Malachite- Green and the Physiological Activity of~B, coli. 193 



which produced acid in the same test media as the original cultures (which, 

 it may be remarked, had undergone no change when tested again at the 

 conclusion of the experiment), but the power to produce gas had been 

 completely lost, and could not be restored by repeated sub-culture in 

 sugar media. 



Coli B. — This organism had been comparatively recently isolated from 

 horse-dung, and was quite typical in every way. Beyond the change in 

 physiological activity, it showed scarcely any difference from the original 

 culture, except that, on microscopic examination, the presence of long 

 filaments was noticed, greatly in excess, both quantitatively and qualitatively, 

 of that usually associated with Bacillus coli. 



Coli A. — This organism was particularly included, because, though quite 

 typical, it had been kept in the laboratory for nearly four years, and was 

 showing a very slight but noticeable change in physiological activity. 



Besides the physiological change already mentioned, it showed profound 

 morphological and cultural variation. Colonies grew slowly (not appearing 

 before the fourth day) on gelatin or agar at 20°, and then appeared as large, 

 viscous, circular masses, consisting of a mixture of very long filaments and 

 short bacilli, together with a gummy cementing substance (see figure). By 

 no possible means could the presence of a mixture be detected, and there is 

 no doubt that the filaments and bacilli belong to the same culture. 



The action of the malachite-green, therefore, has been to produce an 

 organism from a typical Bacillus coli, which is neither physiologically, 

 morphologically, nor culturally a colon bacillus. 



The identity of the organism throughout the experiment is easily seen 

 from the character of the change produced, and the concomitant filamentous 

 growth and slime production are not without precedent. I have shown 

 elsewhere that Bacillus coli, when grown under certain conditions such as in 



