72 PHARMACEUTICAL BACTERIOLOGY 



E. Peptone Solution. The medium is employed to test for the develop- 

 ment of indol by certain bacteria. It consists of 



Peptone, 10 gm. 



Salt, / 5 g m - 



Distilled Water, 1000 cc. 



Boil, filter, and sterilize as for bouillon. The bacteriological indol lest 

 is of great importance in medical practice, and the chances are that physi- 

 cians will require this medium. However, sugar-free beef broth is also 

 used for this test; in fact, it is generally preferred. Beef contains a small 

 amount of muscle sugar, which must first be removed. 



FIG. 20. FIG. 21. 



FIG. 20. Test-tube cultures, a, Stab culture. Thifc tube isfclosed with a rubber 

 stopper to prevent drying of medium; b, streak or smear culture on slant, tube closed 

 with rubber cap. (Williams.) 



FIG. 21. The ordinary rice cooker. A most valuable apparatus in preparing cul- 

 ture media and for sterilizing test-tubes and other objects. 



F. Sugar-free Bouillon. Grind the fat-free beef through a meat 

 grinder; add water, and inoculate at once with a pure culture of Bacillus 

 coli communis, and allow to incubate for twelve to fifteen hours at 38 C., 

 then boil, filter, add peptone and salt, and prepare like bouillon; or, 

 inoculate nutrient bouillon with the colon bacillus and prepare as above. 

 However, before using the medium it should be tested for indol, as it has 

 been proved that B. coli communis may form indol in beef extract. The 

 indol test in bacterial cultures is made by adding two drops of concentrated 



