Chittenden and Smith — Diastatic Action of Saliva. 347 



the usual way, and the results are expressed in percentage of starch 

 converted into suo-ar. 



The degree of dilution to be employed depends, of course, upon 

 the amount of ferment present. We have usually diluted the saliva 

 5 or 10 times, and then added an amount of the diluted fluid cor- 

 responding to 0-5-2-0 c.c. of saliva, which in the 100 c.c. of digestive 

 mixture makes a dilution of from 50 to 200. As we shall have 

 occasion to state later on, neutralized saliva needs even a greater 

 dilution. The method certainly appears as advantageous as that pro- 

 posed by Dr. Robertsf a few years ago, and has the advantage of 

 giving gravimetric results, instead of being dependent upon the dis- 

 appearance of a shade of color. In using the method with different 

 solutions it will always be found necessary to exactly neutralize the 

 ptyalin-containing solutions, before diluting them, since variations of 

 alkalinity, even though infinitesimal in amount, may produce dis- 

 cordant results. Moreover, it is better to warm the ptyalin solution 

 with the starch for not longer than 30 minutes. 



The amount of dilution which saliva will endure and still show 

 diastatic action depends naturally upon the amount of ptyalin 

 present in the secretion and also upon the reaction of the fluid, 

 whether it be alkaline or neutral. The following series of experi- 

 ments show the average of our results on this point. 



Series IV. 



Normally alkaline saliva, 1 per cent, starch. 



Wt. Cu in Total amount Starch converted 



one-eighth. of sugar. into sugar. 



1 C.C. saliva, 0-0152 gram. 0-0704 gram. 6-33 per cent. 



I 0-0057 0-0272 2-44 



i 0-0037 0-0176 1-59 



\" . y less than 1 per cent, of starch converted. 



./^i\ trace ) 



It is thus seen that when the dilution is as 1 : 250, an appreciable 



* Neutralized saliva. 



f William Roberts : Jahresbericht fiir Theirchemie, 1881, 290. 

 X To ensure greater accuracy the saliva was diluted ten times and amounts of the 

 diluted fluid added corresponding to the above. 



