CHAPTER VI. 

 CULTIVATION OF BACTERIA; CULTURE-MEDIA. 



ACCURACY of observation requires that the bacteria be 

 separated from their natural surroundings and artificially 

 grown upon certain prepared media of standard compo- 

 sition, in such a manner that only organisms of the same 

 kind are together. 



One after another various organic and inorganic mix- 

 tures have been suggested, but, although almost any 

 compound containing organic matter, even in small 

 amounts, will suffice for the nourishment of bacteria, 

 a certain few have met with particular favor as being 

 most valuable. 



Rather than give a complete review of the work wjiich 

 has already been done, in the following pages the most 

 useful preparations only will be considered. 



Our knowledge of the biology of the bacteria has 

 shown that they grow best in a mixture containing at 

 least 80 per cent, of water, of a neutral or feebly alka- 

 line reaction, and of a composition which, for the patho- 

 genic forms at least, should approximate the juices of 

 the animal body. It might be added that transparency 

 is a very desirable quality, and that the most gener- 

 ally useful culture-media are those that can be readily 

 liquefied and solidified. 



Bouillon is one of the most useful and most simple of 

 the media. Its preparation is as follows : To 500 grams 

 of finely-chopped lean, boneless beef, 1000 c.cm. of clean 

 water are added and allowed to stand for about twelve 

 hours on ice. At the end of this time the liquor is de- 

 canted, that remaining on the meat expressed through a 

 cloth, and then, as the entire quantity is seldom regained, 



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