THE STAINING OF MICROORGANISMS 89 



8. Flood the entire specimen-side of the cover-glass 

 with stain, using a pipette. 



9. Allow the stain to act a short time. 



Note. The time required for staining varies so much with the 

 different stains, different organisms and their physiological conditions, 

 that no exact time can be given. In general, a good specimen is 

 obtained by staining one-half to one minute with fuchsin or gentian 

 violet, or one to five minutes with methylen blue. 



10. Wash the specimen in running water. 



11. Mount the cover-glass in water, specimen side 

 down, on a clean slide. 



12. Dry the upper surface of the cover-glass and take 

 up any excess of water by means of filter paper. 



13. Examine the slide under the microscope, using 

 objective No. 7 and ocular No. 1. 



14. If satisfactory, remove the cover-glass carefully 

 from the slide, floating it off if necessary. 



15. Allow it to dry in the air, specimen side up. 



16. Place a clean slide exactly on the figure (Fig. 32). 



17. Let a small drop of Canada balsam fall in the center 

 of the slide, marked by the circle. 



Note. The consistency of the Canada balsam should be like thin 

 cream. The diameter of the glass rod should not be more than 4 mm. 



18. Place the cover-glass, specimen side down, on this 

 drop. 



19. Allow the balsam to spread over the entire under 

 surface of the cover-glass (without pressing it down on the 

 slide) and keep the cover-glass straight, coinciding with the 

 lines of the figure. 



20. Label, stating in order, the name of the organism, 

 the age and kind of culture, the stain used, the date, your 

 own name and the purpose of the stain if otherwise than 

 ordinary, e.g., spore stain. 



21. Allow the slide to stand in a horizontal position for 

 a few days until the balsam becomes hard. 



