Displacement of the Air by Inert Gases 209 



leaves no vacuum. It is easier to displace the oxygen than 

 to withdraw it, and any apparatus permitting a combina- 

 tion of both features, as that designed by Ravenel,* from 

 which the air can be sucked by a pump, to be later replaced 

 by hydrogen, can be viewed with favor. 



The most simple apparatus of the kind was suggested by 

 Frankel (Fig. 52), who inoculated a culture-tube of melted 

 gelatin or agar-agar, solidified it upon the wall of the tube, as 

 suggested by Esmarch, substituted for the cotton stopper a 

 sterile rubber cork containing a long entrance and short 

 exit tube of glass, passed hydrogen through the tube until 

 the oxygen had been entirely removed, then sealed the 

 ends in a flame. In this tube the growth of superficial and 

 deep colonies can be observed. Hansen and Liborius con- 



Fig. 51. Novy's jars for anaerobic cultures. 



structed special tubes (Fig. 53) by fusing a small glass tube 

 into the wall of a culture-tube, and narrowing the upper part 

 of the tube in a flame. After inoculation, hydrogen is passed 

 into the small tube and permitted to escape through the 

 mouth of the large tube until the air is entirely replaced, 

 after which both tubes are sealed in a flame. 



Instead of having a special apparatus for each culture, it 

 is far better to adapt the principle to some larger piece of 

 apparatus that can contain a number of tubes or Petri dishes 

 at a time. For this purpose the jar invented by Novy or the 

 apparatus of Botkin can be used. 



The Novy jar receives as many inoculated tubes as it will 



*" Bacteria of the Soil," "Memoirs of the National Academy of 

 Sciences," First Memoir, 1896. 



