92 ANAEROBIC ORGANISMS : ISOLATION AND CULTURE 



8. Yeast flask method— 



This method is specially suitable for the study of anaerobic 

 organisms producing a large quantity of gas, all danger of rupture 

 of the flask being avoided by means of a simple automatic 

 mercury valve. The apparatus consists of a yeast flask as figured, 

 which is filled with milk, glucose bouillon, or other liquid media 

 to about two-thirds of its volume. The mouth is closed with a 

 perforated india-rubber cork, through which is inserted a tightly- 

 fitting glass tube, reaching almost to 

 the bottom of the flask, and extend- 

 ing to 2 or 3 inches above the level 

 of the cork. A constriction is made 

 in the upper portion of this, and above 

 it is inserted a loose cotton-wool plug 

 kept in position by slightly closing 

 the tube orifice in the flame. The 

 whole is then sterilised (except in the 

 case of milk, which should be intro- 

 duced sterile into an already sterilised 

 flask). 



After inoculation, the tube passing 

 down into the medium is connected 

 up with the hydrogen apparatus, and 

 a current of the gas is passed through 

 the liquid for some twenty minutes or 

 half an hour. The extremity of the 

 bent tube is then inserted into a small 

 phial containing a sufficient quantity 

 of mercury to well cover the exit, the 

 longer tube is sealed off at the point 

 of constriction, and the whole placed 

 in the incubator at the temperature desired. The phial of mer- 

 cury forms a valve which, whilst allowing the escape of all gas 

 generated in excess within the flask, effectually prevents the 

 admission of air. 



Fig. 26. 



-Yeast flask culture in 

 hydrogen. 



9. Veillon's method— 



{Glucose agar or glucose gelatine). — Veillon takes advantage of 

 the property of glucose as a reducer of oxygen. Ordinary test- 

 tubes are filled with the medium to two-thirds of their height, 

 and by means of a long needle or very finely drawn glass rod the 

 inoculation is made to the bottom of the tube. To avoid subsequent 



