214 Transactions of the Society. 



Delepine and Dr. Thresh, both of whom continued their allegiance 

 to bleaching powder as a powerful bactericidal and disinfecting 

 agent. In the meantime, in Massachusetts and other centres in 

 the United States, numerous experiments were being tried, and the 

 results obtained fully bore out what had already been observed in 

 this country, both sewage and water of all types and qualities 

 being sterilized by means of the addition of comparatively small 

 quantities of bleaching powder. 



For many years I have made bacterioscopic examinations of 

 the Cambridge water, and, from time to time, have carried on 

 small sterilizing experiments, as a result of which, as already stated, 

 I early satisfied myself that ozone and chloride of lime were 

 the only two substances at present available for the rapid and 

 effective treatment of drinking-water. The production of ozone 

 was, however, as already noted, an elaborate and somewhat costly 

 process, whilst chloride of lime, though cheap and easily applied, 

 in the proportions used and left unneutralized, usually gave a 

 markedly unpleasant taste to the treated water ; whilst, as the result 

 of neutralization with thio-sulphate of soda, a very flat and insipid 

 flavour was imparted to the water. Further, as a considerable 

 number of organisms were found in the thio-sulphate solution, 

 many of our cultivation experiments were rendered valueless ; and 

 although most of such organisms were derived from the unsterilized 

 water used in making up the solution, it was evident that the thio- 

 sulphate had little bactericidal action on any of the organisms present. 

 Moreover, it seemed to me to be unnecessary to complicate the 

 process ; rather should it be simplified in every way possible, and I 

 set out to find whether even smaller quantities of chloride of lime 

 than any yet used were not effective. Ultimately I was delighted 

 to find that although it is difficult to destroy the spore-bearing 

 organisms met with in water, and even some of the ordinary sapro- 

 phytic water organisms, it is a comparatively easy matter to kill 

 off what one may classify as the non-spore-bearing micro-organisms 

 whose usual habitat is the intestinal canal. I therefore concentrated 

 my efforts on this type of non-spore-bearing organism. Using the 

 amounts of chloride of lime that had been used by the American 

 investigators and by Dr. Thresh, I found, as did they, that the 

 presence of organic matter in solution and even particulate matter 

 in the water, along with Bacillus coli communis, invariably led to 

 a diminution of the bactericidal activity of the chloride of lime 

 solution. The results obtained were always less satisfactory than 

 when the B. c. c. alone was present, even in considerable numbers, 

 i.e. when the water contained little organic matter in solution, 

 and when coarse suspended matter had been filtered from the 

 water. Working with pure chalk water in which were but few 

 c f tb». B. c. c, I found that not only this organism but the other 



