Water for Bacteriological Analysis. 27 
bacteria can go on, and the ice could be replenished by the 
officials from time to time, while the padlock or a seal 
would prevent its being tampered with. The space occu- 
pied by this box (18’’x11’’x8’’) admits of its being 
placed in a large hot-air sterilizer and heated together with 
its contents to 150° C. A small piece of fine string placed 
in the neck of each bottle permitted the escape of any mois- 
ture, so that it is unnecessary to dry the bottles thoroughly 
before heating them. As the box is quite dust-tight the 
necks of the bottles remain sterile until the time comes 
to use them, doing away entirely with the employment of 
rubber caps. 
In some cases when it seemed of interest to examine 
great stretches of water [ took my samples from off the bow 
of a passenger steamboat in a very simple manner. By 
using a stout fishing rod and about twelve feet of line a 
sample can be secured well outside the ‘“ wash ”’ of the boat, 
even at a speed of 12 to 15 miles per hour. To ensure the 
bottle sinking I wrapped a piece of sheet lead round it. By 
making the cast well ahead the bottle usually sank 6 to 8 
feet. 
As these examinations were always made in duplicate 
the accidental encounter of any extraneous source of pollu- 
tion would infallibly have been shown by an abnomal 
excess of growth in one of the two samples. A striking 
proof of the delicacy of the method is that the duplicate 
samples always gave practically the same number of 
colonies. This “fishing” was often found a convenient 
method of obtaining a sample from the banks of a stream. 
To ensure the accuracy of the result in estimating the 
number of bacteria in a water it is of great importance to 
curtail to a minimum the time which elapses between the 
collection of the sample and the plating of the cultures, to 
guard against a possible increase of bacteria in the interval. 
It is also advisable to make the cultures in some fiat vessel 
which permits of their being counted from time to time 
without exposing the gelatine to the danger of receiving 
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