518 



PATHOGENIC MICllOORGANISMS 



tail the different methods devised for this purpose. The one de- 

 scribed below is the one most frequently employed, and is both simple 

 and reliable. 



Cultures are taken from throats upon Loeffler's blood serum. 

 These are permitted to grow at 37.5° C. for from eighteen to twenty- 

 four hours. At the end of this time about 5 c.c. of bouillon are 

 poured into the tubes and the growth is gently emulsified in the broth 

 with a platinum loop. Two or three loopfuls of this emulsion are 

 then streaked over the surface of glucose agar, serum agar, or nutrose 



Wil^vTw.rv-^s^- - ."-- .^T— »; 





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. V 









•; .%■■■% 





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tf j^^^i!^.^.. 



Fig. 106. — Colonies op Bacillus diphtheri^e on Glycerin Agar. 



agar. After twenty -four hours' incubation these plates show char- 

 acteristic colonies which can be easily fished and again transferred 

 to LoefHer tubes or any other suitable medium. The same method 



