434 A MANUAL OF BACTERIOLOGY 



vibrio stains well with the ordinary anilin dyes, especially 

 with dilute carbol-fuchsin, but is decolorised by Gram's 

 method. It is actively motile, and typically possesses a 

 single terminal nagellum at one end only, but there is some 

 variation in this respect. Spores are not formed, though 

 in old cultures Hueppe described bodies which he believes to 

 be arthrospores. In such cultures the bacilli lose their regular 

 shape, and swollen and distorted involution forms are seen. 



The majority of the organisms in a young agar culture 

 assume the vibrio form, but in broth or peptone water 

 cultures two or three days old they are longer and there 

 is a tendency for them to become somewhat spirillar. 



Cultural characters and biology. The Koch vibrio is 

 aerobic and facultatively anaerobic, and grows well on 

 the ordinary culture media from 20 to 37 C. It grows 

 readily in an atmosphere of hydrogen, but does not develop 

 in one of carbonic acid gas. 



In gelatin plates at 22 C. small cream-coloured colonies 

 appear in about twenty- four hours, soon accompanied by 

 liquefaction, so that in two or three days the plate becomes 

 pitted. Microscopically, the young colonies are rounded 

 with irregular margins, cream-coloured, and coarsely 

 granular. In stab- cultures development occurs all along 

 the stab as a whitish, opaque, punctate growth, thicker 

 above than below. Liquefaction commences about the 

 second day and progresses slowly ; in the early stage 

 it is confined to the surface, and looks like a little bead or 

 air-bubble (Plate XVIII. b), but in a fortnight or so the 

 greater part of the gelatin may be liquefied. Liquefaction 

 varies greatly both in rate and in extent in different 

 cultures and stocks ; in some old laboratory cultures it 

 may be almost absent. On surface agar a thick, moist, 

 shining, greyish growth quickly develops with more or less 

 crenated margins, often becoming brownish when old. On 

 blood- serum much the same growth occurs with slow 



