliva in the digestive mixture is as 1 : 50 or 100. The limit of 

 dilution at which decisive diastatic action will manifest itself with 

 formation oi reducing bodies is 1 : 2000-3000, under the conditions 

 previously given. 



2. The diastatic action of neutralized saliva is greater than that of 

 normally alkaline saliva. The difference is particularly noticeable 



