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 (6) 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.