Chittenden and Painter—Action of Saliva. 61 
over, only neutral bodies could be experimented with, since the 
smallest quantity of either free acid or alkali would exert its own 
peculiar destructive action on the ferment.* In view of this fact also, 
we have invariably used chemically pure salts and those frequently 
recrystallized to be sure of the absence of deleterious impurities. 
Method employed. 
A few preliminary experiments clearly indicated that the presence 
of very small percentages of foreign substances exercise a decided: 
effect, on the amylolytic action of saliva, and thus the investigation 
resolved itself into a study, not of the percentages requisite to com- 
pletely hinder the power of the ferment, under given conditions, but 
of the relative action of small percentages on the amylolytic power 
of the ferment. This seemed to us the more important, since we soon 
found that substances which, present in comparatively large amount 
tended to hinder amylolytic action, would when present in small 
quantities actually increase the activity of the ferment. Hence, we 
deemed it best to use accurate quantitative methods for determina- 
tion of amylolytic action; such as would indicate small variations 
with certainty. 
The experiments were made in series, in which one digestion of 
each series served as a control for comparison. The volume of each 
digestive mixture was 100 ¢. ¢., in which was present 1 gram of per- 
fectly neutral potato starch, previously boiled with a portion of the 
water, 10 ¢. c. of a diluted neutral salivat and a given quantity of the 
substance to be experimented with. The mixtures were warmed at 
40° C. for 30 minutes, after which further action of the ferment was 
stopped by heating the solution to boiling. The extent of amylo- 
lytic action was then ascertained by determining in one-fourth of the 
solution, the amount of reducing substances by Allihn’s{ gravimetric 
method. From the amount of reduced copper thus obtained, the 
total amount of reducing bodies was calculated (as dextrose), from 
which in turn was calculated the percentage of starch converted. 
* Chittenden and Smith, Transactions Conn. Acad. Arts and Sciences, vol. vi, p. 
343. x 
+ The saliva was human, mixed saliva, freshly collected. It was prepared for use 
by being filtered, made exactly neutral, then diluted in the proportion of 1;5, Thus 
in each digestion there were present 2 c. ec. of undiluted saliva. 
} Zeitschrift fiir Analytische Chemie, Jahrgang xxii, p, 448, 
