150 



BACTERIOLOGY. 



The color can be forced into the specimen, thus making 

 it stand out more sharply than would otherwise be the case, 

 by holding the glass-slip, covered with the dye, over a low 

 Bunsen, or alcohol flame till vapors begin to rise. The 

 specimen is then washed as before. 



Instead of heating the dye on the cover-glass, it may be 

 heated before use. For this purpose the bottle of dye is 

 placed on an iron plate, and this is heated by a low flame. 

 Pig. 22 shows such an iron plate, as used in the author's 

 laboratory, slipped under the flange of the ordinary water- 

 bath. This plate is 3.5 mm. thick, 7.5 cm. wide, and 15 

 cm. long. 



Fig, 22. Water-bath with iron plate for heating dyes, cover- 

 glassses, etc. 



When it is desirable to preserve a stained specimen, this 

 should be floated off the slide by the addition of a drop, or 

 two, of water to the edge of the cover-glass. If cedar oil 

 has been used it should be carefully removed by rotating 

 the cover-glass on a piece of filter paper. The preparation 

 should then be placed, specimen side turned up, under a 

 watch-glass until perfectly dry. Or, the drying may be 



