FERMENTATION TUBES 



one extremity, blowing a small bulb at the centre, and 

 plugging the open end with cotton-wool ; after sterilisa- 

 tion the open end is provided with a short piece of 

 rubber tubing and a glass mouthpiece. When it is 

 necessary to observe sedimentation reactions in very 

 small quantities of fluid, these tubes will be found 



FIG. 20. Sedimentation pipette. 



much more convenient than the 5 by 0.5 cm. test-tubes 

 previously mentioned. 



Pasteur pipettes fitted with india-rubber teats will 

 also be found useful for sedimentation tests when 

 dealing with minute quantities of serum, etc. 



Fermentation Tubes (Fig. 21). These are used for 

 the collection and analysis of the gases liberated from 



a b c 



FIG. 21. Fermentation tubes. 



the media during the growth of some varieties of bac- 

 teria and may be either plain (a) or graduated (b). 

 A simple form (Fig. 21, c) may be made from 14 

 cm. lengths of soft glass tubing of 1.5 cm. diameter. 

 The Bunsen flame is applied to a spot some 5 cm. from 

 one end of such a piece of tubing and the tube slightly 

 drawn out to form a constriction, the constricted part 



