Surface Tension and Ferment Action. 



579 



unchanged when surface tension ceases to operate. The action of this 

 component would be in accordance with the first alternative suggested above, 

 namely, that surface tension acts as a brake on the chemical process which 

 proceeds in the substrate under the influence of the ferment. 



The action of the second component involves a permanent alteration in the 

 system cane sugar-invertase. How is the action of this component to be 

 interpreted ? 



We have considered hitherto only the possibility that surface tension 

 inhibits the second phase of an enzyme action, namely, the chemical change 

 which proceeds in the substrate after it has become combined with the 

 enzyme. We may now examine what effect surface tension could have on 

 the first phase of an enzyme action — the combination of enzyme and 

 substrate. The question is then : Is it a priori possible that surface tension 

 could inhibit the combination of enzyme and substrate, and if so, how can 

 this possibly be tested experimentally ? 



It is a well known fact that ferments tend to go into the surface layer, so 

 that the concentration of the ferments is higher on the surface layer than in 

 the remainder of the solution. This property of ferments is expressed by the 

 statement that ferments are " surface active." By increasing the surface, 

 therefore, more ferment will be driven into the surface layer. Cane sugar, 

 on the other hand, is practically not surface active, and its distribution in the 

 solution will, therefore, remain unaltered when the surface is increased. 

 Theoretically, therefore, it would seem possible that by extending the surface 

 a certain amount of invertase is driven into the surface and thus prevented 

 from combining with the cane su^ar. 



The point is capable of being tested experimentally. If new surfaces are 

 created the ferment is, as just stated, driven into the surface layer. If, for 

 instance, a ferment solution is shaken so that foam is formed, the concen- 

 tration of the ferment in the foam is greater than that in the rest of the 

 solution. If now the foam is allowed to subside, the concentration of the 

 ferment in the solution rises again, although the original value may not be 

 reached. But if new surfaces are created by the introduction of solid 

 substances, a second phenomenon may come into appearance. The ferment 

 not only goes into the surface layer bounding the solid, but may become 

 adherent to the solid, so that when the new surfaces are destroyed by with- 

 drawing the solid, the ferment remains adherent to the solid and is withdrawn 

 with it. 



This is the phenomenon of adsorption, which is exhibited in a marked 

 degree by a number of ferments brought into contact with solids such as 

 charcoal, collodion membranes, suspensions of mastix. It is not necessary to 



VOL. LXXXVIII. — B. 2 Y 



