92 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
About mid-day about half-a-pint of bath water, already contaminated by 
numerous bathers, was collected in a sterile bottle, and a small quantity of this was 
poured into a sterile test-tube. 
The bottle (with the remaining 90 c.c.) having been tightly corked with a 
sterile glass stopper, was sunk to the bottom of the bath, and left there until nine 
p.m. 
By immediately plating a sample of the water in the test-tube, the number 
of bacteria present in a cubic centimetre of the water in the bottle at mid-day was 
found. It is clear, as the bottle was sunk in the bath, that the organisms in it 
were subjected to the same conditions of light and temperature as the rest of the 
organisms in the bath. If the organisms introduced into the bath before noon 
multiplied by nine p.m., then the organisms in the bottle would also multiply, and 
the rate of multiplication could be calculated. A sample from the bottle was taken at 
nine p.m.,, and the number of bacteria per c.c. was ascertained. The number of bacteria 
in the bath water itself on that particular night was also found. 
These observations were repeated on rive different occasions, and gave the 
following average result : — 
Water in the bottle at mid-day — 921 bacteria per c.c. 
„ „ nine p.m.— 1,336 „ „ „ 
„ bath „ —5,027 „ „ „ 
On two occasions when the water in a second-class salt water bath was not 
changed on Sunday owing to the small number of bathers, the bacteria averaged 
380 per c.c. on Sunday at nine a.m., and 1,270 per c.c. on Monday at nine a.m. 
Lastly, the fact that in the month of October, when there are few bathers, the number 
of bacteria reached, in a series of five observations, only 966 per c.c, is additional 
evidence that multiplication takes place very slowly in salt water. 
The bottle observations were repeated in a second class tresh water bath on six 
occasions, with the following average results : — 
Water in the bottle at one p.m. — 5,772 per c.c. 
„ „ „ nine p.m.— 34,315 „ 
„ „ bath „ — 87,000 „ 
thus in the same time and under the same conditions, the bacteria in the salt water 
bath scarcely multiplied at all, while those in the fresh water bath increased six-fold. 
For some unascertained reason an extraordinarily rapid multiplication of bacteria 
was liable to occur in a fresh water bath which was frequently examined, when the 
water was two or three days' old. By special arrangement the water was left in this bath, 
which was very little used, for three days in succession without changing. The number 
of bacteria were estimated night and morning on each of the three days. 
This series of observations was made on two occasions. By adding together 
the number present on each day in the morning and evening, and striking an average, 
there were : — First day, 1,983 ; second day, 72,625 ; third day, 17,770. 
