ESMARCH'S METHOD. 179 



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 organism 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 solid 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 O.B 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. 



JlJsmarch'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 rapidly. 

 In this method the colonies develop along the sides of 

 the tubes, and can -more easily be studied than where 

 they are mixed through the gelatin, as in the method 

 of Liborius. 



By some workers the oxygen is removed by actual 

 pumping with the air-pump. 



Many other methods exist for this special purpose, 

 but for the beginner those given will suffice. 



