MANUAL OF BACTERIOLOGY. 



parts are drawn to a small caliber at some point, although not quite closed, to 

 facilitate sealing later on. Through the longer of these tubes hydrogen gas is 

 passed until the atmosphere inside of the culture-tube is pure hydrogen, entirely 

 free from mixture with air. The horizontal parts of the small glass tubes 

 projecting from the stopper are then sealed in the flame at the places where they 

 were previously drawn out to a small caliber, and the tubes are thus closed. 

 (Fig. 27.) 



The stopper should be surrounded with melted paraffin. A tube prepared 

 according to this plan may, if desired, be converted into an Esmarch roll-tube. 

 The hydrogen is generated according to the common method with pure zinc 

 and pure sulphuric acid, 25 to 30 per cent. The precautions advised by chem- 

 ists for the generation of hydrogen 

 must be carefully followed because 

 when hydrogen mixed with oxygen 

 or air is ignited a violent and 

 disastrous explosion may occur. 

 Those unfamiliar with the genera- 

 tion of hydrogen should seek the 

 aid of someone who is informed so 

 as to avoid accidents arising from 

 explosion. The hydrogen must 

 not be allowed to escape in the 

 neighborhood of a flame for fear 

 of explosion. 



The well-known Kipp's gener- 

 ator may be used. First let the 

 reservoir fill with hydrogen; then 

 allow its contents to escape. This 

 should be repeated, after which 

 some of the hydrogen may be 

 collected, in an inverted test-tube 

 under water. When this sample is 

 ignited, it should burn without any 

 explosion; for if it explodes this shows that oxygen is still mixed with it. The 

 hydrogen should bubble through the medium five minutes or more. 



The inconvenience and danger of sealing the tubes in the flame, as has to be 

 done in Liborius-Frankel's and other methods for cultivation under hydrogen, 

 are obviated in Navy's apparatus. The tubes or plates are placed in jars 

 through which hydrogen may be conducted. The stopper, having been smeared 

 previously with a soft wax, is sealed by giving it one-fourth of a turn. 



There have been various other kinds of apparatus, usually complicated and 

 expensive, devised for the growth of plate-cultures under hydrogen, but Novy's 

 jars are the best, both for tubes and for plates. 



Other expedients for the cultivation of anaerobic bacteria are less effective. 



FIG. 30. Novy's jar for the cultivation 

 of anaerobes. 



