152 THOMPSON YATES LABORATORIES REPORT 
These constituents are heated together until the solids are dissolved and then filtered. 
After filtration, sufficient neutral litmus solution to give a distinct colour is added. 
The medium is then distributed into test tubes, and one of Durham's fermentation 
tubes placed in each. Sterilization is effected in twenty minutes by Koch's 
sterilizer on each of three successive days. After the third sterilization the small 
inner tube should be quite full. Glucose was used instead of lactose in order not 
to exclude the B. enteritidis of Gaertner and allied organisms, as they are incapable 
of fermenting lactose. 
The percentage of glucose was determined by careful experiments, which led 
to the conclusion that any higher percentage was detrimental to the growth of the 
B.C.C. and allied organisms. 
The absence of sodium chloride and the extractives of meat enables the 
medium to be of an almost uniform composition, of which the advantage is obvious. 
The temperature of incubation is 42° C, the same as that for the agar medium ; this 
enables the reaction to occur quickly and favours the growth of all intestinal 
organisms. The litmus indicates at once whether there is acid formation. The 
Durham's tube shows whether there is fermentation of the glucose. 
The taurocholate favours the growth of the group of organisms which are 
the most important from the point of view of faecal contamination, viz., the B.C.C. 
and Gaertner groups, etc. 
Characteristic reaction 
On inoculating- this medium with B.C.C. or the Gaertner bacillus, the 
following characteristic reaction is produced within forty-eight hours. The appended 
drawings show it clearly. 
The medium is uniformly red in colour. The fermentation tube is filled with gas, 
and the surface of the medium is covered over with a mesh work of bubbles, whilst 
a constant stream of bubbles can be seen rising to the surface. After inoculation 
with B.T.A., the medium becomes uniformly red in colour, but there is no production 
of gas as the bacillus is incapable of fermenting glucose. 
