Il8 PHARMACEUTICAL BACTERIOLOGY 



b. By means of the platinum needle, spread a bit of the bacterial 

 growth or culture over the greater portion of the surface of the cover-glass. 

 Add a droplet of water, if desired, to separate the bacteria more. Spread 

 evenly. Do not use too much material, as it will make an unsightly 

 mount. 



c. Air-dry the smear preparation. This requires but little time, per- 

 haps a minute or two. 



d. Pass the cover-glass preparation through the flame of a Bunsen 

 burner four times. This must not be done too slowly as that will char or 

 burn the microbes, nor yet too quickly, as that would not coagulate the 

 albuminous matter and thus fail to fix the microbes upon the cover-glass. 

 A little experience will soon teach the proper speed. Four seconds, or a 

 little less, is the average time in which to make the four passages through 

 the flame. 



e. Place a drop or two of the stain on the fixed smear and allow it to 

 act long enough to stain sufficiently, holding the cover-glass over a flame to 

 warm the preparation. Do not heat it more than 60 to 70 C. On an 

 average the stain will be sufficiently deep in five minutes. Fuchsin re- 

 quires longer time than does methyl-blue or gentian-violet. 



f . Wash off the excess of the stain under a small hydrant stream or by 

 means of a wash bottle, or by moving it about in a dish of water. 



g. After washing, the preparation may be examined as a temporary 

 water mount. If it is satisfactory it may be made a permanent mount by 

 turning the cover-glass up again and allowing the water to evaporate and 

 then mounting in Canada balsam with xylene, oil of cloves or some other 

 diluent for Canada balsam. Oil of cloves acts on the stain for which 

 reason xylene, benzene or some other balsam diluent of the coal-tar series 

 is preferable. Special staining methods have already been explained. 

 The above is a general method which will serve most purposes. It should 

 be kept in mind that the staining process shrinks the microbes somewhat. 

 The ordinary staining methods do not bring out the cilia. The fact that 

 the microbe is motile is evidence that cilia are present, though it cannot 

 be known whether they are unipolar, bipolar or general, single or multiple. 



