Report on the Bacteriology of Water. 



545 



Katrine, and least in the deep well water, and intermediate between 

 the two in Thames water. Of these three waters, also, the Loch 

 Katrine contains the most, the deep well the least, and the Thames 

 an intermediate amount of organic matter. Not improbably these 

 circumstances are connected together. 



4. The experiments distinctly show that in these steam-sterilised 

 potable waters a summer temperature of 19 C. is more prejudicial 

 than a winter temperature of 6 8 C. to the duration of life of the 

 typhoid bacillus. 



5. Inasmuch as the numerical estimation of typhoid bacilli in 

 unsterile potable waters is practically impossible, the duration of 

 life of the typhoid bacilli in such waters has alone been made the 

 subject of study. This enquiry has involved an enormous amount of 

 labour, as the certain detection, by means of the special methods em- 

 ployed, of the typhoid bacillus, even in a single specimen of water, 

 may entail work extending over several weeks. The duration of life 

 of the typhoid bacilli introduced into the various unsterile waters in 

 the several series of experiments was as follows : 



Description of unsterile water. 



Thames water (11.5.1893) kept at 68 C. 



,, 19 C. 



Loch Katrine water (4.7.1893) kept at 



68 C. 

 Loch Katrine water (4.7.1893) keot at 



19 C. 



Loch. Katrine water (7.7.1893) kept at 



68 C. 

 Loch Katrine water (7.7.1893) kept at 



19 C. 



Thames water (19.10.1893) kept at 



912 C. 

 Loch Katrine water (19.10.1893) kept at 



9 12 C. 

 Deep well water (19.10.1893) kept at 



12 C. 

 Thames water (16.1.1894) kept at 



912 C. 



Duration of life of typhoid bacillus. 



> Between 25 and 34 days. 



Upwards of) Only a small number of 

 17 days I typhoid bacilli was in- 



Between 4 f troduced into these 

 and 11 days J waters. 



f Upwards of 14 days, after which, no 



) further examinations were made. (A. 

 much larger number of typhoid bacilli 

 was introduced in this than in the 

 above experiments.) 



Between 9~") Typhoid bacilli from one 



and 13 days 

 Between 19 -, uuu 



and 33 days j bers were 

 Between 33 | into each 



and 39 days J 

 Between 20 and 27 days. 



and the same source 

 and in the same nuin- 

 introduced 

 of these 

 waters. 



On comparing this table with that given under No. 3 above, it will 

 be seen that in all cases, excepting one, the duration of life of the 

 typhoid bacillus was greater, and often much greater, in the steam- 

 sterilised than in the corresponding waters unsterilised. The single 

 exception to this general rule was in the case of the deep well water 

 in which the typhoid bacilli lived about the same length of time, 

 irrespectively of whether the water was sterile or not. 



The table also shows that, as in the case of the steam-sterilised 

 waters, the exact length of time that the typhoid bacilli endured 

 residence in one and the same type of unsterilised water was subject 



