DAIRY BACTERIOLOGY 83 



Heat over boiling water or steam thirty minutes. 

 Restore weight lost by evaporation to original weight 

 for boiiillon and gelatine and twice that weight for 

 agar. Titrate and adjust reaction to the final point 

 desired. Sterihze for three consecutive days so as 

 to kill all germs present, and fill test tubes one-third 

 full. Cork with sterile cotton and sterilize again. 



Certain species of bacteria grow sufficiently well on 

 media made from beef extract instead of lean beef. 

 The former requires less work and may be used in 

 the following proportions : 



BotriLLON 



Beef extract 3 grams 



Peptone 10 grams 



Salt 5 grams 



Water 1000 c.o. 



Gelatine 



Beef extract 5 grams 



Peptone 10 grams 



Salt 5 grams 



Gelatine 100 grams 



Water 1000 c.c. 



Agar 



Beef extract 5 grams 



Peptone 10 grams 



Salt 5 grams 



Agar 20 grams 



Water 1000 c.c. 



Make potato media by washing sound potatoes and 

 cutting the ends, and with sterile cork-borer cut out 

 cylinders of the potato a little smaller than the tubes 

 to be used. Handle potato under water as much as 



