500 Profs. Percy Franklaud and Marshall Ward. 



From the above tables it is seen, that in the steam-sterilised deep 

 well water also the typhoid bacilli were incapable of multiplication, and, 

 on the contrary, undenoent continuous decline in numbers; they icerc 

 last discovered on 8.11.1893, or twenty days after their introduction, 

 whilst on 20.11.1893, or after being in the water for thirty-two days, they 

 were no longer discoverable by plate-cultivation. In this connection it 

 is particularly noteworthy that the typhoid bacilli were still dis- 

 covered on 21.11.1893 in the unsterilised deep well water, thus shoic- 

 ing that in this deep u-ell water their longevity was ^t,naffected by the 

 circumstance of whether the water was sterilised or unsterilised. In the 

 case of both the Thames and Loch Katrine waters, on the other 

 hand, the longevity of the typhoid bacilli was much greater in the 

 sterilised than in the unsterilised water. 



This circumstance is particularly instructive and important, inas- 

 much as it was just in this typhoid-infected unsterilised deep well 

 water that the water bacteria present multiplied most extensively, 

 and yet this large multiplication of the common water forms did not 

 prejudicially affect the typhoid bacilli. 



This deep well water, on the other hand, is in the sterilised con- 

 dition less favourable to the longevity of the typhoid bacilli than 

 the sterilised Thames and Loch Katrine waters, for in these three 

 steam-sterilised waters the introduced typhoid bacilli disappeared 

 first in the deep well and last in the Loch Katrine water, their 

 longevity in the steam-sterilised Thames water being greater 

 than in the deep well and less than in the Loch Katrine water. 

 (For further remarks on this behaviour see p. 517.) 



In the deep well water sterilised by filtration through porous por- 

 celain (in this case again infusorial earth), the typhoid bacilli again 

 disappeared with remarkable promptitude, being no longer dis- 

 coverable eleven days after their introduction. 



In order to ascertain whether these waters sterilised by filtration 

 through porous cylinders owed the rapid disappearance of the 

 typhoid and coli bacilli which almost invariably occurred in them to 

 the presence of any antiseptic substance possessing general bacteri- 

 cidal properties, the following experiment was made : 



The typhoid-infected porcelain-filtered deep well water referred to 

 above, and in which the typhoid bacillus was proved to be extinct on 

 30.10.1893, and 8.11.1893 respectively (see Table, p. 505), was on 

 11.11.1893 treated with three drops of the unsterilised uninfected 

 deep well water. These three drops of unsterile water must have 

 contained about 3000 water bacteria, as calculated from the results 

 of plate cultivation given in the table on p. 499, and, as the volume of 

 filtered water to which these three drops were added was about 

 100 c.c., the latter must have acquired about thirty water bacteria 

 per 1 c.c. by the addition. 



