A STUDY OF SOME FACTORS INFLUENCING 
THE STIMULATIVE ACTION OF ZINC SUL- 
PHATE ON THE GROWTH OF ASPER- 
GILLUS NIGER. I. THE EFFECT OF 
THE PRESENCE OF ZINC IN 
THE CULTURAL FLASKS 
By R. A. STEINBERG 
Columbia University 
The increased growth of Aspergillus niger resulting from the 
introduction of zinc salts into the nutrient solution was first 
observed by Raulin (9). This observation was confirmed by 
Richards (10) in 1897, who noted also that other elements (Co, 
Ni, F, Fe, etc.) exercised an influence similar to that of zinc. 
The studies of these two investigators, as well as those of 
Ono (8), of Richter (11), and of others agree in that there is the 
greater growth in the presence of zinc, although the percentage 
increase the various authors obtained is not identical. 
In 1903, however, a publication by Coupin (2) appeared, in 
which this author came to the conclusion that the increased dry 
weights formed in cultures of Aspergillus niger through the addi- 
tion of zinc salts takes place only in impure cultures. The addi- 
tion of zinc is effective, in this investigator’s opinion, only in those 
cases in which there is an opportunity for the suppression of the 
activities of other organisms, whose presence in the Aspergillus 
niger cultures prevents the full development of this fungus. In 
pure cultures the maximum dry weight is obtained without the 
addition of zinc. 
Another interpretation of Coupin’s results has been suggested 
by Javillier (3)—namely, the introduction of zinc into the nutrient 
liquid through solution of constituents of the glass of the cultural 
flask. Javillier, indeed, states that with cultures in Jena glass 
(flasks of the same kind of glass were made use of by Coupin) the 
addition of zinc is unnecessary inasmuch as the maximum growth 
