536 



NOTE ON THE BACTERIOTOXIC AC I'lON OF WATER, 



A sewage-effluent was obtained through the kindness of Dr. 

 Stokes, Medical Officer to the Metropolitan Water and Sewerage 

 Board, and tested in a similar manner. The sample was received 

 on the 7th of October, 1913, when it was examined. It was then 

 stored in a laboratory cupboard for a fortnight and again tested. 

 It contained 90,000 bacteria per c.c. on October 21st. The 

 temperature during storage was 22°. 



Experiment iii. 



Date. 



October 7th . 

 October 21st 



Arerage 



100 cells of Bac. prodigiosus became 



Unboiled 

 effluent 



400 

 463 



431 



Boiled effluent. 



15 minutes. 60 minutes 



86 

 41 



63 



31 

 35 



33 



The unboiled, filtered effluent was nutritive to Bac. prodigiosus, 

 and the boiled effluent was decidedly toxic. 



While Bac. prodigiosus has been taken as an organism capable 

 of indicating the existence or otherwise of the toxic or nutritive 

 effect, it appeared advisable to test Bac. typhi. Accordingly, 

 cultures of two strains were obtained from Dr. Cleland, of the 

 Board of Health, and the previous experiments with tap- water 



were repeated. 



Experiment iv. 



Bac. typhi is very susceptible to the action of tap- water, which 

 is toxic to it; and, as in the previous experiments, boiling in- 

 creased the toxicity. 



