ASPECTS OF ADSORPTION PHENOMENA 225 



c compound ' formed should prevent the appearance of trypsin in the 

 filtrate. This I find to be the case. It may be said that what we 

 have here is an instance of mutual action of colloids, but, as I think I 

 have been able to show in the previous pages, there is no essential 

 difference between this action and adsorption by solids from watery 

 solution. On the other hand, it might be held by some, that the case 

 is one of true chemical combination. To test this view I performed a 

 similar experiment, taking caseinogen and malt amylase, and found 

 that this enzyme is also held back by caseinogen, so that it appears to 

 be merely adsorbed. This interpretation of the union of enzyme and 

 substrate does not, of course, exclude a certain degree of specific 

 relation between a particular enzyme and the substrate hydrolyzed by 

 it, as we have seen there is considerable evidence of specific adsorption. 

 It is probable, moreover, that it does not hold, in the same degree, for 

 such enzymes as invertase, maltase, or lactase, when the substrate 

 hydrolyzed is not colloidal, and where there seems to be a very 

 close relationship between the chemical structure of the enzymes and 

 the bodies split by them. 



In another way the results described in the present paper are of 

 interest in connection with enzymes. I refer to the action of 

 electrolytes. From the work of Cole, 1 McGuigan, 2 and others, it 

 follows that there is a certain opposition between the action of kations 

 and anions. This indicates that enyzmes are possibly electrically 

 charged colloids. Victor Henri, 3 in fact, speaks of trypsin as a 

 negative colloid. 1 have tested the behaviour of a solution of 

 Grubler's trypsin in the boundary apparatus, and found that it does 

 indeed move to the anode, but how far this negative charge is due to 

 the enzyme itself it is naturally impossible to decide until we have in 

 our hands a pure preparation of the enzyme. 



It is possible, however, to attack the problem in another way. 

 Caseinogen in solution in alkali is electro-negative, if trypsin is also 

 negative neutral salts, and especially those of bivalent kations, such 



1. Journal of Physiology, XXX, pp. 202 and 281, 1904. 



2. American Journal of Physiology, X, p. 444, 1904. 



3. C. R. Soc. di Biologic, LIX, p. 132, 1905. 



