CULTIVATION OF ANAEROBIC BACTERIA. 87 



tubes, may be placed in a suitable receiver and the air exhausted, or 

 hydrogen substituted for atmospheric air. Such an apparatus for 

 hydrogen has been devised by Bliicher and is shown in Fig. 57. A 

 glass dish, A, contains a smaller dish, B, which has a diameter of 

 about seven centimetres. The small dish is kept in its position in 

 the centre of the larger one by the wire ring, having three project- 

 ing arms, which is shown in the figure. The culture medium con- 

 taining the anaerobic bacteria to be cultivated is poured into the 

 small dish and the glass funnel D is put in position. This is held 

 in its place by a weight of lead which encircles the neck of the fun- 

 nel at F. A mixture of glycerin and water (twenty to twenty-five 

 per cent) is poured into the dish A to serve as a valve to shut off 

 the atmospheric air from the interior of the funnel D. Hydrogen 

 gas is introduced through the tube E, which is connected by a rub- 

 ber tube with a hydrogen apparatus. 



A somewhat similar apparatus has been devised by Botkin, in 

 which the hydrogen is admitted beneath a bell jar covering small 

 glass dishes containing the culture medium. We believe that in 

 practice the writer's method (page 83), in which Esmarch roll tubes 

 are first made, will be found more convenient than either of the last- 

 mentioned methods of preserving plates in an atmosphere of hydro- 

 gen ; or roll tubes may be prepared in the way usually practised in 

 cultivating aerobic bacteria, and these may be placed in a suitable 

 receptacle which can be filled with hydrogen. 



The addition of a reducing agent to the culture medium favors 

 the growth of anaerobic bacteria. Kitasato and Weil have recom- 

 mended formic acid or sodium formate, in the proportion of 0.3 to 0.5 

 per cent. Theobald Smith has found 0.3 to 0.5 per cent of glucose 

 to be a useful addition with the same object in view. 



