280 BACTERIA PATHOGENIC TO MAN 



gas-bubbles through the medium, clear streaks ramify through the 

 otherwise diffusely cloudy tube contents. This characteristic appear- 

 ance is not produced when the medium is incorrect in reaction or in 

 consistency. With untried media it is always well to insert a platinum 

 wire into the tube contents and stir them 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 inocu- 

 lated from them, and the growth in the tubes allowed to develop for 

 about eighteen hours at 37 C. If these tubes then present the charac- 

 teristic 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 organ- 

 isms isolated in this manner have been subjected to the usual tests for 

 the recognition of the bacillus typhosus, and have always corresponded 

 in all their reactions to those given by the typical typhoid bacillus. 



THE CAPALDI PLATE MEDIUM. In his original paper, Capaldi 

 gives the following recipe: 



Aquadest. 1000 



Gelatin 20 



Mannite (grape-sugar) . . . . . . 10 



Sodium chloride 5 



Potassium chloride ....... 5 



Boil, filter, add 2 per cent, agar and 10 c.c. of normal sodic hydrate solution ; boil, 

 filter, and sterilize. 



In making up the medium for work the only variation was that in 

 the original recipe the agar was added when the gelatin was put in, and 

 the gelatin was added after the first filtration. 



The Capaldi medium is usually employed for surface cultures, but 

 can be inoculated while melted in the tubes. Plates may be made 

 beforehand, so that they are ready for use when the specimen comes 

 in. As these plates are to be kept at 37 C., the difficulties in regard 

 to temperature are avoided; but, unlike the Eisner plates, other organ- 

 isms besides the colon and typhoid develop and may cause some con- 

 fusion. In making the plates one or two are inoculated by gently carry- 

 ing across their surface a platinum loop of feces or urine. Others are 



