152 



BIOLOGY AND TECHNIQUE 



In applying the hydrogen method to fluid media, flasks containing 

 the broth are fitted with sterile, tightly fitting rubber stoppers per- 

 forated by two holes, through which glass tubes are passed. One of 

 these tubes, the inlet, passes below the surface of the liquid. The other 

 one, the outlet, extends only a short distance below the stopper and is 

 always kept above the surface of the medium. The flasks are inoculated 

 and hydrogen is passed through the medium so that it enters the 

 long tube, bubbles up through the fluid, and leaves by the short tube. 



The broth may be covered with a 

 thin layer of liquid paraffin or 

 albolin. 



The Use ol Pyrogallic Acid 

 Dissolved in Alkaline Solutions 

 for Oxygen Absorption. — Buchner' 

 has applied the principle of 

 chemical absorption for the re- 

 moval of oxygen to the cultiva- 

 tion of anaerobic bacteria. This 

 has been made use of in a 

 number of different ways. The 

 method is based upon the fact 

 that alkaline solutions of pyro- 

 gallol possess the power of ab- 

 sorbing large quantities of free 

 oxygen. At first such solutions 

 are of a light straw-color, which 

 becomes dark brown as oxygen 

 is absorbed. The absorption of 

 all the oxygen in the environ- 

 ment may be assumed when 

 there is no further deepening of 

 the brown color. 



Buchner first utilized this 

 principle by placing a small wire or glass holder within a large test 

 tube, dropping dry pyrogallol (pyrogallic acid) into the bottom of this 

 tube, then running a five per cent sodium hydrate solution into it, 

 and inserting within this large tube a smaller test tube containing the 

 inoculated culture medium. The large tube was then tightly closed 



Fig 36.— Novy Jar. 



1 Buchner, Cent. f. Bakt., I, iv, 1888. 



