908 ON THE EXAMINATION OF WATER FROM THE SYDNEY SUPPLY, 



Representatives of all these groups of bacteria may be contained 

 in or transported by drinking-water, which, on account of its being 

 a liquid, constitutes an admirable vehicle for them. 



Some importance, therefore, ought always to be attached to 

 the testing of potable waters for bacteria, more especially since 

 plain and convenient, and at the same time, satisfactory methods 

 of research are now at our disposal. In cases and at times of 

 epidemics especially, for instance of typhoid fever, such inquiries are 

 undoubtedly extremely useful, as they may supply us with facts, 

 otherwise scarcely or not attainable. 



The water which formed the subject of the present examination 

 was pipe- water from the Sydney supply, and was derived, in nearly 

 all cases, from the tapjua the laboratory at the Linnean Hall ; one 

 sample only was obtained from a tap in Mr. Macleay's house. 



The remarks made in this paper on the condition of that water 

 as regards the bacteria found in it, do not by any means pretend to 

 be exhaustive ; they are, in fact, but the results of some observa- 

 tions briefly relating to the quantity, and some characteristic 

 features of the micro-organisms hitherto obtained, and they 

 will in time, I hope, be followed by data of a more comprehensive 

 nature. 



Methods of Examination. 



In examining the water under consideration I employed Koch's 

 method, with which I had ample opportunity of making myself 

 acquainted in Germany during the year 1885. The principle which 

 underlies this method, and in which it so materially differs from all 

 other methods relative to the same subject — I shall do well to state 

 that here in a few words — consists in the application of a solid and 

 at the same time transparent, nutrient soil for the cultivation of 

 vegetable micro-organisms in their pure state, i. e. not mixed with 

 foreign elements. In this respect, the most universal cultivating 

 medium, as used by the school of Koch, is a 5%-10% meat-broth- 

 peptone-gelatine, or shortly nutrient gelatine, which is still solid at 

 a temperature of 25° C. (77° F.) This nutritive gelatine — I need 

 scarcely say here that j^in conducting pure cultures a thorough 

 sterility of all substances and apparatus used, is a conditio siite 



