78 MICROSCOPICAL EXAMINATION OF BACTERIA 



4. Hold the slide firmly on the bench with the thumb 

 and forefinger of the left hand applied to the end 

 nearest the drop of fluid. 



5. Take another clean 3 by i slide in the right hand 

 and lower its short end obliquely (at an angle of about 

 60) transversely on to the mixed ink and culture en 

 the first slide, and allow the fluid to spread across the 

 slide and fill the angle of incidence. 



6. Maintaining the original angle, draw the second 

 slide firmly and evenly along the first toward the end 

 farthest from the left hand (Fig. 69, Z>). 



7. Throw the second slide into a pot of disinfectant; 

 allow the first slide to dry in the air. 



FIG. 69. Spreading negative film. 



8. Place a drop of immersion oil on the centre of the 

 film, lower the i/i 2-inch objective into the oil and 

 examine microscopically without the intervention of 

 a cover-slip. 



(The film of ink may be covered with a long cover- 

 glass and xylol balsam as a permanent preparation.) 



(b) Hanging-drop Preparation. 



1. Smear a layer of sterile vaseline on the upper 

 surface of the ring cell of a hanging-drop slide by means 

 of the glass rod provided with the vaseline bottle, and 

 place the slide on a piece of filter paper. 



2. "Flame" a cover-slip and place it on the filter 

 paper by the side of the hanging-drop slide. 



3 . Place a drop of water on the centre of the cover- 

 slip by means of the platinum loop. 



