Chittenden cuid Smith — Diastatic Action of Saliva. 353 



These figures lead to the following percentages of starch converted 

 Into sugar under the different degrees of alkalinity. 



By comparing the two preceding columns of diffei'ences it is very 

 manifest that the alkaline carbonate has a much greater retarding 

 action on the more dilute saliva than on the stronger solution ; very 

 noticeably so in the mixtures containing 0-025 and 0*050 per cent, of 

 the alkaline salt. 



By diluting neutralized saliva still more, and then using quantities 

 of the fluid equal to 2 c.c. of the original saliva, making in the 100 c.c. 

 of digestive mixture a dilution of 1 : ')0, even 0'005 per cent, of sodium 

 carbonate is sufficient to retard the diastatic action of the ferment 

 almost completely ; thus, in one experiment with the above amount 

 of saliva in the presence of 0*005 per cent, sodium carbonate but 

 4-03 per cent, of the starch was converted into sugar in 30 minutes 

 at 40° C, while the same amount of saliva alone converted 27*08 per 

 cent, of the starch into sugar. By increasing the percentage of 

 alkaline cai'bonate the diastatic action was stopped completely. 



It is thus evident that the percentage of alkaline carbonate which 

 absolutely or to a certain extent hinders the diastatic action of saliva 

 can be designated only for a definite mixtui-e, and not in a general 

 sense. Langley and Eves* state that sodium carbonate of O'OOIS 

 per cent, causes a retardation in the action of ptyalin ; our experi- 

 ments with unneuti-alized saliva diluted, plainly show that even much 

 smaller percentages of alkalinity may decidedly retard the action of 

 the ferment, wiiile in similarly diluted saliva 0*005 percent, of sodium 

 carbonate may prevent diastatic action almost entirely. 



Again Langley and Evesf state that the "amylolytic action of saliva 

 becomes less the more alkaline salt there is in the solution, the rate of 

 decrease is, however, slow compared with that which occurs when 

 hydrochloric acid is added in similarly increasing quantities." 

 The rate of decrease, however, as our experiments plainly show, is 

 dependent greatly upon the amount of dilution. 



* Journal of Physiology, vol. iv, Xo. 1. f Ibid. 



