221 



he only used two différent kinds of nutrient bases, we must be 

 cautlous in accepting the conclusions he drew from his results. 



Poitevin in 1902 investigated the sécrétion of lactase by .4 S;^g;'- 

 gillus niger, and he found that lactase was only secreted when the 

 spécifie reaction of that enzyme could take place. 



Dox thinks, after his investigations on Pénicillium cafnemherii 

 in 1910, that ail the enzymes, which an organism is capable of prod- 

 ucing, are secreted at ail times; that therefore nutrition only has 

 a quantitative influence on the sécrétion of enzymes and that the 

 more of a given enzyme is needed, the more is secreted. Colin 

 1911 and Grezes 1912 are of the same opinion. 



In 1911 K y 1 1 n investigated thls matter more fully, but he did not 

 succeed in throwing any further light on the subject. He cultivated 

 fungi on several substances, always with the addition of starch, and 

 from day to day tested whether any starch was left in the culture 

 solution. The more sugar there v^^as m the solution, the longer the 

 starch took to disappear. As soon as this happened, he considered 

 the expenment as ended. He found that diastase production took 

 place even in culture solutions without starch, and always found 

 this the case in the many différent foodmatenals he used. In ail 

 thèse cases diastase was formed ; when however starch was added 

 to thèse culture solutions, more diastase was produced, and stiU 

 more when starch was the only available foodmatenal. Kylin con- 

 siders this to be a very good instance of the quantitative mfluence 

 of nutrition on enzyme sécrétion. 



AH thèse researches hâve a common source of error: no attention 

 was paid to the âge of the fungi m question. Yet we can scarcely 

 imagine that a fungus will secrète the same quantity of enzyme 

 throughout its whole lifetime; on the contrary, it is possible that 

 a certain quantity is formed and later on disappears for some, as 

 yet, unknown reason. In any case, we are not entitled to compare 

 the results of two experiments in which organisms of différent âges 

 hâve been used. Thèse theoretical considérations caused Went in 

 1914 to investigate the sécrétion of diastase by Aspergillus niger 

 durlng its whole lifetlme. As a culture solution he used a 5^o solu- 



