CULTIVATION OF ANAEROBIC BACTERIA. 157 



but when the stopper is turned a little the jar is hermet- 

 ically sealed. Alkaline pyrogallic acid in a test-tube, or 

 in the bottom of the jar, will serve to absorb any remain- 

 ing oxygen. The larger jar (Fig. 39, a) is intended for 

 Petri dishes, the smaller one (b) for test-tube cultures. 

 Roux has suggested the simplest method of cultivating 

 anaerobic bacteria. The germs are distributed through 

 freshly boiled, still liquid, gelatin or agar-agar, as in 

 making the dilutions for plate-cultures, then drawn into 

 a long, slender sterile piece of glass tubing of small 

 calibre. When the tube is full the ends, which should 

 have been narrowed, are closed in a flame, and the cul- 

 ture is hermetically sealed in an air-tight chamber. The 

 chief difficulty is in transplanting the growing colony. 

 To do this the tube must be opened with a file or a dia- 

 mond at the point where the colony desired is observed. 



