312 BACTERIOLOGY. 



mouth of the tube, and, the plug 1 is slightly raised with 

 sterilized forceps in order to facilitate diffusion of the gas. 

 The inoculated tubes are then placed in the bottle by means 

 of a pair of forceps (Fig. 46), and the apparatus is now con- 

 nected with a Kipp's hydrogen generator. The current of 

 hydrogen shonld be passed, first, through an alkaline solu- 

 tion of lead acetate, then through a six per cent, solu- 

 tion of potassium permanganate, and finally through a solu- 

 tion of silver nitrate. After passing through the apparatus 

 the gas passes through a small wash-bottle containing 

 water, which serves as a valve. A rapid current of gas is 

 passed through the bottle for 1 to 2 hours. The bottle is 

 then sealed by turning the stopper, and is set aside in the 

 incubator. 



The hydrogen is generated from ordinary granulated zinc by 

 means of commercial sulphuric acid. The stopper should not be 

 greased with vaselin, but with a mixture of bees-wax and olive oil 

 (1-4). Before applying the lubricant, it is advisable to spread a layer 

 of cotton over the bottom of the flask. Rubber bands should be slip- 

 ped over the stopper and around the lateral tubes. This is to prevent 

 the stopper from being raised by the pressure of the confined gases 

 when the apparatus is placed in the incubator. 



When the cultures have developed they should be taken out of 

 the bottle and preserved the same as ordinary bacteria. Care should 

 be exercised when removing the stopper so as to avoid breakage. It 

 should first be turned so as to allow air to enter. At the same time the 

 rubber bands are removed. The thumb and forefinger of the left hand 

 should rest firmly on the shoulder of the stopper, while this is grad- 

 ually worked to and fro with the right hand. This little precaution 

 will prevent the sudden jerking out of the stopper. 



The pyrogallate method can be used in connection with this bot- 

 tle. 2-3 g. of the acid can be placed on the bottom, the inoculated 

 tubes then inserted, and finally the necessary concentrated alkali can 

 be delivered from a pipette. The stopper should then be inserted at 

 once and turned at right angles. 



Fig's. 52 and 53 show two forms of apparatus for obtain- 

 ing- plate cultures. The former is provided with a stopper 

 like that in the bottle just described. This apparatus can 



