134 Manual of Veterinary Microbiology. 



Anaerobic cultures. — Anaerobic germs, in order to 

 grow, must be protected from the air; before attempt- 

 ing cultivation, therefore, it is necessary to remove 

 the oxygen from the atmosphere and the medium in 

 which these are expected to develop. This is accom- 

 plished in various ways. The best method consists 

 in creating a vacuum in the culture apparatus and 

 replacing the air with carbonic acid or hydrogen. 

 This operation is repeated several times in order to 

 insure the complete removal of the air. Gelatin 

 must be fluidified before it is deoxygenated. When 

 the operation is completed the culture vessel is sealed 

 in the flame. 



The oxygen of the air can be abstracted by sealing 

 the culture tube within a second, containing sub- 

 stances which rapidly absorb oxygen, such as pyro- 

 gallic acid with the addition of a solution of caustic 

 potash. Sometimes, also, we add to the culture 

 media substances capable of taking up oxygen; for 

 example, neutralized sulfate of indigo.* 



* [Anaerobic cultures can also be conveniently carried on in 

 small closed tubes completely filled with culture medium. These 

 tubes may be filled in various ways; the following method of 

 preparation and use is that which I have found most satisfactory: 

 A piece of glass tubing about h cm. in diameter and 10 to 15 cm. 

 in length is sealed at one end in the flame of a blow-pipe, heated 

 throughout sufficiently for sterilization, drawn out at the other 

 end to a thickness of from 1 to 2 mm., and sealed at a point about 

 6 cm. from the thicker part of the tube. The evacuation of the 

 air in the tube is obtained by the ebullition of alcohol. A few 

 drops are allowed to ascend (by slightly heating the tube, break- 

 ing off the point and immersing it in the fluid), shaken to the 

 bottom and the tube then held in the flame of a Bunsen burner. 

 Long forceps, the points of whi(!h are wrapped in asbestos, are 

 most suitable for this purpose. The essential points in this process 



