BACILLUS TTPHOSUS. 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. 

 The organisms isolated in this manner have been sub- 



28 



