THE CULTIVATION OF MICRO-ORGANISMS 125 



Liborius, which seems to have been used first by Veillon. Several 

 tubes of glucose agar are melted, cooled to 45 C. and then in- 

 oculated by dilution in series just as if plate cultures were to be 

 made. After careful mixing the agar is quickly congealed by 

 standing the tubes in cold water. The later tubes in the series 

 should contain only a few bacteria so that single colonies may 

 develop. The method serves for anaerobes and also for those 

 kinds of bacteria which seem to require some free oxygen but do 

 not grow well when exposed to the full amount in the atmosphere 

 (B. abortus, B. bifidus). 



Fermentation Tube. Anaerobic bacteria grow excellently 

 in the Smith fermentation tube filled with glucose broth, especially 

 if a small piece of naturally sterile liver or kidney from a small 

 animal, or a few cubic centimeters of naturally sterile defibrinated 

 blood be added to the medium in the tube. Glucose gelatin 

 to which litmus has been added also furnishes a medium in which 

 anaerobes will grow abundantly without any special precautions 

 to protect them from oxygen or from the air. 



Removal of Oxygen. Anaerobic conditions may be furnished 

 by pumping out the air from a container in which the cultures 

 have been placed, a method employed by Pasteur. The oxygen 

 may be absorbed from the air by a mixture of pyrogallic acid 

 and alkali. Buchner's method is carried out as follows: Into 

 a bottle or tube which can be tightly stoppered, pour 10 c.c. of a 

 6 per cent solution of sodium or potassium hydroxide, for each 

 100 c.c. of air contained in the jar. Add one gram of pyrogallic 

 acid for each 10 c.c. of solution. The culture-tube is placed 

 inside of the larger bottle or tube, supported above the bottom, 

 and the stopper, smeared with paraffin, is inserted. The mix- 

 ture of pyrogallic acid and potassium hydroxide possesses the 

 property of absorbing oxygen. 



Wright's Modification of Buchner's method: The tube of cul- 

 ture-medium is to be plugged with absorbent cotton, using a plug 

 of large size. The culture-medium is inoculated in the usual 

 way. The plug is cut off close to the neck of the tube, and is 



