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BACTERIOLOGICAL LABORATORY TECHNIC 



O 



pipette drops of this highly attenuated mixture are dropped into 

 flasks of sterilized bouillon or wort. Among a great number of 

 flasks so inoculated, some will be found sterile, others will contain 

 two or three different forms of bacteria, while a few will, perhaps, 

 contain a pure colony of the kind of bacteria for which a search is 

 being made. 



Another method is to inject some matter con- 

 taining pathogenic bacteria into a rabbit or 

 guinea pig. The various juices and the leuco- 

 cytes of the animal destroy the non-pathogenic 

 bacteria and a pure culture, often of a pathogenic 

 form, may be isolated from the blood or miliary 

 abscess or tubercle of the animal at autopsy and 

 transferred to culture media. 



By far the most useful and ingenious method 

 of procedure is the Koch, or plate method. This 

 is used in many laboratories all over the world. 



Koch was the first to employ solid culture media 

 for this purpose, and his method depends upon 

 the principle that a liquid culture media may be 

 inoculated with bacteria and then spread out on 

 sterile glass plates or dishes where it quickly 

 hardens, the bacteria being uniformly separated 

 from each other, and for a time at least kept 

 isolated by means of the solid media, and after 

 F IG> ^ If Needles they have developed into isolated colonies they 



used for inoculating may fe transplanted to tubes, of media in which 

 media. 



they may be stored. In another way it a man 



wanted to secure a pure lot of seed of a single variety from a multi- 

 tude of many kinds, it would perhaps be impossible to pick out by 

 hand the seed wanted because of their fewness and smallness, but 

 if he sowed them and waited until the plants developed they could 

 then be identified and gathered (Abbott). Thus it is with plate 

 cultures. 



