SOME PHYSICAL PROPERTIES OF PTYALIN. 157 



aside as control. 195 c.c. were filtered at a pressure of 29 inches in 

 seven minutes. The filtrate was found to be identical in activity with 

 the unfiltered solution. Evidently, the cause is not mechanical reten- 

 tion, as the pores of the Eerkefeld filter are known to be smaller than 

 those of the filter paper. 



To determine the effect of aeration, an upright tube of amber glass, 

 18 inches long, and provided at the bottom with a capillary tip, was 

 filled to a depth of about 15 inches with glass beads, and a 10 per cent, 

 saliva was poured in. The upper part of the tube was connected with 

 a suction pump, and a vigorous aeration of the contents of the tube was 

 maintained for 24 hours. At the same time a portion of the saliva was 

 set aside for control. Portions of the aerating saliva were drained off 

 from the tube at the end of 3, 6, 9 and 24 hours, and tested as previously 

 described for diastatic activity, and compared with the activity of the 

 corresponding control. Even at the end of 24 hours' aeration, the aerated 

 saliva was identical in activity with the unaerated control. Therefore, 

 aeration has not produced the effect observed on filtering the saliva. 



Szumowski (1898) demonstrated the fixation of enzymes (ptyalin, 

 rennin, pejjsin and trypsin) by fibrin. Effrout states that enzymes are 

 fixed by different substances, such as silk and fibrin. Chevreul (1853) 

 tested the fixing action of linen, cotton and silk on such substances as 

 NaCl, Hg'Clo, H0SO4 and others. One experiment, for instance, showed 

 that cotton absorbs HgCL and water in proportion to the solution, and 

 moreover retains a portion of the HgCL with so much force that, after 

 having been washed until the wash water no longer precipitates AgNOs, it 

 (the cotton) is colored by HoS solution, and acts otherwise .than pure 

 cotton on the coloring principles of cochineal, logwood and madder. 

 The action of solids in weakening solutions, he says, shows how filters 

 can act on substances which traverse them. O'Shea (188G) found that 

 lead salts are retained from their solutions on filtering through various 

 filter papers of English, German and French make. An experiment 

 shows that a Schleicher and Schiill filter No. 589, absorbed from 50 c.c. 

 of lead acetate, 0.12 mg. of lead, 0.02 mg. of which were removed by a first 

 washing, and none by a second. On refiltering, 24 mg. were absorbed, 

 none of which was removed on subsequent washing. 



Musculus (1870) showed that if urine in active alkaline fermentation 

 be filtered through paper, this paper, after having been washed until 

 the wash water is free from any alkaline reaction, and dried at 35°-40°, 

 retains even for months a something capable of exciting alkaline fer- 

 mentation of urea. This something, he considered to be "torulae" re- 

 tained in the pores of the filter. The subsequent washing which he 

 gave the paper with alcohol, it seems, must have killed any living cell 

 retained in the pores. Further, Miquel, as before mentioned, has 

 shown that urase is a soluble ferment. It is possible that the enzyme 

 was fixed by the filter paper. We have, by the following experiments, 

 shown that hardened filter paper fixes ptyalin. 



In an aeration tube, previously described, crumpled bits of hardened 

 filter paper were substituted for the glass beads, and 10 per cent, saliva 

 was aerated over this paper for 24 hours. Controls were made of un- 

 aerated saliva, and of saliva aerated over beads, side by side with the 

 paper aeration, and at equal rates of aeration. That aerated over glass 

 beads was found to be undiminished in activity after 24 hours aeration, 



