66 METHODS OF CULTIVATION OF BACTEKIA 



methods separate colonies have been obtained, growth may be 

 maintained on media in contact with ordinary air. The media 

 generally used are those which contain reducing agents, and the 

 test-tubes containing the medium must be filled to a depth of 

 4 inches. They are sterilised as usual, and are called " deep " 

 tubes (Fig. 12, c). The long straight platinum wire is used for 

 inoculating, and it is plunged well down into the " deep " tube. 

 A little air gets into the upper part of the needle track, and no 

 growth takes place there, but in the lower part of the needle 

 track growth occurs. From such " deep " cultures growths may 

 be maintained indefinitely by successive sub-cultures in similar 

 tubes. Even ordinary gelatin and agar can be used in the same 

 way if the medium is heated to boiling-point before use to expel 

 any absorbed oxygen. 



Carroll's Method for Anaerobic Gultwes. — This may be used 

 with culture tubes containing any of the media suitable for 

 anaerobes and also for surface growths on sloped tubes. There 

 are required a dry tube of the same diameter as the culture tube, 

 a short U-shaped glass tube, and two pieces of rubber tubing 

 all of like diameter. The culture tube having been inoculated, 

 the plug is pushed home below the lip of the tube. The ends 

 of the U-tube are smeared with vaseline and a rubber tube 

 slipped over each ; the end of the culture tube being similarly 

 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 grms. 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 

 quiekly 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 then inserted, potassium 

 hydrate solution (p. 62) 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. 



