Report on the Bacteriology of Water. 



519 



EXPERIMENTS ON THE RELATIVE LONGEVITY OP THE TYPHOID BACILLUS IN 

 UNSTERILISED THAMES WATER AND IN STEAM-STERILISED THAMES 

 WATER REINOCCLATED WITH THAMES WATER BACTERIA. (11.1.1894.) 



In this series of experiments one portion of a, sample of Thames 

 water collected at Hampton on January 9th, 1894, was infected with 

 typhoid in the natural unsterile condition, a second portion was 

 similarly infected after having been previously sterilised by steaming, 

 and a portion of the latter was again supplied with the Thames water 

 bacteria by inoculating it with a few drops of the same unsterilised 

 Thames water. 



Infection of the Waters. I have found in the previous series of ex- 

 periments that, in taking the surface-growth from a well-matured 

 typhoid culture, a large proportion of the bacilli are dead, whilst 

 even those which are alive are often in a more or less weakened 

 state. On this account I now generally prefer to take the bacilli for 

 experiments such as these directly from fresh plate cultivations, 

 selecting the largest and most vigorous looking colonies. 



In the present series of experiments a gelatine plate culture (five 

 days old) of the typhoid bacillus was employed ; fifty-seven surface 

 colonies were carefully removed by means of a sterile platinum loop and 

 transferred to 50 c.c. of steam-sterilised Thames water in a small 

 sterile-stoppered bottle ; this was then violently shaken for fifteen 

 minutes as usual, measured quantities of this liquid being then used 

 for the infection of the large volumes of water. Thus, 800 c.c. of 

 steam-sterilised Thames water were infected with 8 c.c. of the above 

 liquid, 400 c.c. of this was kept, and will be referred to in the follow- 

 ing experiments as 



" Typhoid-infected Steam-sterilised Thames Water." 



To the remaining 400 c.c. was added 1 c.c. of the unsterilised 

 Thames water, with the object of imparting to it the several kinds of 

 water bacteria in Thames water. This portion will be referred to in 

 the following experiments as 



" Typhoid-infected Steam-sterilised Thames Water inoculated with a 

 feiv drops of Unsterile Thames Water." 



Again, 400 c.c. of unsterilised Thames water were inoculated with 

 4 c.c. of the water attenuation of typhoid mentioned above, and this 

 will be referred to in the following pages as 



" Typhoid-infected Unsterilised Thames Water" 



These several infected waters, as well as some of the uninfected 

 unsterilised Thames water, were placed in sterile flasks covered with 



