METHODS USED IN CULTIVATION OF BACTERIA 



181 



slowly diffuses through the oil into the medium below. In using paraffin 

 oil on anaerobic cultures it must be remembered that liquid oil is a very 

 incomplete seal and that solid paraffin or any other solid seal is much more 

 efficient. 



The simple exclusion of air, also, is the principle underlying the cultiva- 

 tion of anaerobic bacteria in the closed arm of a Smith fermentation tube. 



WRIGHT'S METHOD. 6 Wright has described a simple and excellent method 

 for the cultivation of anaerobic bacteria in fluid 

 media. The apparatus necessary is easily im- 

 provised with the materials at hand in any 

 laboratory. A short piece of glass tubing, con- 

 stricted at both ends and fitted at each end with 

 a small piece of soft-rubber tubing, is inserted 

 into a test tube containing nutrient broth. The 

 upper end of the inserted glass tubing is con- 

 nected by the rubber with a pipette passed 

 through the cotton plug in the tube. The entire 

 apparatus, plus broth, may be sterilized after 

 being put together. When a transplant is made, 

 the fluid in the test tube is inoculated as usual. 

 The fluid is then sucked up into the glass tubing 

 until this is completely filled. A downflow of 

 the fluid is then prevented by placing the finger 

 over the pipette through which the suction has 

 been made or by constricting a small piece of 

 rubber tubing attached to the upper end of the 

 pipette. The entire system of tubes is then 

 pushed downward in such a way that both pieces 

 of rubber tubing, attached to the ends of the 

 little glass chamber, are kinked. The entire 

 apparatus may then be incubated. Growth of 

 anaerobic bacteria takes place within the air- 

 tight chamber formed by the short glass tubing 

 within the test tube. The fluid in the test tube, 

 outside of this chamber, usually remains clear. 



When cultivation has been successful, the 

 bacteria may be obtained either for morphological 

 study or for further cultivation, by simply allowing the fluid to flow out 

 of the little air-tight chamber back into the test tube. The method is 

 simple and usually successful. 



FIG. 17. WRIGHT'S METHOD 

 OF ANAEROBIC CULTIVATION 

 IN FLUID MEDIA. 



6 Wright, J. II. Quoted from Mallory and Wright, "Path. Technique/' Phila., 

 1904. 



