MICROSCOPICAL EXAMINATION OF BACTERIA. 51 



allowed to fall from a pipette upon the film. The 

 cover-glass with the drop of stain is after a minute 

 carefully turned over on to a slide, and the excess 

 of stain gently and gradually removed by pressure 

 with a strip of filter paper. It affords a rapid 

 means of demonstration, for example of such a 

 cultivation as Koch's comma bacilli in nutrient 

 gelatine, enabling the microbes to be seen in some 

 parts of the preparation both stained and in active 

 movement. 



His' Method. The staining of fresh prepara- 

 tions, especially those with no coagulable albumen 

 to fix them, may be also carried out by His' method. 

 A slide is prepared as already described in the 

 examination of micro-organisms in the fresh state. 

 The reagents are then applied by placing them 

 with a pipette drop by drop at one margin of 

 the cover-glass, and causing them to flow through 

 the preparation by means of a strip of filter paper 

 placed at the opposite margin. 



To stain spores the method described on p. 48 

 is somewhat modified. The cover-glass prepara- 

 tions may be either passed as many as twelve times 

 through the flame, or heated to a temperature of 

 2 10 for half-an-hour, or exposed to the action of 

 strong sulphuric acid for a few seconds, and then 

 stained with a watery solution of the dye. 



To double-stain spore-bearing bacilli. The 

 cover-glass preparations may be floated for twenty 

 minutes on a fuchsine aniline- water solution, as 



