ANAEROBIC CULTIVATION V\ 



been poured. By means of a thistle funnel, an equal 

 volume of 20 per cent, caustic potash 1 or soda solution 

 is then added. As quickly as possible the thistle funnel 

 is withdrawn without mixing the solutions, and the stopper, 

 well vaselined, inserted and twisted well home, and some 

 melted paraffin may be poured all round the joint and 

 melted in with a hot iron. The solutions in the bottle are 

 now well mixed, and the whole is placed in a suitable 

 incubator. The Buchner's tube (Fig. 11) is convenient 

 for single test-tube cultures. It consists of a strong glass 

 test-tube, large enough to take an ordinary test-tube, and 

 having a constriction about an inch and a half from the 

 bottom. The constriction supports the test-tube culture, 

 while the mixture of pyrogallic acid and .caustic potash 

 fills the portion below the constriction. A well-fitting 

 rubber cork closes the mouth of the tube, and the joint 

 may be paraffined for additional security. If a Buchner's 

 tube is not available, the cotton- wool plug of the culture 

 tube may be pushed into the tube for an inch, some solid 

 pyrogallol is placed on the wool plug, this is just moistened 

 with caustic potash solution and the tube is stoppered 

 with a rubber cork. 



The displacement of the atmosphere by means of 

 hydrogen may be adopted, and is to be preferred for fluid 

 cultures. Hydrogen does not seem to inhibit the growth 

 of any anaerobic organisms, whereas carbon dioxide gas, 

 which might be still more conveniently used, has a very 

 decided inhibitory action on some species. The hydrogen 

 is best generated from zinc and sulphuric acid in a Kipp 

 apparatus, or the compressed gas in cylinders, or even 

 coal-gas, may be used. Care must be taken that all 



1 Thirty-two grm. of pyrogallic acid and 64 grin, of caustic potash 

 dissolved in 100 c.c. of water will absorb 9200 c.c. of oxygen. At the 

 same time some carbon monoxide is evolved (122-5 c.c.). The evolu- 

 tion of CO is a minimum when the potash is in excess and only one- 

 lifth or the theoretical absorbable amount of is absorbed. 



