44 CULTIVATION OF BACTERIA. 



next day for half an hour. To prevent the potatoes from 

 turning dark, Abbott advises that the cut cylinders be allowed 

 to stand in running water for twenty-four hours. Before 

 sterilizing, it is well to place a few drops of sterile water in 

 each tube to keep the potatoes moist. 



Potato-juice : This is made as follows : Add 100 grams of 

 grated potato to 300 c.c. of water and place on ice over night. 

 Express the juice through a cloth and cook for one hour on a 

 water-bath. Filter and add 4 per cent, of glycerin. Trans- 

 fer to tubes and sterilize the same as bouillon. This is said 

 to be an excellent medium for the tubercle bacillus. 



The phosphorescent bacteria grow best in a medium con- 

 taining 2 or 3 per cent, of sodium chloride. The addition 

 of 3 or 4 per cent, of potassium nitrate will demonstrate the 

 reducing power of the nitrifying bacteria. 



Urine can be used as a culture-medium, especially for the 

 gonococcus and the Micrococcus urece. 



Fresh eggs, raw or boiled, whites of eggs, the yelk, bread 

 paste, hydrocele fluid, ascitic fluid, aqueous humor, and many 

 other substances and preparations, have been used as culture- 

 media. 



