354 Chittenden and Smith — Diastatic Action of S(diva. 



Destruction of salivary ptyalin hy sodium carbonate. 



To how great an extent is the retarding influence of sodium car- 

 bonate due to destruction of the ferment? Langley and Eves* state 

 that " sodium carbonate has a very slight destructive action on 

 ptyalin, its retarding power is out of all proportion to its power of 

 destrnction." 



The following experiments demonstrate the exact action of the 



sodium carbonate. 



Series X. 



70 c.c. of filtered saliva (the same saliva as used in Series IX), 

 were exactly neutralized witli 0*2 per cent. HCl and diluted to 

 140 c.c. 



The following mixtures were then prepared : 



Per cent. NaoCos, 0-05 0-15 0-30 0-50 



These were warmed at 40° C. for 30 minutes, then neutralized 

 with the amounts of dilute acid given below, water and starch 

 added, and the mixtures again warmed at 40° C. for 30 minutes. 



In the above digestive mixtures the ultimate dilution of the saliva 

 is the same as in series IX, 1 : 10, and being the same saliva, the 

 above results are directly comparable with those of series IX. 

 Warming saliva of the above strength with 0'05 and 0'15 per cent, 

 sodium carbonate for 30 minutes causes no destruction of the ptyalin 

 whatever, as the results of experiments 2 and 3 indicate, consequently 

 any diminished diastatic action in the presence of the above percen- 

 tages of alkaline carbonate must be due to a simple retardation of 



* .Joui-iial of l'hysiol()fi;y, vol. iv, No. 1. 



