1914] Arthur W. Dox 227 



fifteen to twenty days. Zinc is, therefore, useftil but not indis- 

 pensable. 



This conclusion of Lepierre regarding the non-specificity of zinc 

 is, however, at variance with the more recent work of Javillier.^^ 

 This investigator maintains that zinc is absolutely necessary for the 

 normal growth of Aspergillus niger, but the amount required is 

 so small that it may be obtained by the fungus f rom the glass culture 

 flask. He finds that a culture in a Jena flask, with or without addi- 

 tion of zinc to the medium, shows a normal growth, whereas cul- 

 tures in Bohemian glass or quartz vessels give only a fraction of 

 the yield of fungus unless zinc is added. The following is a typical 

 protocoll of Javillier's experiments in this connection. 



Weicht of fungus in grams 



Bohemian Jena Quartz 



Control 0.352 1.861 0.291 



With zinc 1.780 1.736 1.624 



The remarkable effect of minute quantities of manganese was 

 reported by Bertrand. ^^ Raulin's medium ordinarily contains 

 traces of manganese as an impurity. Elaborate precautions were 

 taken by Bertrand in purifying the chemicals from manganese be- 

 fore making up the medium. The medium thus prepared did not 

 jaeld normal cultures, the mycelium remaining sterile. The addi- 

 tion, however, of 0.00001 per cent. of manganese accelerated the 

 growth and increased the yield of the fungus. This extraordinary 

 response to minute quantities of manganese must likewise be re- 

 garded as a phenomenon of catalysis. 



The absence of calcium from Raulin's medium is quite striking 

 in view of the fact that this dement is so necessary for the growth 

 and maintenance of life in animals and higher plants. Robert^'^ 

 found that calcium occurs in Raulin's medium as an impurity intro- 

 duced principally with the sucrose, which may contain as much as 

 2 mg. of calcium per 100 gm. Using a medium prepared from care- 

 fully purified materials free from calcium, he still obtained normal 

 cultures. With the addition of small amounts of calcium, however, 



25JaviIlier: Compt. rend., 158, 140-143 (1914). 



26 Bertrand and Javillier: Ibid., 152, 225-8 (1910) ; Bertrand: Ibid., 154, 

 3S1-3, 616-8 (1912). 



^'^ Robert: Ibid., 153, 1175-7 (1911). 



