Incipient Vitality. 33 
stimuli, even with those like gravitation, that do not appear to 
affect the protoplasm through a chemical mechanism. 
A regulating effect of mass of yet another order must now 
he mentioned. The rate of action of a hydrolytic enzyme might in 
theory be affected by the amount of water molecules available for 
uniting with the substance to be hydrolysed. As in practice such 
changes take place in aqueous solution only, there is an enormous 
excess of water-molecules always present, and the mass of the 
water never acts as a limiting factor and may be neglected. 
With an oxidising enzyme, it is the union of some substance 
with hydrogen-dioxide (or with a similar “active” peroxide) and 
not with water, that is accelerated by the katalytic agent. This 
active peroxide will not necessarily be present in excess, and may 
be a limiting factor. Its varying amount will then determine the 
amount of oxidation that is being performed, and regulation may 
be obtained in this way. There seems to be no doubt that an 
active peroxide is present in the normal cell to a certain extent but 
we are unacquainted with the precise mechanism of its formation. 
Chodat and Bach in their interesting and accurate study of 
oxidising enzymes previously referred to have shown how such 
effects of mass interact. They investigated the amount of pyro- 
gallol that could be oxidised by hydrogen dioxide to form purpuro- 
galline under the acclerating influence of an oxidising enzyme 
prepared from horse-radish. Varying amounts of (1) pyrogallol, 
(2) hydrogen dioxide and (3) the enzyme-extract were mixed to¬ 
gether, and after fourteen hours the crystalline, insoluble purpuro- 
galline was filtered off, washed, dried and weighed. A quite 
precise relation holds between the amount of it formed and the 
amount of that one of the three original substances which happens 
to be the limiting factor to the activity of the whole system. 
The following Table is compiled from their figures, and shews 
how the amount of the product may be regulated by the amount of 
either of the reacting substances. 
Experiment. 
A. 
B. 
C. 
D. 
E. 
F. 
G. 
H. 
Pyrogallol 
10 
10 
10 
10 
1-0 
10 
10 
20 
grm. 
H, 0 2 . 
10 
10 
10 
10 
0*8 
0-4 
01 
10 
cc. 
Enzyme 
•01 
04 
•os 
•10 
•10 
•10 
•10 
•10 
grm. 
Purpurogalline 
•02 
•08 
•16 
•16 
•16 
•08 
•02 
•20 
grm. 
