74 



ESSENTIALS OF BACTERIOLOGY 



solidified, the surface is inoculated with a small quantity of 

 Bacillus subtilis or some other aerobic germ. The subtilis does 

 not allow the oxygen to pass by, appropriating it to itself. 



Buchner's Method. The test-tube 

 containing the culture is placed within 

 a larger tube, the lower part of which 

 contains an alkaline solution of pyro- 

 gallic acid. The tube is then closed 

 with a rubber stopper (Fig. 43). 



Botkin's Method. Petri dishes, 

 uncovered, are placed on a rack under a 

 large bell-jar, into which hydrogen gas 

 is conducted. Alkaline pyrogallic acid 

 is placed in the upper and lower dishes 

 to absorb what oxygen remains. 



Wright's Method. Applicable to 

 both fluid and solid media. After in- 

 oculating the test-tube, the plug, which 

 must be of absorbent cotton, is cut off 

 flush with the extremity of the tube, 

 and pushed inward for a distance of i 

 cm. It is then impregnated with i c.c. 

 of a watery solution of pyrogallic acid 

 and T c.c. of 5 per cent, sodium hydroxid 

 solution. A tightly fitting rubber stop- 

 per is inserted, and the tube is then 

 ready for incubation. (See Fig. 44.) 

 Park's Method. An Erlenmeyer 

 flask containing the medium to be used 

 is boiled in a water-bath from ten to 

 fifteen minutes to drive off dissolved 

 oxygen, quickly cooled, and inoculated. 



Hot melted paraffin is then poured into the flask, which forms 

 a layer over the medium, and on congealing, provides an air- 

 tight seal which does not adhere to the glass so closely as to 

 prevent the escape of any gases formed by the bacterial 

 growth. 



Fig. 44. Wright's 

 method for the cultivation 

 of anaerobes. 



