GENERAL METHOD OF STAINING SPECIMENS 55 



upon the cover-glass so that the whole specimen is covered, 

 and the stain is left on a few minutes, the time depending 

 upon the variety, the strength of stain, and the object de- 

 sired. Instead of placing the dye upon the object, the cover- 

 glass can be immersed in a small glass dish containing the 

 solution; or, if heat is desired to intensify or hasten the proc- 

 ess, a watch-crystal holding the stain is placed over a Bun- 

 sen burner and in it the cover-glass; the cover-glass may be 

 held directly in the flame with the staining fluid upon it, 

 which must be constantly renewed until the process is com- 

 pleted, or the cover-glass can be heated in a test-tube, con- 

 taining stain solution. 



Removing Excess of Stain. The surplus stain is washed 

 off by dipping the glass in distilled water. 



Fig. 13. Author's bent forceps for holding cover-glass over flame. 



The water is removed by drying between filter-paper or 

 simply allowed to run off by standing the cover-glass slant- 

 wise against an object. When the specimen is to be examined 

 in water (which is always best with the first preparation of 

 the specimen, as the Canada balsam destroys to some extent 

 the natural appearance of the bacteria), a small drop of ster- 

 ilized water is placed upon the glass slide, and the cover-glass 

 dropped gently down upon it, so that the cover-glass remains 

 adherent to the slide. 



The dry system or the oil immersion can now be used. 



When the object has been sufficiently examined, it can be 

 permanently mounted by lifting the cover-glass off the slide 

 (this is facilitated by letting a little water flow under it, one 



