66 METHODS OF CULTIVATION OF BACTERIA 



treated, the free end of one of the rubber tubes is pushed over it 

 till the glass of the U-tube is in contact with the glass of the 

 culture tube. In the dry tube 1 or 2 grammes of pyrogallic 

 acid are placed, and the powder is packed down with a layer of 

 filter paper. Ten or twenty cubic centimetres of a 10 per cent, 

 solution of sodium hydrate are then poured in, and the tube is 

 quickly connected up by the rubber tubing with the other end 

 of the U-tube. In this apparatus the oxygen is absorbed by the 

 sodium pyrogallate, and the conditions for anaerobic growth 

 are fulfilled. 



Buchner's Anaerobic Tube. This may be used either for 

 maintaining surface growths of anaerobes or for keeping free 

 from oxygen sloped culture media which are being used for 

 separating anaerobes from mixtures. Dry pyrogallol is placed 

 in a cylindrical jar of diameter sufficient to contain the tube 

 or tubes of media. The tubes are v then inserted, potassium 

 hydrate solution (p. 65) is poured into the jar, and its mouth 

 quickly stoppered with a rubber or glass stopper. The stopper 

 is made airtight by sealing with paraffin. The pyrogallol 

 absorbs the oxygen in the jar, and thus the cultures are kept in 

 oxygen-free surroundings. 



Growth in Tubes with Pyrogallol-saturated Plug. Sloped 

 cultures can be maintained oxygen-free as follows : The medium 

 is placed in a long test-tube and inoculated. The plug of the 

 tube (which ought to be rather tight) is pushed down into the 

 tube, and a little dry pyrogallol placed on the top of it. A few 

 drops of the potassium hydrate solution are dropped on the 

 crystals, and a second plug is inserted in the mouth of the tube. 

 This is pushed home, and melted paraffin run on to the top to 

 prevent access of outside air. 



Cultures of Anaerobes in Liquid Media. It is necessary to 

 employ such in order to obtain the toxic products of the growth 

 of anaerobes. Glucose broth is most convenient. It is placed 

 either (1) in a conical flask with a lateral opening and a per- 

 forated indiarubber stopper, through which a bent glass tube 

 passes, as in Fig. 24, a, by which hydrogen may be delivered,. 

 or (2) in a conical flask with a rubber stopper furnished with 

 two holes, as in Fig. 24, b, through a tube in one of which 

 hydrogen is delivered, while through the tube in the other the 

 gas escapes. The inner end of the gas delivery tube must in 

 either case be below the surface of the liquid ; the inner end of 

 the lateral nozzle in the one case, and the inner end of the 

 escape tube in the other, must of course be above the surface of 

 the liquid. The single tube in the one case and the two tubes 



