68 METHODS OF CULTIVATION OF BACTERIA 



exit tube, and letting the end just dip into a trough of mercury 

 (Fig. 25), or into mercury in a little bottle tied on to the end 

 of the exit tube. The pressure of gas within causes an escape 



at the mercury contact, 

 which at the same time acts 

 as an efficient valve. The 

 method of culture in fluid 

 media is used to obtain the 

 soluble products of such 

 anaerobes as the tetanus 

 bacillus. 



The Method of Tarozzi. 

 This observer has found that 

 if small pieces of fresh 

 sterile organs are added to 

 ordinary bouillon, growth of 

 anaerobes takes place under 

 ordinary atmospheric con- 

 ditions. For this purpose, 

 portions of liver, spleen, or 

 kidney are most suitable. 

 If after the piece of tissue has been added the medium is boiled 

 for a few minutes it loses its property of growing anaerobes, 

 but the temperature may be raised for a short time almost to 

 boiling-point without this occurring. The tissue of the organs 

 gives off something into the medium which favours the growth 

 of anaerobes, as can be shown by placing the tissue for some 

 time in the medium and then removing it; thereafter the 

 medium is suitable for anaerobic growth. 



When it is desired to grow anaerobes on the surface of a 



FIG. 25. Flask arranged for culture of 

 anaerobes which develop gas. 



b is a trough of mercury into which 

 exit tube dips. 



FIG. 26. Tubes for anaerobic cultures on the surface of solid media. 



solid medium such as agar, tubes of the form shown in Fig. 26, 

 a and b, may be used. A stroke culture having been made, the 

 air is replaced by hydrogen as just described, and the tubes are 



