153 
Microbiology. — “Action of hydrogenious, boric acid, copper, man- 
yanese,. zinc and rabidium on the metabolism of Aspergillus 
niger”. By Mr. H. J. Warrrman. (Communicated by Prof. M. 
W. BeIJERINCK). 
(Communicated in the meeting of Oct. 26, 1912). 
Raviin’s object when examining the culture conditions of Asper- 
gillus niger*) was to obtain the greatest possible weight of mould. 
The experimenters who after him occupied themselves with this 
question, likewise only considered the dry weight. 
Such an investigation must needs be partial as the process of the 
metabolism is only roughly determined by the weight of mould. For 
a good insight into this process it must be observed that for instance 
the spore formation produces differences in the chemical composition 
of the obtained mould materials. 
Hence, the changes of the plastic aequivalent or of the assimi- 
lation quotient should be determined many times in the course of 
the development; first of all of the carbon then of the otber elements. 
In an earlier paper’) | proved that changes of temperature and 
concentration do not modify the metabolism of the carbon and that 
only the velocity of this process is subject to modification. 
At present I have studied the influence of various chemical 
compounds. 
1. Action of different rates of hydrogenions. 
The results of the referring experiments are found in Table I. 
We see from it in connection with the incorrectness of these 
observations, caused by the small quantity of mould, that the plastic 
aequivalent of the carbon, in spite of the slackening of the growth 
and sporeforming, caused by the hydrogenions, does not undergo 
a convineing change. 
2. Action of different boric acid concentrations. *) 
Analogous results as for the hydrogenions were found with boric 
acid as seen in Table II. 
In lower concentrations of about 0,06°/, the plastic aequivalent 
remains almost unchanged. 
The slight lowering observed at higher concentrations may be 
(=) 
1) J. RAULIN, Etudes chimiques sur la végétation, Paris 1870. 
) H. J. Warerman, Beitrag zur Kenntnis der Kohlenstoffnahrung von Asper- 
gil/us niger, Folia Microbiologica, Holliindische Beiträge zur gesammten Mikrobiologie 
1912 Bd. T p. 422. 
3) Also compare: J. BörseKeN and H. J. WaTerRMAN, Folia Microbiologica [ (1912) 
p. 342. 
