METHODS USED IN CULTIVATION OF BACTERIA 



185 



pletely anaerobic conditions are obtained in the tube and the growth of 

 anaerobes takes place upon the surface of the slant. 



For the cultivation of anaerobes in Petri dishes, for purposes of separa- 

 tion, a combination of the pyrogallic acid method and the hydrogen displace- 

 ment methods is often employed. For this purpose the jars devised by 

 Novy and by Bulloch are extremely convenient. 



In using the Novy jar, the inoculated plates are set upon a wire frame 

 resting about an inch above the bottom of the jar. The cover is then tightly 

 set in place and the air in the jar exhausted by means of a suction pump. 

 The arrangement of the double stop-cock in the top renders it possible now, 

 by simply turning this, to admit hydrogen from a Kipp generator into the 

 jar. The process of alternate exhaustion and admission of hydrogen may 

 be several times repeated. 



FIG. 21. APPARATUS FOR COMBINING THE METHODS OF EXHAUSTION, HYDROGEN 

 REPLACEMENT AND OXYGEN ABSORPTION. 



A combination of air exhaustion, oxygen absorption, and hydrogen replace- 

 ment may be practiced in jars such as that shown in Fig. 21. Dry pyrogallic 

 acid is placed in the bottom of the jar and the cover tightly fitted. An 

 opening in the side of the jar connects its interior with a bottle containing 

 sodium or potassium hydrate solution. Through the stopper of this bottle 

 pass two glass tubes, one of them of such length that it can be pushed 

 down into the alkaline solution, or pulled upward above the level of the 

 fluid. By this means the KOH can be sucked into the jar after a vacuum 

 has been produced with the exhaustion pump. The other glass tube is 

 short, passing just through the stopper and at the top made in the form 

 of a T, one arm of the T being connected with a Kipp hydrogen generator, 

 the other with a suction-pump. 



A simple method for the separation of anaerobes in plates without the 

 use of hydrogen or of specially constructed jars, may be carried out as 

 follows : 10 The apparatus used consists of two circular glass dishes, fitting 



Zinsser, Jour. Exp. Med., viii, 1906. 



