3,8 



BACTERIOLOGY 



Bacteria may be placed upon the cover-glass by allowing the 

 glass to fall upon one of the colonies of bacteria, on a gelatin or 

 agar plate (see page no), which will adhere to it in part, produc- 

 ing an "impression preparation" (German, Klatschpreparat) . 

 Such a preparation, after drying in the air, is to be fixed by pass- 



FiG. 23. — Cornet forceps for cover-glasses. 



ing it through the flame three times. (See below). The forceps 

 with which it is handled should be sterilized in the flame. 



Generally bacteria contained in fluids, like sputum, or taken 

 from the surface of a culture, are smeared over the cover-glass 

 by means of the platinum wire or loop, which must be heated to 



Pig. 24. — Stewart forceps for cover-glass. 



a red heat before and after the operation. Such preparations 

 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. Begiflners generally take too much 



Pig. 2S- — Novy's cover-glass forceps with clasp. {After Novy.) 



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 by holding the forceps with the 

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



