750 BACTERIAL FLORA OF THE SYDNEY WATER SUPPLY, 



of alum and sodium carbonate to the water. The suspension is 

 centrifuged and the precipitate dissolved in a small quantity of 

 1-5% potassium hydrate; this does not affect the vitality of the 

 bacteria which are then cultivated. From 96 to 100% of the 

 micro-organisms present in the water can be obtained by this 

 method. 



The Sydney city water was tested by the various methods, and 

 the organisms that were brought into prominence by the in- 

 dividual schemes were studied in detail. Taken as a whole, the 

 bacterial flora that survives treatment with disinfectants is 

 limited. In the tests the water, as a rule, was passed through a 

 porcelain filter, and the bacteria brushed from the surface of the 

 candle with a sterile stiff brush into 10 c.c. of sterile water. 

 Various quantities of the suspension were used. 



The three methods of Vincent, Bandi, and Jordan are very 

 similar, and as the two latter are the more recent and improvements 

 upon the former, they alone were tried. By Bandi's method 

 the first tube of carbolised meat extract only became turbid, 

 succeeding tubes failed to show a growth. There was only one 

 kind of organism in the turbid tube. The temperature of 45° C. 

 appears to be too high for the growth of species of Bad. coli, 

 especially under such unfavourable circumstances as obtain in 

 carbolised media. As we shall see later, Bad. cull would be 

 present in the quantity of water employed, viz., 2000 c.c. In 

 using Jordan's method the plates containing the equivalent of 

 20 c.c. of water and upwards became turbid, and plates infected 

 with the growth from 20 c.c. and 200 c.c. grew similar colonies. 

 From these two suspicious kinds of colony were picked out. 

 They were suspicious because they appeared to produce acid in 

 the litmus-lactose medium. In the one case this appearance was 

 caused by the red colour produced by the organism itself, which 

 proved to be Bad. miniaceum. The other was a micrococcus 

 which appears to be Mic. pyogenes y albus. By raising the 

 incubation temperature to 42° C. no growth was obtained in the 

 tubes even with the equivalent of 800 c.c. of water. A repetition 



