37 
solution, gave only rise to a very slight decrease of urease activity. 
The cases of mannitol and glucose are illustrated by fig. 9. 
It will be seen, that the general nature of the curves is not 
changed by the addition of neutral substances, from which it can 
be inferred, that only the m in our fundamental formula 
x 
— dx = m ——— dt 
z+ ne 
is affected. 
If other substances absorbed the radiation like the hydrogen-ions, 
the shape of the curves would have been altered, tending with pro- 
gressive change to the logarithmic curve. 
The facts recorded above and the theoretical deductions might 
afford some explanation of at least a part of ONopERa’s observations’), 
that alcohols can increase as well as decrease the action of urease. 
The experiments of this author, however, were made without buffer- 
mixtures and without any estimations of the py, which in the 
absence of buffers must have varied enormously. Since the long 
duration of urease action in those undefined, but certainly rather 
alkaline, conditions, must have had a deteriorating inflnence on the 
urease, the more so, the higher the py, a neat interpretation of these 
results is rendered impossible. 
9. Reversion of the hydrolytic action of urease on urea. 
The generally accepted view of the synthetic action of enzymes, 
shared also by the present author, is, that one and the same enzyme 
is the active agent in breaking down as well as in building up its 
specific substrate. 
The conditions, however, which cause either of the two opposite 
activities to predominate, have as yet not been made clear. 
Some observations, made in the course of this study and a 
general consideration of the enzyme activity in living tissues, indu- 
ced the writer to venture the following hypothesis: 
Around an enzyme particle the substrate is broken down as long 
as the action, radiating from the enzyme, is vigorous enough. Weak- 
ened by spreading or by other causes, the same enzyme radiation 
produces the reverse process, synthesis. 
In the living plant and animal both activities of the enzyme are 
going on continuously under ordinary conditions as to concentration 
of substrate, temperature and acidity. As soon, however, as the tissue, 
1) Biochem. J. 1915, 563. 
