Report on the Bacteriology of Water. 4 Do 



Simultaneous Infection with Typlwid of Thames, Loch Katrine, and 



Deep Well Water. 



Each, of these waters was, in this comparative series, simulta- 

 neously experimented with in the natural unsterilisecl state, also 

 after sterilisation by steam, as well as after sterilisation by filtration 

 through a porous cylinder composed of baked infusorial earth. These 

 nine different kinds of water were all infected at one time with the 

 same quantity of typhoid bacilli taken from one and the same culti- 

 vation. 



For this purpose an agar-cultivation of sixteen days' age, and 

 grown at 18 20 C., was employed. Forty needle loops were care- 

 fully taken from the surface of this cultivation and thoroughly 

 mixed by prolonged agitation with 50 c.c. of sterilised tap-water. 

 Of the water- attenuation thus prepared 4 c.c. were added to 1000 c.c 

 of each of the nine different kinds of water. ID this manner wasj 

 therefore, secured the equal infection both qualitatively and quanti- 

 tatively of each of the nine experimental waters. Each of these in- 

 fected waters was subdivided amongst several sterile flasks. Th0 

 mouths of these flasks instead of being plugged with cotton-wool, 

 were in this series of experiments simply covered with sterile 

 beakers, an arrangement which is in many respects preferable for 

 purposes of this kind. All these flasks, together with similar flasks 

 containing each of the three unsterilised waters not infected, were 

 placed in a dark cupboard in which there prevailed an almost uni*- 

 form temperature of 9 12 C. 



In this series of experiments, besides determining the relative 

 longevity of the typhoid bacilli in the several different types of 

 potable water, I have also endeavoured to ascertain the effect on the 

 bacteria of keeping the waters at rest and in motion respectively. 

 To this end, in the case of each water, one flask was kept at rest and 

 only shaken up when a sample was to be taken from it, whilst the; 

 other flask was daily submitted to violent agitation over a period of 

 five minutes, this agitation being repeated two or three times on the 

 same day. The convention will be adopted in the following pages of 

 referring to the flasks kept at rest by the letter A, whilst those which 

 were subjected to daily agitation are distinguished by the letter B. 



The various waters were periodically examined both by plate- 

 cultivation and phenol-broth culture on the same lines as described 

 for the previous series of experiments. 



The uninfected waters yielded the following results on cheinical 

 analysis : 



2 L 2 



