3Y2 Chittenden and Smith — Dimtatic Action of Saliva. 



Here a slight increase is noticed with 0-0006 per cent, followed at 

 0-002 per cent, by a rapid fall in diastatic action. 



With stronger solutions of ptyalin, like results were obtained as 



follows : 



Series XXIII. 



Filtered saliva was neutralized and the proteids just saturated 

 with HCl. An amount of this fluid equivalent to 5 c.c. of the orig- 

 inal saliva was used in each digestion. In this amount there was 

 present 0-00266 gram combined HCl, but no free acid whatever. 



Following are the results of digestions with this saliva in the 

 presence of the percentages of free acid specified. 



Wt. Cu in Total amt. 



Per cent, free add. one-eighth. sugar. Starch converted. 



0-0956 gram. 0-3896 gram. 3.5-07 per cent. 



0-0005 0-0966 03936 35-43 



0-0010 0-0867 0-3536 31-80 



0-0020 0-0162 00728 655 



00030 trace 



Increasing now the amount of saliva still further, so that the per- 

 centage of combined acid reaches a point where its retarding influence 

 begins to be felt, the presence of the smallest amount of free acid then 

 causes at once a decided decrease in diastatic action. Thus, using the 

 same saliva as was employed in the preceding series, only in such 

 quantity that 20 c.c. of original saliva were present in each diges- 

 tive mixture, it was found that the free acid produced a much greater 

 retarding effect than before. The percentage of combined hydro- 

 chloric acid, in the form of acid-proteids, contained in each digestive 

 mixture was 0-01064 per cent. Following are the results of the 

 diastatic action. 



This result accords with the statement made by Langley and 

 Eves, "that if the proteids of saliva be saturated with acid there is a 

 diminution of its amylolytic action, although no free acid is present 

 in the saliva. This diminution is made more marked by the addition 

 of the smallest quantity of hydrochloric acid." The above quanti- 

 tative results plainly testify to the accuracy of the latter part of 

 their statement. As to the action of the acid-saturated proteids that 

 is wholly dependent upon the percentage present. 



