BACTERIOLOGY 



are called smear, cover-glass, cover-slip, or film preparations. 

 When the material to be spread is thick or very viscid, a small 

 drop of distilled water must first be placed in the center of the 

 cover-glass so as to dilute it. Beginners generally take too much 



FIG. 23. Cornet forceps for cover-glasses. 



material on the wire. As thin a smear as possible is made. It 

 is allowed to dry in the air; this should occupy a few seconds. 

 The drying may be hastened 4 by holding the forceps with the 

 cover-glass a long distance above the flame, at a point where 

 the heat would cause no discomfort to the hand. Having dried 



FIG. 24. Stewart forceps for cover-glass. 



the preparation, it is to be passed through the flames of a Bunsen 

 burner or alcohol lamp three times, taking about one second for 

 each transit. The heat of the flame serves to dry the bacteria 

 upon the cover-glass and fix them permanently in position; it is 

 not sufficient, however, when applied in this manner, to kill all 



FIG. 25. Novy's cover-glass forceps withe clasp. (After Novy.) 



kinds of bacteria, especially those containing spores. After it 

 has been passed through the flame three times the preparation 

 may be stained with one of the aniline dyes, and after washing 

 in water and drying, may be mounted, face down, in Canada 



