242 MICROORGANISMS IN WATER 



the C0 2 they were present in countless numbers. Some 

 experiments were also made to ascertain if the degree 

 of pressure employed produced any bacterial effect, but 

 from the results obtained it would seem that it does 

 not play any important part, the capricious variations 

 in the bacterial contents being attributable rather to 

 other causes. 



It is obvious, therefore, that our knowledge con- 

 cerning the influence of carbonic anhydride on the 

 multiplication of the micro-organisms normally present 

 in water is still in a far from satisfactory condition, 

 although, taking the whole evidence into consideration, 

 there appears to be little doubt that the multiplication 

 of most forms is retarded, if not altogether inhibited, 

 by this gas, whilst other forms are either capable of 

 withstanding its destructive influence, or of actually 

 multiplying in its presence. Fortunately our informa- 

 tion concerning the deportment of some pathogenic 

 bacteria in carbonated waters is more definite and less 

 contradictory, but to this we shall refer specially in 

 the tables in Chapter VIII. 



The action of ozone on bacteria in water has been 

 made the subject of some important experiments by 

 Ohlmiiller. 1 The ozone employed was generated from 

 atmospheric air by means of Siemens tubes as modi- 

 fied by Frohlich (Elektrotechnische Zeitschrift, 1891, 

 Heft 26). Although ozone in the dry state has very 

 little effect upon bacteria, when employed in a moist 

 condition it acts as a very powerful bactericide ; thus, 

 in the following experiments the ozonised air was 

 bubbled through water in which the bacteria were 

 suspended : 



1 ' Ueber die Einwirkung des Ozons auf Bakterien,' Arbeiten a. d. 

 Tcaiserlichen Gesundheitsamte, vol. viii., 1892, p. 229. 



