BACTERIA IN PUBLIC SWIMMING BATHS 
93 
Thus we see that the bacteria multiplied enormously on the first night, and 
disappeared with almost equal rapidity on the second, poisoned as it were by their own 
toxin. This extraordinary increase was mainly due to the multiplication of one bacillus, 
tor the plates examined on the second day, both morning and evening, on all occasions 
were almost a pure culture. This bacillus was found by one of us in the same baths 
two years ago, it has not been identified, its cultural characteristics are the following : — 
Agar, white opalescent growth ; Gelatine, non-liq. ; Milk, alkaline ; Glucose broth, 
decolourized ; Glycerine and Mannite broth, unchanged ; Cane Sugar broth, acid. 
Non-motile ; Gram negative. This bacillus appears also in a second class bath in the 
same building, but to a lesser extent, as the water was changed every day and 
consequently the multiplication was slight. 
Though no estimate of the multiplication rate was made in fresh water baths 
outside Liverpool, yet the fact that they contained such enormous numbers of bacteria, 
taking into consideration the capacity of the bath and the number of the bathers, proves 
that a very considerable multiplication occurred, but the predominant bacilli were not 
the same as obtained in Liverpool. 
With regard to this extraordinary multiplication in fresh water, Frank land' 11 
has pointed out that it takes place more abundantly in pure water or in water containing 
a small number of microbes to start with, than in impure or waters containing a large 
initial number. In fact, Miouel' 2 - states ' that spring water may be characterized by 
the power of rapid multiplication possessed by the bacteria present, as well as by the 
rapid decline in their numbers subsequently exhibited ' ; he found that the bacteria 
in spring water increased from a few hundred to over a million in five days, and by 
the tenth day an almost equally rat id reduction takes place. 
The water in public swimming baths fulfils these conditions, at least when it 
is clean ; the temperature being higher than that of ordinary spring and river water 
would tend to produce a more rapid multiplication. 
The important tact that multiplication of bacteria in fresh water swimming 
baths is more rapid than in salt water was confirmed in the laboratory by inoculating 
organisms derived from different sources into sterilized fresh water and salt water 
obtained from the baths.. When we consider that salt water contains bromides, iodides, 
and chlorides of sodium, and other salts, which are known to be more or less antiseptic, 
this result is not surprising. 
We have calculated in round numbers the average number of bacteria introduced 
into the water by one first class bather and one second class bather, the calculations 
being made from observations on the salt water baths in order to eliminate the error 
due to multiplication. 
Taking the average of eight observations in a first class salt water bath, which 
was emptied daily, the water contained 4,194 bacteria per c.c. at nine p.m., the 
number of bathers being 277. Making liberal allowances for the bacteria present in 
o 
