iv.] ARTIFICIAL COMMA-BACILLI. 71 



ture, the first indications of the colonies of the comma-bacilli 

 make themselves visible as small round depressions some- 

 what greyish in colour. In another day each colony is a 

 circular or oval, translucent or pearly-looking speck from the 

 size of a millet seed to that of a small pea ; the smallest when 

 looked at obliquely still show the central pit, surrounded by a 



FIG. 24. A COLONY OF CHOLERAIC COMMA-BACILLI IN GELATINE, PEVENTY-TWO 

 HOURS OLD. MAGNIFIED 170 TIMES. FROM A PHOTOGRAPH AFTER KOCH. 



greyish areola of liquefied gelatine, the larger ones showing no 

 central pit but a white granule in the centre, while the areola 

 of liquefied gelatine is greyish and translucent. Under a 

 magnifying glass this greyish liquefying colony appears more 

 or less uniformly and finely granular. In another day, while 

 the colony enlarges in diameter considerably larger than is 

 stated by Koch, its outline is still smooth, circular or oval, 



