NUTRIENT MEDIA -AND METHODS OF CULTIVATION. 



131 



process very little air re-enters the jelly, and colonies of even strictly 

 anaerobic bacteria will develop in the lower part of the tube. The 

 drawback is the difficulty encountered in examining the colonies, 

 and in preparing sub-cultures. For this purpose the tube 

 must be broken, or carefully warmed until the jelly can be 

 shaken out. 



Esmarch first prepares a roll culture, and when the gelatine film, 

 has set, the tube is completely filled with liquefied gelatine which has 

 been cooled down almost to the temperature at which it solidifies. The 

 same diflficulty arises £ 

 in the previous method, in 

 the examination of the 

 colonies. 



Buchner places the 

 culture tube inside a much 

 larger tube containing a 

 small quantity of pyro- 

 gallic acid and closed with 

 a gutta-percha cap. The 

 pyrogallic acid absorbs the 

 oxygen, but the method 

 is not altogether success- 

 ful. 



The most satisfactory 

 plan is to exhavist the air 

 with an air pump, or to 

 substitute an atmosphere 

 of hydrogen which does 

 not affect the growth of 

 the bacteria. 



"Various forms of flasks 

 and tubes for cultivating ^^^ ee.-FBANKEL's Anaekoeio Tube-culture" 

 bacteria have been devised, jj_„^ gjass tube through which hydrogen is 

 which can be easily con- passed; b, exit tube; e, india-rubber 



nected with an exhausting ^^X^LANnr "*""''" "^'^ '""*'' 



apparatus, and • readily 



sealed by the flame of the blowpipe when the air has been removed. 



If hydrogen is employed the most convenient plan is to use 

 a Zipp's apparatus, from which the hydrogen is passed through 

 two bottles, one containing a solution of lead, to remove any 

 sulphuretted hydrogen, and the other pyrogallic acid, to intercept 

 any oxygen. 



