1806 



Journal of Applied Microscopy 



Fig. 48. 



Method. — Boil the medium 

 in flask (a) and in porcelain 

 dish (d) for one-half hour 

 simultaneously to drive the 

 atmospheric oxygen from the 

 medium. The evolving vapor 

 forces the medium out of the 

 flask, but the liquid thus freed 

 from air returns back into the 

 flask. The process repeats 

 itself several times during the 

 boiling. When boiled for the 

 required length of time cool 

 apparatus and medium. While 

 cooling cover the medium in 

 the porcelain dish with a layer 

 of sterile oil to prevent a sub- 

 sequent absorption of oxygen 

 from the air. Fill (f ) with the culture material and seal with the rubber stop- 

 per. When apparatus and medium are cool introduce a part of the culture 

 material from reservoir (f ) into the medium by quickly opening and closing turn 

 cock (e). The latter must fit perfectly. Now submerge the outer end of tube 

 (b) in sterile mercury for the purpose of collecting the gases formed by the bac- 

 terial activity, and place the apparatus in the incubator. For a control test the 

 author uses a flask as shown in Fig. 49. It is twice as large as that shown in 

 Fig. 48, and filled only one-half with medium so that the culture is freely exposed 

 to atmospheric oxygen. 



Smith found the fermentation tube to be an ap- 

 paratus of considerable antiquity and of unknown 

 origin. He says : " In Detmer's pflanzenphysiolo- 

 gischem Practicum I find it figured as Kiihnesches 

 Gahrungsgefass. More recently it has been adapted 

 by Einhorn for the quantitative determination of sugar 

 in urine and by Doremus for that of urea in the same 

 fluid." Smith, in 1889, first conceived the value and 

 made practical application of this tube with reference 

 to anaerobioses and gas-formation among bacteria. 

 The illustration (Fig. 50) represents a model fer- 

 mentation tube. With regard to its construction 

 Smith says : " In the construction of this simple bit of 

 apparatus several points must be borne in mind. The 

 bulb should be large enough to receive all the fluid con- 

 tained in the closed branch. Moistening the plug im- 

 perils the purity of the culture. If the bulb is sufficiently large this difficulty 

 will not arise. The connecting tube should not be too small, for then the filling 

 and emptying of the closed branch becomes very tedious. Nor should it be too 



Fig. 49. 



