146 PJiAClVCAL BACTERIOLOGY. 



less, and of short rodlets, consisting of only a few- 

 joints. The motile cells may be stained with simple 

 staining solutions, or, if it is wished to render the 

 flagella visible, by LoflSer's method. Further, during 

 the processes of germination and of the formation of 

 spores, they present a series of conditions which are 

 well worth the trouble of preserving. Also it may be 

 observed that the different nutrient media exert an 

 influence over their form, especially over the thickness 

 of the rods. 



If, after examining a dry cover- glass preparation in 

 water with the microscope, it seems worth preserving, 

 it must be carefully lifted, not drawn, off the slide. 

 If it does not come off easily, a drop of water should 

 be placed at its edge; this penetrates between the 

 cover- glass and the slide, and makes it easy to separate 

 them. If the cover-glass is drawn off, the preparation 

 is usually spoilt. The cover-glass is then put down 

 with the side on which the bacteria are, uppermost, 

 and is allowed to dry in the air ; after that it is 

 passed through a flame, to drive off the last traces of 

 moisture, and is then laid in a drop of Canada balsam 

 on the slide. The Canada balsam is best procured in 

 the form of solid pieces as hard as glass ; it can be 

 dissolved in xylol ; other substances in which it 

 dissolves are less suitable, as they decolourise the 

 preparations. It does not much matter if the pre- 

 parations are made on round or square cover-glasses ; 



