ATMOSPHERIC SPIRILLA 121 



Atmospheric spirilla. The spirilla occurring in the air. 

 have been described by Weibel. They usually generate 

 yellow pigment, according to the degree of intensity of 

 which there have been distinguished a Vibrio aureus with a 

 colour varying from golden to orange-yellow, a Vibrio flavus 

 of an ochre-yellow tint, and a yellowish-green Vibrio flaves- 

 cens. The individual spirilla frequently appear remarkably 

 thin, generally S-shaped, and without power of automatic 

 movement. Islets of an oval or whetstone form, or some- 

 times circular, develop on the gelatine plate; they are 

 sharp-edged and granular, and generate pigment in a few 

 days. There is no liquefaction. Thrust-cultures in gelatine 

 and superficial cultures on agar display also a copious 

 development of colour, which takes place only on the surface 

 of the former ; while on discs of potato there appears 

 a luxuriant pap-like deposit of a very pronounced tint. 

 Spirilla are decolorised by Gram's method. 



