914 ON THE EXAMINATION OF WATER FROM THE SYDNEY SUPPLY, 



a potable water, Professor Koch says (1): — "A large number of 

 micro-organisms indicates that the water has received admixtures in 

 a state of decomposition and loaded with micro-organisms, impure 

 tributaries, etc., which might contribute in addition to the many 

 harmless bacteria, also pathogenic forms, that is, infectious matter. 

 Experience thus far has shown that in good waters the 

 number of germs capable of development varies between 10 and 

 150. As soon as the number considerably exceeds this limit, the 

 water must be suspected of receiving contributions from polluted 

 sources. If the number reaches or exceeds 1000 I should not 

 permit its use as drinking water, at least not in time of a cholera 

 epidemic. The number 1000 is chosen by me as arbitrarily as has 

 been the case in selecting the limiting values in chemical analysis, 

 and I allow each one to change it according to his convictions." 



After these statements of Koch the particular tap-water of 

 the Sydney supply — yielding an average number of 421 bacterial 

 colonies in 1 ecru., for a period of little more than two months (see 

 above) — cannot be declared as good. 



Description of the bacteria. 



In what follows I shall briefly describe the forms of bacteria 

 hitherto obtained from the above-mentioned pipe-water. This 

 description relates : — 



(1). To the appearances of the bacteria under high powers of 

 the microscope. The specimens are taken from colonies on the 

 glass-plates, and examined both living and after having been 

 stained with Loeffler's alkaline methyleneblue-solution. 



(2). To the morphological features exhibited by the different 

 species 



(a), in their colonies on plates of gelatine, both with regard to 

 their naked-eye appearances, and to those visible and demonstrable 

 by the application of low powers of the microscope (70-122 diam. ', 

 transmitted light; [narrow diaphragm.] ) 



(1) The original text not being at hand, I quote a translation commu- 

 nicated in the "American Monthly Microscopical Journal." Vol. VII., 

 Washington, April 1886, No. 4, p. 64. 



