518 Profs. Percy Fraukland and Marshall Ward. 



discovered which are injurious to, or destructive of, B. typhosns, but 

 I have not yet succeeded in establishing the fact." 



It naturally suggests itself that possibly the particular kinds of 

 water bacteria present in the three different kinds of water experi- 

 mented with may have influenced the relative longevity of the 

 typhoid bacillus in these three waters respectively. With a view to 

 putting this supposition to the test, the following series of experi- 

 ments were made : 



(a.) One portion of the typhoid-infected steam-sterilised Thames 

 water was inoculated with a few drops of unsterilised Thames 

 water, a second portion with a few drops of unsterilised Loch 

 Katrine water, and a third portion with a few drops of un- 

 sterilised deep well water. 



(6.) One portion of the typhoid- infected steam-sterilised Loch 

 Katrine water was inoculated with a few drops of unsterilised 

 Thames water, a second portion with a few drops of unsteri- 

 lised Loch Katrine water, and a third portion with a few drops 

 of unsterilised deep well water. 



(c.) One portion of the typhoid-infected steam-sterilised deep well 

 water was inoculated with a few drops of unsterilised Thames 

 water, a second portion with a few drops of unsterilised Loch 

 Katrine water, and a third portion with a few drops of unsteri- 

 lised deep well water. 



Unfortunately, this series of experiments was only commenced on 

 16.11.1893, when the number of typhoid bacilli in the three steam- 

 sterilised waters had got very low (see Tables, pp. 501, 503, 505). In all 

 instances there was an enormous multiplication of the water bacteria 

 introduced in the few drops of unsterilised water added in each case, 

 but owing to the small number of typhoid bacilli present, it was not 

 possible to establish whether the rate of their disappearance was 

 differently affected by the multiplication of the water bacteria from 

 the unsterile Thames, Loch Katrine, or deep well water respec- 

 tively. 



Owing to the failure of the above series of experiments to deter- 

 mine whether the undoubtedly greater bactericidal properties of the 

 unsterilised over the sterilised waters are due to the multiplication of 

 the contained water bacteria, or to some other cause, the following 

 fresh series of experiments was conducted on Thames water alone 

 with the object of elucidating the same point. 



