ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 147 
series of related compounds to follow their capacities of lowering 
surface tension. It is complicated, however, by some other properties 
of these agents to be referred to below. As was pointed out in the 
preceding report in connection with muscular contraction, surface 
energy is peculiar in having a negative temperature coefficient. If 
the inhibiting effect produced by saponin, etc., has the cause 
suggested it should be found to be greater at a low temperature, just 
as the degree of adsorption in general is well known to be greater at 
a low temperature. The present writer (1918) in experiments with 
saponin and with amyl alcohol showed that this actually was the case. 
A practical point of interest is the effect of alcohol on digestion. 
As far as the rate of action of the digestive enzymes on food is 
concerned all experimental evidence shows it to be a retarding one, 
and the reason is doubtless that given above. 
Remembering that the action of enzymes is a surface one it is 
clear that any agents affecting the state of dispersion must affect the 
intensity of action. Any agent which increases the degree of 
dispersion increases the total surface and hence the activity of the 
enzyme. ‘This factor comes in to complicate the case discussed above, 
since agents lowering surface tension tend to increase dispersion and 
thus to counteract the inhibiting effect. A particularly marked case 
is the accelerating effect of bile salts on the action of lipase, It was 
thought to be due to better emulsification of the oil used as substrate 
until it was found to be present also when soluble esters, such as 
ethyl acetate, were used. It seems, therefore, that it must be due in 
part to greater dispersion of the enzyme itself. 
The possibilities of complexity of action are obviously greater in 
the action of electrolytes, because we have in addition the intervention 
of electrical forces and the effects of electrical adsorption. Some of 
these may decrease, others increase, the state of dispersion, according 
to the sign of charge on the enzyme particles. In the investigation 
of the effects of substances added to solutions of enzymes we have 
then a multiplicity of factors to take int» account, so that analysis of . 
the phenomena is very ditticult and much further work is required. 
The experiments of Onodera (1915) are of interest in this connection. 
We may regard it as established that adsorption of substrate by 
enzyme particles is the controlling factor in the velocity of the 
chemical reaction that follows. But is this adsorption followed by 
chemical combination with the enzyme, forming an intermediate 
compound of an unstable nature which then breaks up into products 
different from those substances from which it was formed? In the 
majority of cases, the chemical change involved is one by which the 
elements of water are either added or removed, but this is not always 
the case. There is every reason to regard the effect of an enzyme as 
‘an acceleration of the rate at which a given system attains its equili- 
brium position, the final products being the same as those which 
would have been formed, very slowly, in the absence of the enzyme. 
There is no inherent difficulty in the view that the concentration on 
the surface results in the rapid attainment of equilibrium by increased 
mass action, in the same way as Faraday explained the platinum 
effect and as Denham regards the inorganic heterogeneous catalysts in 
general to produce their results. This last observer points out that 
