METHODS FOR THE MICROSCOPIC STUDY OF BACTERIA 213 



plug is pushed into the tube until the upper end is about 15 mm. 

 below the top. The space above the cotton plug is filled loosely with 

 dry pyrogallic acid and a strong solution of sodium hydroxide, 2 to 

 3 c.c., is added to dissolve the acid. Immediately a tightly fitting 

 rubber stopper is inserted into the mouth of the tube. The alkaline 

 pyrogallate solution absorbs the oxygen within the tube, leaving an 

 atmosphere of nitrogen. 



FIG. 30. Incubator. (Park.) 



The addition of bits of fresh, sterile tissue, 1 fresh, sterile defibrinated 

 blood, or of the coagulum which is formed during the coagulation of 

 meat infusion adds greatly to the nutritional value of cultures for the 

 growth of anaerobic bacteria. 



1 Theobald Smith, Cent. f. Bakt., 1890, vii, 502. 



