84 



EXPERIMENTAL DAIRY BACTERIOLOGY 



perforation in which is placed a glass tube carrying a ground- 

 glass stopcock. The stopcock should be lubricated with vase- 

 line or, preferably, a saturated solution of rubber in paraffin. 

 The rubber stopper should be coated with soft paraffin so 



r, that it will not adhere to the glass. 



/ k Just before closing the bottle a small amount 



of a 10 per cent solution of potassium hydrate 



is added. The cock in the tube leading to the 

 generator is closed, and the air is exhausted 

 from the vessel. The cock between the pump 

 and the Y-tube is then closed, while the one 

 admitting the hydrogen is gradually opened. 

 When the jar is filled with hydrogen the ex- 

 haustion is repeated. The process must be 

 repeated five or six times. Any slight amount 

 of oxygen remaining will be absorbed by the 

 pyrogallic acid. In order to avoid the forcing 

 of the stopper from the jar, due to the expan- 

 sion of the hydrogen in the incubator, a nega- 

 tive pressure of 100150 mm. of mercury 

 should be obtained by partially exhausting 

 the vessel. 



Other more simple but less satisfactory 

 methods of obtaining anaerobic conditions 



FIG 16 BURRI'S w ^ ^ e f un d described in text-books on 

 CULTURE TUBE general bacteriology. 



This tube allows The medium employed for anaerobic cul- 



without the use of Dextrose is usually employed. 



In order to avoid the trouble connected 

 with the use of Petri dishes in anaerobic work, the method 

 devised by Burri is recommended for the isolation of pure 



