156 THE MICHIGAN ACADEMY OF SCIENCE. 



filtered through ordinary filter paper (S. & S. 'So. 595) to remove mucin 

 and suspended particles, and diluted to 200 c.c. with distilled water. 

 This solution was then subjected to filtration in the following manner: 



In each of two funnels were placed two folded filter papers 

 (Schleicher and Schiill hardened filters No. 575), and the funnels so 

 arranged one above the other on a ring stand that the stem of the upper 

 funnel touched the side of the filter paper in the lower one, and the 

 stem of the lower one passed into an Erlenmeyer flask. The saliva was 

 thus passed through four thicknesses of paper. This first filtrate was 

 designated as "2 X 2." This then was passed through a second set of 

 filters, similarly arranged, giving filtrate "4 X 2," then through another 

 set producing ''Q X 2," and finally through a, fourth set producing filtrate 

 *'8 X 2," thereby causing the liquid to pas& through eight double filter 

 papers. The filtration was carried on under 'a black cloth, protecting 

 the enzyme against the action of light. Five c.c. of the 10 per cent, 

 saliva had been set aside at the same conditions of light and tempera- 

 ture as the filtering liquid for control. 



Each successive filtrate was tested by adding 0.5 c.c. of it to 30 c.c. 

 of a 1 per cent, starch solution containing glycerin at 34°. Portions 

 of this mixture were removed from time to time to note the progress 

 of digestion, if any. This was done by adding to 2 c.c. a few drops 

 of iodine solution and noting the color reaction. The pipette employed 

 in withdrawing the digesting liquid was rinsed after each use with boil- 

 ing distilled water. At the same time that each filtrate was tested, a 

 corresponding quantity of the control was similarly tested. The time 

 necessary for each fiftrate and control to produce achromicity of the 

 starch solution was noted. 



The table gives result of one such experiment : 



Duration of filtration — 2 hours and 30 minutes. 



A large number of similar experiments produced the same ■ results, 

 indicating beyond a doubt the removal of ptyaliu from its solution by 

 hardened filter paper. Inasmuch as the action of ptyalin is not directly 

 proportional to the quantity present in concentrated solutions, it is 

 necessary to work with diluted saliva and to test with small quantities 

 of this, "less the effect of the removal of a small quantity of ptyalin 

 be masked by the activity of the unretained portion. 



The question now arises as to what this removal is due. Three an- 

 swers present themselves: (1) The molecule of ptyalin, as in the case 

 of a precipitate, may be mechanically retained on the filter; or (2), 

 aeration may have had a destructive*^ effect, or (3), the ptyalin may 

 have entered' into firm combination with the material of the filter paper, 

 i. e., it may have been fiaced. To determine whether the paper acted by 

 mechanical retention, a 10 per cent, solution of saliva was filtered 

 through a Berkefeld filter. A portion of the saliva was previously set 



