METHODS USED IN CULTIVATION OF BACTERIA 153 



with a rubber stopper. In this way, the air space surrounding the 

 smaller tube was rendered oxygen free. 



A simple modification of the preceding method of Buchner has 

 been devised by Wright. 1 Stab-cultures of gelatin or agar in test 

 tubes are made in the usual way. The cotton stopper closing the tube 

 is then thrust into the tube to such a depth that its upper end lies at 



least 1 cm. below the mouth of the tube. 



A small quantity of sodium or potassium 

 hydrate solution in which some pyrogallic 

 acid has been dissolved, is then allowed to 

 flow on to the cotton of the plug and the 

 mouth of the tube is immediately sealed by 

 a tightly fitting rubber stopper. The cotton 

 stopper in these cases must be made of ab- 

 sorbent cotton; 1.5 to 2.5 c.c. of the pyro- 

 gallic acid solution is usually sufficient for 

 test tubes of ordinary size. 



For cultivation of anaerobic bacteria 

 upon agar slants, a simple technique may be 

 applied and easily improvised in the labora- 

 tory as follows: The tube of slant agar is 

 inoculated with the infectious material in the 

 usual way. It is then, with stopper removed, 

 inverted into a tumbler ^or beaker containing 

 about a gram of dry pyrogallic acid. A 

 small quantity of a five per cent or three 

 per cent sodium hydrate solution is then run 

 into the tumbler and this is covered with a 

 thin layer of liquid paraffin or albolin before 

 the pyrogallic acid has been completely dis- 

 solved. In this way, completely anaerobic 

 conditions are obtained in the tube and the 

 growth of anaerobes takes place upon the 

 surface of the slant. 



For the cultivation of anaerobes in Petri 



dishes, for purposes of separation, a combination of the pyrogallic 

 acid method and the hydrogen displacement methods is often em- 

 ployed. For this purpose the jars devised by Novy and by Bulloch 

 are extremely convenient. 



1 Wright, Jour, of the Boston Soc. of Med. Sci., Dec., 1900. 



FIG. 37. WRIGHT'S METH- 

 OD OF ANAKKOBIC CULTIVA- 

 TION BY THE USE OF PYRO- 

 GALLIC ACID SOLUTION. 



