BACILLUS TYPHOSUS, 433 
where they were inoculated by the platinum needle. 
Others grow diffusely through the medium, but owing 
to the production of gas and the passage of gas-bubbles 
through the medium, clear streaks ramify through the 
otherwise diffusely cloudy tube contents. This charac- 
teristic appearance is not produced when the medium 
is incorrect in reaction or in consistency. With un- 
tried media it is always well to insert a platinum wire 
into the tube contents and stir it about ; if any gas is 
liberated the culture is not one of the typhoid bacillus 
and the medium is not correct. 
Method of Making the Test. The usual method of 
making the test is to take enough of the specimen of 
feces or urine—i. e., from one to several loops—and 
transfer it to a tube containing broth. From this 
emulsion in broth five or six plates are generally 
made by transferring one to five loops of the emulsion 
to tubes containing the melted plate medium and then 
pouring the contents of these tubes into Petri dishes. 
These dishes are placed in the incubator at 37° C. 
and allowed to remain for eighteen to twenty-four 
hours, when they may be examined. If typical 
thread-forming colonies are found the tube medium 
is inoculated from them and the growth in the tubes 
allowed to develop for about eighteen hours at 37° C. 
If these tubes then present the characteristic clouding, 
experience indicates that the diagnosis of typhoid may 
be safely made, for the typhoid bacillus alone, of all 
the organisms investigated, has displayed the power 
of giving rise both to the thread-forming colonies in 
the plating medium and the uniform clouding in the 
tube medium when exposed to a temperature of 37° C, 
Fhe organisms isolated in this manner have been sub- 
28 
