140 



BACTERIA 



the hydrogen to its desired destination. With some it is the 

 custom to place anaerobic cultures in test-tubes, and the 

 test-tubes in a large flask having a two-way tube for en- 

 trance and exit of the hydrogen; others prefer to pass the 

 hydrogen immediately into a large test-tube containing 



the culture (Frankel's method). 

 Either method ends practically 

 the same, and the growth of 

 the culture in hydrogen is read- 

 ily observed. Yet another plan 

 is to use a yeast flask, and after 

 having passed the hydrogen 

 through for about half an hour, 

 the lateral exit tube is dipped 

 into a small flask containing 

 mercury. The entrance tube is 

 now sealed, and the whole ap- 



Cultivation Flask 



The Zinc and Acid Vessel 



Kipp's Apparatus 



For the Production of Hydrogen 



paratus placed in the incubator. The interior containing 

 the culture is filled with an atmosphere of hydrogen. No 



