THE CHOLERA VIBRIO 531 



corpuscles added to quantities of a three-day-old broth 

 culture varying from O'Ol c.c. to TO c.c. (the smaller 

 quantities made up to 1 c.c. with saline), the mixtures 

 incubated for two hours at 37 C., and then kept in the 

 ice chest over night, found that not one of 333 different 

 strains of the cholera vibrio haemolysed, while of 100 

 cholera-like vibrios nineteen gave no haemolysis, sixteen 

 gave a trace of haemolysis, and the remaining sixty-five 

 hsemolysed more or less strongly. Grown for twenty -four 

 hours on 12 per cent, goat's blood-agar plates, of 161 

 cholera vibrios, one gave distinct, nine gave a trace of, 

 and the remainder no, haemolysis, while of forty-three 

 cholera-like vibrios, one gave no, one gave a trace of, and 

 the remainder gave decided, haemolysis. 



The cholera vibrio retains it vitality in cultures for a 

 month. It can multiply in water and on the surface of 

 moist linen, but rapidly dies on drying. Its thermal 

 death -point is about 55 C. with an exposure of ten 

 minutes. It is easily destroyed by the ordinary germicides. 



Dempster found that the comma bacillus lived from 

 three to five days in dry soil, but only one day in an 

 artificially dried soil, while in moist soil it lived from 

 twenty-eight to sixty-eight days. In peat, however, it 

 was invariably dead within twenty-four hours. In 

 sterilised salt solution (0-75 per cent.) the comma bacilli 

 were alive on the 159th day, and in fresh urine (sterilised) 

 they lived fourteen days at 37 C. and twenty-nine days 

 at 22 C. 



Greig found that in Calcutta in the stools kept at room- 

 temperature, the vibrio lived for just over one day in 

 June (hot season) and for just under eight days in 

 February (cold season). 



In sterilised distilled water the cholera vibrio usually 

 rapidly dies, as a rule within twenty-four hours. The 

 addition of sodium chloride greatly increases the length of 



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