284 MICRO-OKGANISMS IN WATER 



ing water, whilst the spores of anthrax in their normal 

 state will withstand such temperatures for a consider- 

 <*:i,ble length of time. In order to turn these properties 

 to practical account, portions (1 c.c. or 3 c.c.) of the 

 water supposed to contain anthrax spores are mixed 

 with a little sterile broth (1 c.c), and heated for periods 

 of two or five minutes to 50° C, to 70° C, or to 90° C, 

 after which treatment they are submitted to ordinary 

 plate cultivation. As an illustration of the manner in 

 w^hich this method works the following example may 

 be cited : — Thames water, purposely infected with 

 anthrax spores, and containing upwards of 100,000 

 water bacteria in 1 c.c, had this number reduced after 

 heating as above for five minutes to 50° C. to from 

 thirty-five to thirty-nine per c.c, amongst which several 

 ■of the colonies on the plate were recognisable as those 

 of anthrax. Again, on the same day, other portions of 

 the same water were heated to 70° C. for two minutes, 

 after which only from ten to thirty colonies per c.c. 

 made their appearance, amongst which from four to ten 

 were recognisable as anthrax. Other portions of the 

 same water were heated on the same day to 90° C. for 

 two minutes, with the result that only from seven to ten 

 colonies per c.c appeared, of which from three to six 

 were found to be anthrax. 



By this simple method the water is deprived of its 

 rapidly liquefying forms, which so quickly render the 

 gelatine-plate fluid and necessitate its being thrown 

 -away before the more slowly developing anthrax colo- 

 nies have been able to make their appearance* Such a 

 water, swarming originally with water bacteria, may 

 thus be easily examined, and the anthrax colonies identi- 

 fied by gelatine-plate cultures. 



The longer the bacteriological examination of water 

 is practised the more evident does it become that in 



