336 MIORO-OKGANISMS IN WATER 



their destruction was not accomplished, for when 

 removed from the sunlight the hitherto clear liquid 

 became gradually turbid. In consequence of the con- 

 tradictor}^ results obtained by Downes & Blunt and 

 Tyndall revspectively, Jamieson ^ made a series of inves- 

 tigations in Melbourne, using Cohn's solution. This 

 worker found that the temperature of the solutions 

 when exposed to direct sunlight rose to as high as 

 51° C, and that this was by no means the highest point 

 reached. He, therefore, attributed the action of light 

 not to the sun's rays, but to the high temperature which 

 is thus produced in the solutions employed, a tempera- 

 ture which he declared to be sufficient in itself to 

 destroy the bacteria present. He further states that 

 when exposed during April to the sun's rays, when the 

 temperature of the solutions did not rise beyond 36° C, 

 the bacteria present were not destroyed. 



Downes and Blunt ^ replied to this criticism by sajdng 

 that, although some varieties of bacteria might doubtless 

 be destroyed through this high temperature, yet others, 

 and especially their spores, could certainly successfully 

 withstand a considerably higher temperature. 



It was evident that conflicting results would be 

 obtained as long as mixtures of micro-organisms were 

 the subject of investigation, and Duclaux,^ therefore, 

 attacked the question by employing pure cultivations of 

 bacteria. The particular form chosen was a fermenting 

 bacillus, Tyrothrix Scaber, obtained by this investigator 

 from milk, and was made use of for this purpose 



1 ' The Infl-aence of Light on the Development of Bacteria,' Natnre, 

 vol. xxvi., 1882, No. 663. 



2 ' On the Action of Sunlight on Micro-organisms, with Demonstration 

 of the Influence of Diffused Light,' Proc. Boy. Soc. vol. xl. No. 242, 1886. 



3 ' Inflnence de la Lnmifere dn Soleil snr la Vitalite des Germes de 

 Microhes,' Co7n])tes rendus hehdoviadaires des Stances de VAcadMnie 

 des Sciences de Paris, 1885, torn, c, p. 119, 12 Janvier. 



