and Laboratory Methods. 



1751 



III. 



ABSORPTION OF ATMOSPHERIC OXYGEN. 



To this category belong all those methods, in which advantage is taken of 

 the oxygen-absorbing power of some chemical agents. The adoption of this 

 principle for the purpose of bringing about anaerobic conditions is of more recent 

 date than that of exhaustion and of replacement by inert gases. 



In 1878 Gunni7ig used a mixture of a ferro salt with an excess of sodium 

 hydroxide. He also recommended a solution of glucose containing indigo car- 

 mine and sodium hydroxid. 



In 1880 Nenki found that anaerobic bacteria grow well in an atmosphere from 

 which the oxygen has been absorbed by an alkaline solution of 

 pyrogallic acid. Practical application of this principle, however, 

 was not made until 1888, when Buchner invented the method 

 which now carries his name. 



Buchner' s Method. — Use two test tubes of different sizes (see 

 Fig. 30), drop into the large tube a small wire support on which 

 the small tube is subsequently placed. The small test tube con- 

 tains the inoculated medium and is closed with a loose cotton 

 plug. Put into the large test tube one gram of dry pyrogallic acid 

 and then ten c. c. of a one-tenth solution of potassium hydroxid 

 (1 part Liquor Kali caust. to 10 parts of water). Then quickly 

 lower the small culture tube and close the latter hermetically with 

 a new, elastic, well fitting, paraffined rubber stopper. Shake 

 well. Buchner observed that the above stated amount of pyro- 

 gallic acid and potassium hydroxid will completely absorb the 

 oxygen in a tube with a cubic content of 100 c. c. in 24 hours at 

 incubator temperature. At lower temperatures, as for instance in 

 the refrigerator, the absorption of oxygen is much slower. Fre- 

 quent shaking hastens the absorption. 



For plate cultures Buchner incloses the plates filled with the 

 inoculated medium under a hermetically sealed bell jar and uses larger amounts 

 of pyrogallic acid and potassium hydroxid. 



Babes and Fuscarin in 1890 modified Buchner's method by putting the inoc- 

 ulated culture tubes into a Fresinius desiccator containing a large amount of 

 pyrogallic acid and potassium hydroxid. After closing the desiccator hermetic- 

 ally with a vaselined ground glass plate, the apparatus is put into the incubator. 

 This method enables the experimenter to cultivate numerous tube cultures sim- 

 ultaneously and under identical conditions. The authors obtained the best re- 

 sults when they used media containing 2 per cent, glucose. 



Blucher (1890) recommends the following method for plate cultures : 



Put a petri dish 6 cm. in diameter, minus cover, into a glass saucer 10 cm. 

 in diameter and 4 cm. high. The upper edge of the saucer is ground convexly 

 and it fits exactly into a cover with a concave rim. Into the outer saucer pyro- 

 gallic acid and potassium hydroxid are placed and the cover, the concave panel 

 of which has been well vaselinated, is inverted over the saucer. The decrease 



Fig. 30. 



