SPIRILLA RESEMBLING CHOLERA. 449 



produces indol, and is highly pathogenic for rabbits, 

 guinea-pigs, pigeons, and mice. 



Spirillum Bonhoffi. — This organism (Fig. 102) was 

 found in water by Bonhoff. It has a decided resem- 



FlG. 102. — Spirillum Bonhoffi, from a culture upon agar-agar ; x IOOO (Itzerott 

 and Niemann). 



blance to the cholera spirillum, but is rather stouter 

 and less curved. Curved forms — i. e. semicircles, sig- 

 moids, and spirals — occur in old cultures especially. 



These organisms are colored badly with ordinary stains, 

 dahlia seeming to be the most appropriate color, and ac- 

 complishing the process better if warmed. The organ- 

 ism is motile, and has a long flagellum attached to one 

 end. 



The colonies develop slowly upon gelatin plates, first 

 appearing in forty-eight hours as little grayish points. 

 The margin of the colony is sharply circumscribed ; the 

 interior is broken up. The gelatin is not liquefied. In 

 gelatin punctures there is no liquefaction observable. 



Upon agar-agar the development at the temperature 

 of the incubator, which is more rapid than that at the 

 temperature of the room, results in the production of a 

 bluish-gray layer. 



The growth upon potato has a brownish color. The 



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