106 Animal Micrology 



sterilized water or bouillon is put on the cover-glass to facilitate the 

 spreading of the bacteria in a film over the cover. 



II. Staining and Mounting. 



1. Gentian violet (memorandum 3 a) 5 minutes. The cover-glass is 

 left in the forceps, film side up, and the film flooded with the staining 

 fluid. 



FIG. 38. Cornet's Cover-Class Forceps. 



2. Rinse in water. 



3. Gram's solution (memorandum 3/) until the color becomes black 

 (2 to 3 minutes). 



4. Ninety-five per cent, alcohol until the violet color has almost com- 

 pletely disappeared. 



5. Rinse in water and examine by placing the cover-glass film side 

 downward on a slide. Only a thin film of water should remain between 

 the slide and the cover. Remove surplus water by means of blotting 

 paper. If a prolonged examination is to be made, water lost by evapora- 

 tion must be replaced by occasionally placing a small drop of water at 



FIG. 39. Stewart's Steel Wire Cover-Glass Forceps. 



the edge of the cover. In ordinary work the final inspection is frequently 

 made at this stage. If a permanent preparation is desired, however, 

 proceed with the following steps : 



6. If the bacteria are well stained, a counterstain of Bismarck brown 

 (memorandum 3d, sol. 2) may be added (5 to 10 seconds). This step may 

 be omitted. 



7. Absolute alcohol, 10 to 15 seconds. 



8. Xylol. 



9. Xylol-balsam. 



NOTE. In staining, if the cover-glass is warmed over a flame some 

 15 or 20 seconds until the stain steams, the action of the stain is usually 

 more intense and more rapid. Boiling, however, must be avoided. 



