BACTERIOLOGICAL TECHNIC. 



45 



drop of a o.oi per cent, sodium nitrite solution to a four-day peptone-broth 

 culture. If a pink color appears at the end of one-half hour it indicates the 

 presence of indol. 



G. Beef Broth. — This medium is now not as extensively used as formerly. 

 It is more difficult to prepare, and shows no advantages over the bouillon 

 already described. 



Ground or Chopped Lean Beef, 500 gm. 



Peptone, 10 gm. 



Salt, 5 gm. 



Distilled Water, 1000 c.c. 



Add the water to the minced meat, shake frequently, and keep on ice for 

 twenty-four hours, then strain forcibly through cloth, or press out in a hand 



press. Add the salt to the liquid, boil, make 

 up to 1000 c.c, and add the peptone. Neu- 

 tralize, filter, and sterilize. It will be ap- 

 parent that the cold water meat infusion 

 contains merely the meat salts, meat sugar, 

 and acids, and a certain proportion of the 

 albumens. The albumens are coagulated 

 and removed in the filtering process, so that 

 nothing remains of the meat but the salts, 

 acids, and the trace of muscle sugar. Nearly 

 the whole of the meat proper is wasted. It 



Fig. 20. Fig. 21. 



Fig. 20.— Test-tube cultures, a, Stab culture. This tube is closed 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 m prepanng culture 

 media and for sterilizing test-tubes and other objects. 



is apparent, therefore, -that the meat extract bouillon answers all the pur- 

 poses of the beef broth. 

 H. Gelatin Medium. — 



Beef Extract, 3 g™- 



Gelatin; i°° g™- 



Salt, S gm. 



Peptone, 1° g"^- 



Distilled Water, io°° ^■'^ 



