64 METHODS OF CULTIVATION OF BACTERIA 



containing anaerobes. 



test-tube and the stopper and round the .perforations for the gas- 



supply tubes, to ensure that the apparatus is airtight. The 



gelatin is thus in an atmosphere of hydrogen in which the 

 colonies may develop. The latter may 

 be examined and isolated in a way 

 which will be presently described. The 

 method is admirably suited for all 

 anaerobes which grow at the ordinary 

 temperature. 



(b) Bulloch's Apparatus for An- 

 aerobic Culture. This can be recom- 

 mended for plating out mixtures 

 containing anaerobes, and for obtaining 

 growths (especially surface growths) of 

 the latter. It consists (Fig. 23) of a 

 glass plate as base on which a bell 

 jar can be firmly luted down with 

 unguentum resina, In the upper part 

 of the bell jar are two apertures fur- 

 nished with ground stoppers, and 



through each of the latter passes a glass tube on which is a 



stop-cock. One tube, bent slightly just after passing through 



the stopper, extends nearly to the bottom of the chamber; 



the other terminates immediately 



below the stopper. In using the 



apparatus there is set on the 



base -plate a shallow dish, of 



slightly less diameter than that 



of the bell jar, and having a little 



heap of from 2 to 4 grammes of 



dry pyrogallic acid placed in it 



towards one side. Culture plates 



made in the usual way can be 



stacked on a frame of glass rod's 



resting on the edges of the dish, 



or a beaker containing culture 



tubes can be placed in it. The 



bell jar is then placed in position 



so that the longer glass tube is 



situated over that part of the 



bottom of the shallow dish far- 



thest away from the pyrogallic 



acid, and the bottom and stoppers are luted. The air in the 



bell jar is now expelled by passing a current of hydrogen through 



. 23 .-BullocVs apparatus for 

 anaerobic plate cultures. 



