Chittenden and Smith — Diastatic Action of Saliva. 361 



standard solution of hydrochloric acid of known strength,* we have 

 found that 0-003 per cent, of this acid can be detected with cer- 

 tainty, a drop of such a mixture giving a distinctly recognizable 

 violet color. A smaller percentage cannot be recognized and we 

 have therefore invariably deducted the above amount in our various 

 tests for free acid. 



The amount of proteid matter naturally present in saliva and 

 which is capable of combining with acids, is apparently quite con- 

 stant. Langley and Eves found as a mean of several observations 

 that 5 c.c. of filtered, neutralized saliva contained proteids capable of 

 combining with 2 c.c. of 0-1 percent, hydrochloric acid. We have 

 found as a mean of eight determinations that 20 c.c. of filtered, neu- 

 tralized saliva contained proteids capable of combining with 7*74 c.c. 

 0*1 per cent, hydrochloric acid. In an attempt to ascertain approxi- 

 mately how much proteid matter this amount of acid signified, we 

 took the results of our experiments with peptones, in which we found 

 that 1 gram of pure neutral peptone required 48*0 c.c. 0*1 per cent, 

 hydrochloric acid to saturate it. Consequently 1 c.c. of 0"1 per cent, 

 acid would combine with 0*0208 gram peptone, and assuming that the 

 combining power of the proteids present in saliva is the same as that 

 of peptones, the 20 c.c. of saliva would contain 0"16099 gram proteid 

 matter, equal to 0'804 per cent.; a result which at once shows that 

 the combining power of the proteids of saliva and peptone must be 

 quite different, or as is more probable, that considerable of the acid 

 added, is used up in reacting with the phosphates of the alkalies 

 present in the saliva. 



Saliva, as a rule, does not contain much more than O'o per cent, 

 solid matter, and Hammerbacher has found in human mixed saliva 

 0*139 per cent, albumin and ptyalin.f 



A comparison of the diastatic action of neutral saliva considerably 

 diluted, and similarly diluted saliva in which the proteids present 

 have been saturated witls acid, shows at once that acid-proteid 

 matter, even though present in but small quantity, has a distinctly 

 stimulating action on the salivary ferment. 



The following experiments will illustrate this point and also show 

 the extent of the stimulation. 



Series XIV. 

 A. 40 c.c. filtered saliva were neutralized and then diluted to 

 200 c.c. 



* Ail of our standard acid soiulions were of exactly tlie strengtli specified, as was 

 proved by titration with standard solution of silver nitrate, 

 f Jahresbericht fiir Thierclieinie, 1881, 269. 



