THE IRON-BACTERIA 389 



it is an obligate aerobic organism, and there is a tendency to 

 the formation of short rods. In the case of both organisms 

 the addition of iron-compounds is not essential to growth. If 

 we are to class them under a physiological group both can fitly 

 be included under the peptone-bacteria, as this substance seems 

 to be able to supply them with both the carbonaceous and 

 nitrogenous essentials for the elaboration of protoplasm. 



Artificial cultures of Crenothrix polyspora have been obtained 

 by Garrett and by Rossler. The accuracy of the latter 's 

 results have been challenged owing to the fact that attempts 

 along the same lines by other investigators have invariably 

 produced negative results. Rossler states that he has been 

 successful in cultivating Crenothrix on bricks to which a little 

 ferrous sulphate had been added. It is vety probable that 

 Rossler did succeed in making impure cultures of Crenothrix 

 and that the necessary food materials were supplied by organic 

 impurities on the surface and in the substance of the bricks. 

 He states that he obtained pure cultures, but it is difficult to 

 see from his description how this was possible. Still more 

 remarkable artificial cultures were obtained by Garrett, who 

 states that during the period when the growth of Crenothrix 

 became so overwhelming at Cheltenham he was able to obtain 

 artificial cultures. The cocci liberated from Crenothrix threads 

 offered no resistance to growth on a gelatine plate, on coagulated 

 cleared serum at 30°C, on potato, etc. There is also here a 

 want of conviction as to the purity of the cultures. No details 

 are given as to the methods adopted to secure pure cultures. 

 Whilst there cannot be any reasonable doubt that artificial 

 growths were obtained by these investigators, one hesitates 

 to accept without further proof that those growths which 

 appeared on serum, potato, etc., were due to Crenothrix, and 

 not to extraneous micro-organisms that had crept in as impuri- 

 ties. In the case of Crenothrix, as in the other two, the results 

 show that the source of energy is not the oxidation of ferrous 

 to ferric compounds, but is rather obtained from the absorption 

 of organic substances. 



The writer has obtained slight impure cultivations of Spiro- 

 phyllum ferrugineum, but the results are too scanty and in- 

 conclusive to form a basis for discussion. 



