28 
F. F. Blackman. 
Present among the enzymes of these organs killed by freezing 
is also an oxydase enzyme which causes CO., to be given off when 
hydrogen peroxide is added to the extract. This effect is destroyed 
by heating the extract, and so is due directly to the oxydase; this 
makes a third category of C0 2 production, “oxydase C0 2 .” 
A recent paper by Chodat and Bach 1 provides a direct proof 
that an oxydase enzyme is actually at work in the living cell. One 
of the characteristic properties of such oxidising ferments is that of 
decomposing hydrogen iodide with the liberation of Iodine. If a 
drop of plant-extract containing oxydase be placed upon starch- 
paper, which has been dipped in Kl and dilute H 2 S0 4 and then 
dried, a blue spot is formed, due to the union of the liberated 
Iodine with the starch. It is now shown that exactly the same 
reaction can be brought about in the living cell. The cells of the 
peripheral part of a potato give an active oxydase extract; they 
contain starch and their sap is acid. If then KI could be intro¬ 
duced into the living protoplasm the starch should stain blue. 
When a thick section of potato is placed in dilute KI the cells are 
plasmolysed, but some of the iodide enters the protoplasm, and 
the starch actually does turn blue. That the protoplasm is not 
killed is shown by the fact that the cell recovers it turgor when 
placed in pure water. 
As further evidence it is shown that when pyrogallol diffuses 
into these same living cells, a reddish crystalline precipitate of its 
oxidation-product, purpurogalline, is quickly formed. 
There is thus a steady accumulation of evidence that each 
chemical change in the living cell is fostered and accelerated by a 
special enzyme. It is further now proved that these enzymes 
work efficiently after the cell is killed, and that their action 
is in no way vitalistic, but of a purely chemical katalytic nature. 
We may, then, turn now to consider what light physical chemistry 
can throw upon the mechanism by which the rate of enzyme 
activity is determined in the cell and maintained usually at a 
suitable biological intensity. 
Except for the presence of katalytic enzymes the various 
metabolic single changes would be too slow for biological con¬ 
tinuity. On the other hand, when accelerated by katalytic agents, 
they might easily go wastefully or even injuriously fast. This 
> Archives des Sciences physiques et naturelles, t. XVII., May, 
1904, p. 484. 
