INTRODUCTION 7 



(4) Hold the cover-glass with Cornet forceps (Fig. 4) and 

 fix the bacteria by passing the glass, bacteria side up, three times 

 through Bunsen flame. In doing this the hand should describe 

 a circle about one foot in diameter, at the rate of once round 

 every second, the path of the glass passing through the flame. 



(5) Place the cover-glass, bacteria side down, on the surface 

 of the watery solution in the watch-glass (2), and allow it to 

 remain there for three to five minutes, during which time the 

 bacteria will become stained. Wash it in water and dry between 

 filter paper. 



(6) Clean the side of the cover-glass on which there are no 

 bacteria, and place it on a drop of water on a clean slide. 

 Examine and make drawings of the stained bacteria. 



FIG. 4. Cornet spring forceps. 



(7) If not sufficiently stained, float off the cover-glass with 

 water and stain again ; re-examine it after washing with water, 

 and, if satisfactory, dry it again between filter paper and leave 

 it in a warm place until all traces of moisture are gone ; then 

 mount it permanently in a drop of xylol balsam (Canada balsam 

 dissolved in xylol). 



Ex. 6. Prepare a solution of methylene blue in alcohol in 

 the same manner as the gentian violet solution in Ex. 5, 

 using : 



Methylene blue ... . . . 4 gr. 



Absolute alcohol . . . . . 50 c.c. 

 Label it and store in a stoppered bottle. Try its staining power 

 upon cover-slip preparations obtained as in Ex. 5 (3). 



