CULTURE METHODS 



31 



After inoculating the culture medium, burn over the cotton 

 stoppers and, with forceps sterilized iu the flame, push the stop- 

 pers into the test tubes for a distance of 2 or 3 cm. It is gen- 

 erally desirable to cut off part of the 

 protruding cotton before doing this. Fill 

 the space above the stopper with dry pyro- 

 galUc acid. Add with a pipette enough of 

 a 5 per cent solution of sodium hydrate 

 to dissolve the acid. Close the tubes 

 immediately with a tight-fitting rubber 

 stopper. Invert the tube if it 

 contains a sohd medium, and 

 set it aside for development. 



Fig. 17. Kipp apparatus arranged for generating hydrogen 



A, generator ; B, wash bottle containing lead nitrate solution ; C, wash bottle 

 containing silver nitrate solution 



2. Plates and miscellaneous cultures. Place the cultures in a 

 Novy jar (Fig. 16) connected with a hydrogen generator. Pass 

 the hydrogen from the Kipp generator through two wash bottles, 

 one of which contains lead nitrate solution, the other a solution 

 of sUver nitrate. It is well to add another wash bottle contain- 

 ing potassium permanganate. From time to time collect a test 

 tube full of gas from the outlet. Test by holding a burning 

 match at the mouth of the tube. As long as explosion occurs. 



