274 MICRO-ORGANISMS IN WATER 



destroy tlie organisms other than typhoid in the water 

 itself, before proceeding to plate-cultivation. For this 

 purpose the water to be examined is introduced into a 

 test-tube containing sterile peptone-bouillon and five 

 drops of a 5 per cent, solution of phenol. The water 

 with this phenol-bouillon is then preserved at 42° C. 

 Most of the water-bacteria are thus removed, but Vincent 

 himself acknowledges that he was not able by this 

 means to eliminate the B. coli communis. 



Chantemesse and WidaVs Method} — This method 

 consists in using for the plate-cultivation of the water 

 under examination a gelatine-peptone medium contain- 

 ing "25 per cent, of phenol. Holz has shown, however, 

 and his results have been confirmed by Dunbar, that 

 these authors used a percentage of carbolic acid, which 

 altogether prevents the growth of the typhoid bacillus ; 

 and Dunbar has further shown that small additions of 

 phenol, by impeding the growth of the colonies of 

 B. coli, cause the latter to present even stronger resem- 

 blances than usual to the colonies of the typhoid bacillus. 

 Dunbar has also made experiments which confirm Vin- 

 cent's observations, that the B. coli communis is able to 

 withstand a larger addition of phenol than the typhoid 

 bacillus, so that even if a smaller amount of phenol 

 were to be used than that recommended above by 

 Chantemesse and Widal in their paper, no advantage 

 would be gained, as, along wdth the typhoid bacillus, 

 the B. coli communis must, if present, also invariably 

 make its appearance. 



Dunbar has further pointed out that the addition of 

 ^-^ c.c. of a 5 per cent, solution of phenol to 10 c.c. of 

 gelatine— i.^. a gelatine containing 0'05 per cent, phenol, 

 exercises a marked effect in reducing the liquefaction of 

 the gelatine by foreign organisms, whilst this addition 



^ Gazette des Hopitaux, 1887, p. 202. 



