94 ANAEROBIC ORGANISMS : ISOLATION AND CULTURE 



sterile india-rubber stopper pierced by one hole, through which is 

 inserted a piece of narrow glass tubing con- 

 j^ stricted as shown, and plugged lightly with cotton- 



m wool between the two constrictions. Thoroughly 



sterilise this latter in the flame before passing it 

 through the stopper, and moisten with benzole to 

 secure an air-tight joint. Inocu- 

 late the potato in the ordinary 

 manner with a spatula-shaped 

 needle, replace the stopper, and 

 apply with a camel's hair brush, 

 a few drops of benzole, or a mix- 

 ture of paraffin and vaseline pre- 

 viously melted, in order to secure 

 an air-tight joint. Connect the 

 inlet-tube with the india-rubber 

 tubing of the hydrogen appar- 

 atus, exhaust by means of the 

 air pump, wash some four or 

 five times with hydrogen as 

 described above (p. 83), and 

 seal off (either in vacuo or in 

 hydrogen) at the upper con- 

 striction.^ When it is required 

 to open the tube for examina- 

 tion or reculture, it is only 

 necessary to break off the ex- 

 treme point of the inlet-tube 

 and allow the air to filter in 

 through the cotton-wool plug. 

 The stopper can then be re- 

 moved and a platinum needle 

 inserted in the ordinary manner, 

 after which, if desired, the stop- 

 per can be replaced, the air 



^ The ordinary method is to seal 

 off at the lower constriction, in which 

 case the opening of the tube causes 

 almost certain contamination by the 

 inrush of unfiltered air. By sealing 



oflfthe upper constriction first this is avoided, and the tube can be re-exhausted 



if it is desired to proceed further with the culture. 



Fig. 27. — Potato 

 culture in vacuo. 



Fig. 28. — Agar cul- 

 ture in vacuo. 



