62 ESSENTIALS OF BACTERIOLOGY 



for ten seconds (over flame) ; bleach with glycerin and ether 

 (equal parts); rinse in water, alcohol, dry, and mount. 



CHAPTER DC 

 CULTIVATION OF BACTERIA 



Artificial Cultivation. The objects of cultivation are to 

 obtain germs in pure culture, free from all foreign matter, 

 isolated, and so developed as to be readily used either for 

 microscopic examination or animal experimentation. 



To develop bacteria properly we supply, as nearly as possi- 

 ble, the conditions which hold for the especial germ in nature. 

 With the aid of solid nutrient media the bacteria can be easily 

 separated, and the methods have been gradually evolved 

 from those originally devised by Pasteur and Koch. 



Sterilization of Culture-media, etc. If we place our 

 nutrient material in vessels that have not been properly dis- 

 infected, we will obtain growths of bacteria without having 

 sown any. 



If we have thoroughly cleaned our utensils and then not 

 taken care to protect them from further exposure, the germs 

 we have sown will be effaced or contaminated by multitudes 

 of others that are constantly about us. We, therefore, have 

 two necessary precautions to take: 



First, thoroughly to clean and sterilize every object that enters 

 into, or in any way comes in contact with, the culture. 



Second, to maintain this degree of sterility throughout the 

 whole course of the growth, and prevent, by proper containers, 

 the entrance of foreign germs. 



Disinfectants. Corrosive sublimate (bichlorid of mercury), 

 which is the most effective agent we possess, cannot be gener- 

 ally used because it renders the soil unproductive, and, there- 

 fore, must be employed only in washing dishes, to destroy the 



