222 BIO-CHEMICAL JOURNAL 



explained by what 1 have called in the earlier part of this paper the 

 'law of adsorption.' In illustration I may cite one experiment : 



Two filter-papers of equal size (12 cm. diam.) were each cut into 

 eight pieces. Two flasks, each containing 50 c.c. of a dilute congo- 

 red solution were taken, and to one of these the whole of one paper 

 was added at once, to the other piece by piece at intervals of about 

 twelve hours. After all the paper had been added the amounts taken 

 up from the solution were : 



Added altogether ... ... ... 37% 



piece by piece at intervals ... 48 % 



It is advisable in this experiment to wait a considerable time 

 between the addition of each piece of paper on account of the slow 

 attainment of equilibrium in the case of congo-red and paper. 



7 . The part played in enyzme-action 



The interest of adsorption phenomena in this region is in 

 connection with the combination between enzyme and substrate, which 

 so much recent work indicates as an indispensable condition of attack. 

 The fact that enzymes are carried down when a colloidal precipitate is 

 produced in a solution containing them, has been long known and used 

 as a means of preparation. But whether the union between a more 

 or less specific enzyme and the body hydrolyzed under its influence is 

 to be looked upon rather as a true chemical combination is a matter 

 of dispute. 



Certain experiments have been made by Dauwe ' as to the taking 

 up of enzymes by colloids. These were done chiefly on pepsin and 

 various proteins, a few on the taking up of pepsin by agar and of 

 emulsin by coagulated egg-white. Dauwe comes to the conclusion that 

 the process is not one of adsorption, since the same weight of boiled egg- 

 white takes up the same amount of pepsin whether the egg-white is in 

 large pieces or fine powder. He considers that the hypothesis of solid 

 solution applies to the case better. It seems to me that this conclusion 

 is scarcely justified. Coagulated egg-white is not a homogeneous solid 

 body, but porous, like charcoal, and therefore its active surface must not 



I. Hofmeister's Seitrage, VI. p. 426, 1905. 



