CUL TIVA TION. 381 



one which is irregularly granular or furrowed ; as they 

 become larger their surface has an appearance which has 

 been compared to fragments of broken glass. Later, lique- 

 faction occurs, and the colony sinks into the small cup 

 formed, the plate then showing small sharply-marked rings 

 around the colonies. Under the microscope the outer 

 margin of the cup is circular and sharply marked. Within 

 the cup the liquefied portion forms a ring which has a more 

 or less granular appearance, whilst the mass of growth in 

 the centre is irregular and often broken up at its margins. 

 Later still, liquefaction spreads around and the appearance 

 becomes less characteristic. The growth of the colonies in 

 gelatine plates constitutes one of the most important means 

 of distinguishing the cholera spirillum from other organisms. 



On the surface of the cigar media a semi-transparent greyish 

 white layer forms, which presents no special characters. On 

 solidified blood serum the growth has at first the same appear- 

 ance, but afterwards liquefaction of the medium occurs. On 

 agar plates the superficial colonies under a low power are 

 circular discs of brownish-yellow colour, and more trans- 

 parent than those of most other organisms. On potato at 

 the ordinary temperature, growth does not take place, but 

 when it is incubated at a temperature of from 30 to 37 

 C., a moist layer appears, which assumes a dirty brown colour 

 somewhat like that of the glanders bacillus. It has, how- 

 ever, a greyish -brown rather than a chocolate tint, and 

 moreover the appearance varies somewhat in different 

 varieties, and also on different sorts of potatoes. 



In bouillon with alkaline reaction the organisms grow 

 very readily, there occurring at 37 C. a general turbidity in 

 twelve hours, whilst the surface shows a thin pellicle com- 

 posed of the organisms in a very actively motile condition. 

 Growth takes place under the same conditions equally 

 rapidly in peptone solution (i per cent with .5 per cent 

 sodium chloride added). 



In milk also the organisms grow well and produce no 

 coagulation nor any change in its appearance, at least for 

 several days. 



