483 



One can therefore conclude th-a^t in this way an idea can be 

 obtained of tlie quantity of enzyme vvliich is present in certain 

 fluids. This only holds good on condition that these fluids have for 

 the rest tjuile the same composition. Now it has unfortunately to f)e 

 stated that the culture-fluid of each fungus changes in the course 

 of the development, partly because certain bodies from (he fluid are 

 taken up by the developing mycelium, partly also in consequence 

 of secretions by the fungus. 



In this respect therefore the cultures of Aspergilhis at diflterent 

 stages are not quite comparable. The concentration of the H-ions 

 could be made equal, by the addition of acid or alkali, but that 

 would not completely meet the case, because other bodies may 

 certainly be present which hasten oi' letard the reaction and which, 

 at least at the present time, cannot be determined. 



There is indeed another method conceivable which would consist 

 in mixing culture-fluids of different stages with one anothei-, after 

 part of them had been boiled to destroy the enzyme. By this means 

 one would then be able to trace whether in a given solution sub- 

 stances were present which hasten or retard the enzyme-action. 

 From some preparatory experiments it appears that something may 

 perhaps be obtained by such a method. So, for example, the 

 fungus from a culture 7 days old, was finely ground up, and then 

 extracted with its own culture-fluid, and the solution was then diluted 

 with an equal volume of a. its own culture-fluid, after this had 

 been boiled to destroy its enzyme, h. a culture-fluid similarly boiled 

 from a culture which was 17 days old, and" c. a like solution of a 

 culture which was 8 days old. On investigation it was found that 

 when 5 c.c. of the above mentioned solutions were mixed with 

 5 cc. of a solution of soluble starch of 0.087o. ^^20 minutes elapsed 

 in the cases of a aiul b before all the starch had disappeared, whilst 

 in the case of c, this period amounted to 900 minutes. Hence there 

 was in v either present an accelerator, or the solutions a and b 

 contained retarding substances which were wanting in c. For the 

 rest this method was not worked out further on account of I he 

 condition mentioned at (he beginning of this paper, and the figures 

 obtained must therefore be received with a certain lesorve. It will, 

 however, be seen that they nevertheless give some idea of the course 

 of the formation of diastase in Aspeiyillns iilyer. 



Before 1 further menlion the results of (he investigation I will 

 first indicate by means of an exanq)le, exacdy how the figures were 

 obtained. Three flasks, each containing 75 c.c. of culture-fluid were 

 investigated, after a culture of Asperyillas niger had been in them 



32 

 Proceedings Royal Acad. Amsterdam. Vol. XXI. 



