182 



BIOLOGY AND TECHNIQUE 



Methods Based upon the Displacement of Air by Hydrogen. The prin- 

 ciple of air-displacement by hydrogen, first utilized by Hauser, 7 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 hydrogen, the most convenient apparatus is the 

 Kipp hydrogen generated from zinc and sulphuric acid and this may be 



FIG. 18. NOVY JAR. 



passed through a series of Woulfe-bottles, containing solutions of lead 

 acetate and of pyrogallic acid, to remove traces of sulphuretted hydrogen 

 and of oxygen, respectively, of Lugol's solution to absorb traces of acid 

 vapor, and of one with a silver-nitrate solution to take up any hydrogen 

 arsenide. 



For the preparation of anaerobic conditions where very rigid anaerobiosis 

 is necessary, nitrogen may be used, which can be bought in tanks from com- 

 mercial firms. 



Hauser, ( i Ueber Faulnissbakterien, ' ' 1885. 



