COMPOSITION OF HUMAN MIXED SALIVA. 263 



after breakfast fail to show any close parallelism between the 

 variations in amylolytic power and variations in alkalinity. 

 Thus, the most marked differences in digestive power are fre- 

 quently seen with salivas which show only a slight difference 

 in alkalinity, and on the other hand marked differences in 

 alkalinity may be associated with minor differences in amylo- 

 lytic power. 



III. ALKALINITY, AMYLOLYTIC POWER AND COMPOSITION 

 OF HUMAN SALIVA BEFORE AND AFTER EATNG. 



In view of the preceding results, the following set of 

 experiments Was tried, in which, in addition to alkalinity and 

 amylolytic power, the proportion of dry solids and inorganic 

 salts of the saliva was likewise determined. The dry solids 

 were determined by simply drying a weighed amount of the 

 filtered saliva usually 5 grams on a water-bath and 

 heating at 105 C. in an air-bath until of constant weight. 

 The inorganic salts were then determined by careful ignition 

 of the residue. In some of the following experiments relative 

 amylolytic action was determined by Robert's * method, the 

 method being based on the different lengths of time which 

 solutions of different amylolytic power require to digest a 

 certain amount of starch paste to the achromic point. The 

 results obtained by this method are expressed in minutes ; 

 i. e., the number of minutes which elapse from the time the 

 diluted saliva is added to the starch paste until the appearance 

 of the achromic point. 



The results obtained are shown in the table on p. 264. 



In these results we have a suggestion of the same general 

 tendency toward decrease of amylolytic power and lowered 

 content of alkaline salts in the saliva secreted after the morn- 

 ing meal, while as accompanying results we see corresponding 

 fluctuations (although not in all cases) in the proportion of 

 total solids, organic matter, and inorganic salts, thus bearing 

 out the view that the variations in amylolytic power are 

 connected mainly with changes in the general concentration 



* See Gamgee's Physiological Chemistry of the Animal Body, ii, p. 66. 



