190 BACTERIOLOGY, 



the operation the tube containing the liquefied gelatin 

 should be kept in a water-bath at a temperature suffi- 

 ciently high to prevent its solidifying, and at the same 

 time not high enough to kill the organisms with which 

 it has been inoculated. 



One of the obstacles to the successful performance of 

 this method is the bubbling of the gelatin, the foam 

 from which will often fill the exit tube and sometimes be 

 forced from it. This may be obviated by reversing the 

 order of proceeding, viz. : Prepare the Esmarch roll 

 tube in the ordinary way with the organisms to be 

 studied, using a relatively small amount of gelatin, so 

 as to have as thin a layer as possible when it is rolled. 

 Then replace the cotton plug with the sterilized rubber 

 stopper carrying the glass tubes through which the 

 hydrogen is to be passed, and allow the hydrogen to 

 flow through just as in the method first given. The 

 gas now passes over the gelatin instead of through it, 

 and consequently no bubbling results. In all other 

 respects the procedure is the same as that given by 

 Frankel. 



Method of Kitasato and Weil. For favoring the 

 anaerobic conditions, Kitasato and Weil have suggested 

 the addition to the culture media of some strong re- 

 ducing agent. They recommend formic acid in 0.3 to 

 0.5 per cent.; glucose in 1.5 to 2 per cent., or blue 

 litmus tincture in 5 per cent, by volume. This is, of 

 course, in addition to an atmosphere from which all 

 oxygen has been expelled. 



Esmarch' s method. Esmarch's plan is to prepare in 

 the usual way a roll tube of the organisms ; subject it 

 to a low temperature, and while quite cold fill it with 

 liquefied gelatin, which is caused to solidify t rapidly. 



