356 Chittenden and Smith — Diastatic Actio?i of Saliva. 



cent, more starch was converted into sugar during 45 minutes at 40° 

 C. ; this with 25 c.c. of saliva in 100 c.c. of the digestive mixture. 

 This effect we attributed to a direct stimulating action on the part 

 of the proteid matter. Langley and Eves,* however, object to this 

 conclusion, although they bring forward no facts to prove the con- 

 trary. Considering that litmus will not detect less than O'OOi per 

 cent, acid or alkali they state that there may be in the neutralized 

 fluid an excess of acid or alkali to this extent, and if, as may well be 

 the case, ptyalin acts best in a neutral solution, the effect of the pep- 

 tone might be due to its putting hors de combat the slight excess of 

 acid or alkali which remains on apparent neutralization. But as 

 Langley himself has shown, the proteid matter naturally present in 

 25 c.c. saliva, or even much less, is far more than sufficient to combine 

 with and render inert any such amount of free acid or alkali. We 

 see no other possible explanation of the action of peptones on the 

 diastatic action of saliva in a neutral solution than a direct stimula- 

 tion of the ferment. Moreover, Langley and Eves have found that 

 when neutralized saliva is diluted a hundred times, peptone is still 

 able to increase the rate at which it converts starch into sugar, from 

 which they are forced to conclude that the small amount of acid or 

 alkali which may be present, cannot exert, in such a dilution, any 

 retarding influence. We present the following ^ additional results 

 confirmatory of our previous experiments. 



In our present experiments we have, however, used much less 

 saliva, and also smaller percentages of peptone. 



Series XL 



20 c.c. of filtered saliva were neutralized and then diluted to 100 c.c. 



0*8 gram of pure albumin-peptone was dissolved in water, made 

 exactly neutral with Na^Co^ and the solution diluted to 100 c.c. 



10 c.c. of the diluted saliva were employed in each digestion, and 

 of the peptone solution quantities equivalent to 0*05, O'l, and 0*2 

 gram of peptone. Length of digestion, 30 minutes. 



Here, with tlie smaller amount of ferment, tl)e increase is not so 

 great as with tlic larger quantity of saliva and with the longer 



I Journal of Ph3'siology, vol. iv. No. 1. 



