158 LA B OR A TOR Y G VIDE IN PH YSIOL OCY. 



After ten or fifteen minutes subject the mixture to a test 

 with Fehling's solution. If the conditions are normal a 

 copious precipitate of CuO indicates that a change has 

 been wrought in the mixture. The starch has been 

 changed to a reducing sugar by the ptyalin of the 

 salivary extract. 



(4) Mix equal volumes of starch paste and salivary 

 secretion in a beaker, place the mixture in the incu- 

 bator for ten or fifteen minutes; test with Fehling's 

 solution. The presence of a reducing sugar shows 

 that the secretion of the human salivary glands has 

 the power to change starch to sugar; to change an in- 

 soluble, indiffusible foodstuff to a soluble, diffusible 

 one. 



(5) Put a few crumbs of bread into a test tube; add 

 dilute iodine. Starch is an important constituent of 

 bread. 



(6) Put a few crumbs of bread into a beaker; add 

 salivary extract; place in the incubator twenty minutes. 

 Disintegration of the pieces and a marked increase of 

 the amount of reducing sugar indicates the digestive 

 action of saliva upon bread. 



(7) Put a bit of fibrin into salivary extract; place in 

 the incubator. An hour or a day will show no appar- 

 ent change in the fibrin. Had one used any other 

 proteid the result would have been the same. We are 

 justified in the conclusion that saliva contains no 

 ferment capable of changing proteids. 



(8) Put a bit of fat or a drop of oil into a few cubic cen- 

 timeters of salivary extract, shake vigorously; place in 

 incubator. After an hour or day one sees no change in 

 the fat or oil, and is justified in the conclusion that 

 saliva contains no ferment which acts upon fats. 



(9) To a small amount of raw starch add salivary ex- 



