CULTIVATION OF ANAEROBIC BACTERIA 65 



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Another plan is to pour into the tube two or three centi- 

 metres of melted agar at a temperature not higher than 40 C. 



After inoculation plug the tube and cover the opening with a 

 tight-fitting rubber cap washed in a dilute solution 

 of mercuric chloride. 



Or the tube may be placed in a Buchner tube, 

 described below, without the rubber cap. 



Under these conditions most anaerobic 

 organisms readily form colonies in the lower part 

 of the medium. 



(2) Growth of Anaerobes in a Buchner Tube. 

 This is the most generally adopted method. 



The Buchner tube consists of a strong wide- 

 bored test-tube, near the base of which is a 

 constriction (Fig. 25). 



Make a streak of the organism to be grown 

 on an agar or gelatine slant or potato-slice. 



Then take i to 2 grams of pyrogallic acid and 

 dissolve it in 2 to 3 c.c. of water; to this add 10 

 to 15 c.c. of a 20 per cent, solution of caustic 

 potash. 



Pour the mixture into the Buchner tube and 

 also place the test-tube containing the bacteria 

 inside it as soon as possible. 



Plug the opening of the Buchner tube im- 

 mediately with a close-fitting rubber stopper, 

 slightly greased with vaseline : to make the 

 joint gas tight it is advisable to cover it with 



J f X. 



melted paraffin Wax. 



The mixture of pyrogallic acid and caustic 

 potash absorbs the oxygen in the tube, leaving s amsms - 

 only the nitrogen of the air with a small trace of carbon monoxide 

 which is produced from the mixture. In this atmosphere most 

 anaerobic organisms grow satisfactorily. 



(3) In Yeast Flask in Hydrogen or other Inert Gas. 





FIG. 25. Buchner 

 tube, arranged 



