CULTIVATION OF ANAEROBIC BACTERIA. 73 



wash. tLe corrosive sublimate from the india-rubber 

 stopper with sterilised water, and dry it upon cotton- 

 wool, which, was sterilised with the tubing in the hot- 

 air apparatus. The cotton-wool plug is then removed 

 from the test-tube, and the india-rubber stopper, into 

 which the sterilised glass tubes are quickly placed, is 

 inserted. The longer of the two tubes is then con- 

 nected with a hydrogen generating apparatus which, 

 if the hydrogen is to be pure, must be arranged in the 

 following manner. Chemically pure granulated zinc 

 is placed in a small Kipp's apparatus and dilute 

 chemically pure sulphuric acid is poured over it. 

 Hydrogen is evolved, and is conducted through three 

 flasks, the first containing an aqueous solution of 

 lead nitrate, to absorb all traces of sulphuretted 

 hydrogen ; the second, nitrate of silver,^ to absorb the 

 arseniuretted hydrogen; and the third alkaline pyro- 

 gallic solution, to absorb the last traces of oxygen. 

 The tube conducting the hydrogen is then connected 

 with the one from the test-tube. The india-rubber 

 stopper is covered over with a thick layer of paraffin 

 to stop up all cracks and fissures between the stopper 

 and the tubes, etc., thus making the apparatus 

 absolutely air-tight, and preventing the hydrogen 



sublimate solution (1 ; 1000). The towel used for drying 

 them must also have been sterilised in the steam steriliser. 

 * Or silver sulphate. 



