BILE SALT BROTH 
Time of incubation 
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In order to make the test as rapid as possible, it was, at the outset, necessary 
to determine some limit for the time of incubation. This we have fixed at forty- 
eight hours, as we are satisfied, from numerous experiments, that if B.C.C., etc., be 
present, the reaction occurs within this limit. In the majority of cases, it is within 
twenty-four hours. 
Precautions to be observed when using the test 
1. Formation of Gas. Frequently a few small bubbles collect in the upper 
part of the fermentation tube after incubation. This is apparently due to evaporation 
of liquid from the tube owing to the high temperature, and can readily be recognized. 
It is totally different in appearance to the fermentation caused by the reacting 
organisms, which is general : the whole liquid being permeated with rising bubbles 
of gas, and the surface covered with a meshwork of the same. 
2. Pipettes. It is advisable to use a separate pipette for making each dilution, 
and for inoculating the tubes ; but if this be impracticable, one pipette should be 
used for making the dilution, and a second for inoculating the tubes, care being taken 
to commence the inoculation at the highest dilution. 
o 
3. Plates. When it is desired to make plate cultivations from the Taurocholate 
broth, this should be done forty-eight hours after inoculation, as the development of 
acid tends to kill off the organisms. 
We have examined the behaviour in this medium of ninety-four organisms, 
most of which were obtained from Krai's laboratory. 
Grouping of organisms 
Four headings obviously present themselves under which the organisms can 
be grouped : — 
L Those producing acid and gas. 
II. Those producing acid only and no gas. 
III. Those capable of growth in the medium, but producing neither acid 
nor gas. 
IV. Those incapable of growth in the medium, 
and finally a fifth group : 
V. Those incapable of growth on any medium at the temperature of 
incubation, viz., 42 0 C. 
Division I contains seventeen organisms : — 
1. B. coli communis (Escherich) (subculture of original strain) 
2. B. acidi lactici (Hueppe) 
3. B. cavicida (Brieger) 
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