28 BACTERIOLOGY 



Bouillon 



In looo cc. of distilled water dissolve in the cold, Witte's 

 peptone, lo g. ; common salt, 5 g. ; and 5 g. of Lie- 

 big's extract of beef. When the ingredients are in solution, 

 titrate, using phenolphthalein as an indicator. Make neutral to 

 phenolphthalein with sodium hydrate. Boil for 15 minutes, 

 using a rose burner so that the ilame does not impinge against 

 the bottom of the dish ; restore to the original volume 1000 cc. ; 

 titrate with phenolphthalein ; adjust reaction to the final point 

 desired ; boil 5 minutes ; restore to original volume ; filter, tube, 

 and sterihze. 



Nutrient Gelatin 



In 1000 cc. of distilled water dissolve the ingredients used for 

 bouillon. When the ingredients are in solution, add 100 g. of 

 the best sheet gelatin, and warm until the latter is completely dis- 

 solved. Titrate ; make neutral to phenolphthalein with sodium 

 hydrate. Add the beaten whites of two eggs, and boil for 15 

 minutes with frequent -stirring, when the medium should be 

 perfectly clear. Restore to original volume; titrate; adjust 

 reaction to final point desired. Boil for 5 minutes ; restore to 

 original volume ; filter, tube, and sterilize. 



Nutrient Agar 



Boil 15 g. of shred agar in 500 cc. of distilled water 

 for half an hour, or until the agar is completely dissolved ; 

 restore to original volume, cool and solidify. This constitutes 

 the so-called agar jelly. In 500 cc. of distilled water dis- 

 solve 10 g. of Witte's peptone, 5 g. of common salt, and 5 g. 

 of Liebig's extract. When ingredients are in solution, titrate, 

 and make neutral to phenolphthalein with sodium hydrate. Add 

 the 500 cc. of agar jelly previously prepared, breaking the lat- 

 ter into small fragments. Boil for 5 minutes to dissolve the agar; 

 cool to 65° C. Add the beaten whites of two eggs ; boil for 



