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60
this work in the country. I therefore decided to send test
samples to another laboratory.
Two churns of milk were selected upon delivery at each
of two hospitals in Hammersmith and duplicate samples
taken from each. The same methods were adopted for each
sample. Bottles, sterilized under exactly similar conditions
in the laboratory, were used for each of the samples. They
were immediately packed on ice and four were submitted
to the usual laboratory and four to another well-known
institution.
Sample "A" was reported by one laboratory to contain
39,850 bacteria per c.c. (well within the prescribed limit)
and by the other 144,000 per c.c. (nearly 50 per cent. above
the legal maximum). The other three reports all showed
similar variation.
In July I had further tests made with startling results.
A quart bottle of pasteurised milk was taken and, after being
thoroughly shaken, divided into six parts. Sterile bottles
were used and every precaution taken during the division.
Two of these bottles were submitted to each of three laboratories.
The following table gives particulars of the reports
received :—
No. of
sample Temp. No. of Presence of B. Coli (24 hrs.)
„ Bacteriologist on bacteria
Sample arrival per c.c. 1/10 1/100 1/1,000 1/10,000
1 No. 1 Laboratory 13˚'C 9,270 +- - -
2 No. 1 „ 13°C 14,300 +- - -
3 No. 2 „ ll'C 147,333 - - -
4 No. 2 „ 11˚0 3,400,000 - -
6 No. 3 „ 14˚0 36,000 +- - -
6 No. 3 „ 14*0 47,000 +- - -
It will be seen that one report gives a bacterial count of
9,270 per c.c. and another 3,400,000 per c.c. for the same
milk and that the results obtained by one laboratory vary
from 147,000 to 3.400,000.
Other tests have been made and the above figures are
typical of the results obtained.