LESSON I 



Preparation of Metabolic Products of Micro-organisms Heat Filtra- 

 tion Combined Heat and Filtration " Intracellular " Poisons 

 Nitrous Acid in Cholera Cultures. 



Preparation of Metabolic Products of Micro-organisms 



(a) Sterilisation by heat. 



(1) Inoculate twelve broth tubes with the Bacillus 

 pyocyaneus, and keep them at 38*5 C. for a week. 



(2) Place them in the water bath at 70 C. for ten to 

 fifteen minutes. 



(b) Sterilisation by filtration. 



(1) Inoculate several small flasks of broth (containing 

 50 cc. each) with the Bacillus pyocyaneus, and keep them 

 at 38-5 C. for a week. 



(2) Filter the broth cultures through a sterile Berkefeld 

 filter into a sterile flask. 



(c) Combined sterilisation by heat and filtration. 



(1) Inoculate several small flasks of broth (containing 

 50 cc. each) with the Bacillus pyocyaneus, and keep them 

 at 38-5 C. for a week. 



