26 



MANUAL OF BACTERIOLOGY. 



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 a red heat before and after the operation. Such prepara- 



FIG. 7. Cornet forceps for cover-glasses. 



tions are called smear, cover-glass, cover-slip, or film prep- 

 arations. 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 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 hold- 



FIG. 8. Stewart forceps for cover-glasses. 



ing 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 the preparation, it is to be passed 

 with the smeared surface up three times through the flame of 

 a Bunsen burner or alcohol lamp. This should not be done too 

 slowly and yet sufficiently so to fix the preparation. Various 

 directions are given by different authors as to the time which 



