( 498 ) 
difference was to be explained by admitting that the enzyme of 
Polygonum is more soluble in water than that of Indigofera and 
so, during the extraction could perhaps in higher concentration act 
on the indican. But the experiment showed that this is not the 
case. Neither can the acid reaction of the juice of Polygonum, 
caused by kalium bioxalate, account for this difference, as the 
addition of this salt, kalium biphosphate, or of a little acid, to the 
materials used for the preparing of the enzyme from Indigofera, 
produces no change in the course of the phenomena. The addition. 
of asparagine is likewise without effect. Nor is the explanation to 
be found in the relation of both enzymes to the temperature. I have 
so come to the conclusion that in Polygonum part of the indican 
is decomposed by the direct action of the living protoplasm itself. 
This part is however small, and by quickly immersing in boiling 
water the protoplasm is killed before it causes decomposition. 
In the preparation of indigo-enzyme from Phajus grandiflorus 
nothing particular is observed. But we saw before that the decoction 
method produces no indican but indoxyl from this plant. 
As the figure below shows that the enzyme of Phajus becomes 
inactive already at a lower temperature (67° C.) than that of Indigo- 
fera (75° C.), I must admit that also in the leaves of Phajus kata- 
bolism exists together with enzyme action and that, at the immer- 
sion in boiling water, simultaneously with the dying of the proto- 
plasm, this katabolism causes a vigorous indican decomposition '). 
Hence Polygonum and Phajus agree in so far as in both indigo- 
fermentation is caused by katabolism and by enzymes; but they 
differ in the fact that in Phajus the katabolism is quickened by high, 
in Polygonum by low temperature. In Indigofera katabolism seems 
not to occur at all and the decomposition of indican appears exclu- 
sively eftected by the enzyme. 
From the preparations obtained in the way described, the enzyme 
itself can but be imperfectly extracted. In water it proves almost 
quite insoluble, somewhat better in glycerine and best of all in 
a 10 pCt. solution of common salt, as was already indicated by 
Mr. HAZEWINKEL, and in a 10 pCt. solution of calcium chloride. 
In these solutions only a small quantity of enzyme is soluble, for 
the remaining substance is nearly as strongly active as before the 
extraction. In the solutions themselves alcohol produces hardly any 
precipitate, so that more active preparations cannot be procured in 
1) In § 3 p. 513, will be demonstrated that all the indican is localised in the 
rotoplasm. 
Ei 
