METHODS USED IN CULTIVATION OP BACTERIA 



151 



chamber, are kinked. The entire apparatus may then be incubated. 

 Growth of anaerobic bacteria takes place within the air-tight chamber 

 formed by the short glass tubing within the test tube. The fluid in 

 the test tube, outside of this chamber, usually remains clear. 



When cultivation has been successful, the bacteria may be obtained 

 either for morphological study or for further 

 cultivation, by simply allowing the fluid to 

 flow out of the little air-tight chamber back 

 into the test tube. The method is simple and 

 usually successful. 



Methods Based npon the Displacement of Air 

 by Hydrogen. — ^The principle of air-displace- 

 ment by hydrogen, first utilized by'Hauser,* 

 has been widely applied to the cultivation of 

 anaerobic bacteria. In substance it consists 

 of the conduction of a stream of hydrogen 

 through an air-tight chamber in which plates 

 or tubes containing inoculated media have been 

 placed. 



For the production of the hydrogen, the 

 most convenient apparatus is the Kipp hydro- 

 gen generator or some modification of it. 

 Hydrogen is generated from zinc and sul- 

 phuric acid and this may be passed through 

 a series of Woulfe-bottles, containing solu- 

 tions of lead acetate and of pyrogallic acid, 

 to remove traces of sulphuretted hydrogen 

 and of oxygen, respectively. Some authors 

 recommend also the interpolation of a bottle 

 containing Lugol's solution to absorb traces 

 of acid vapor, and of one with a silver- 

 nitrate solution to take up any hydrogen 

 arsenide which may be derived from impurities 

 contained in the zinc. 



For anaerobic cultivation upon solid media, 

 the inoculated tubes or plates are placed in an apparatus such as 

 the Novy jar. This is connected with the hydrogen apparatus and 

 hydrogen allowed to flow through it for five or ten minutes, and the 

 stop-cocks then closed. 



Fig. 35. — Wright's 

 Method op Anaerobic 

 Cultivation in Fluid 

 Media. 



^Hauser, " Ueber Faulnissbakterien," 1885. 



