MAKING COVER-GLASS PREPARATIONS 25 



Cover-glass preparations of bacteria are permanently mounted 

 in the same manner as similar preparations made from the 

 blood or other tissues in histology, the process being to put a 

 drop of balsam on the center of the slide and place the prep- 

 aration, film downward, over it and apply slight pressure. 

 Label the preparation, giving the name of the organism, its 

 source (kind of culture, tissue, etc., from which the preparation 

 was made), stain used, and date. If the specimen is not pre- 

 served, the slide and cover glass should be cleaned for future use. 



35. Suggestions concerning the microscopic examination of 

 stained preparations of bacteria. In the examination of the 

 bacteria in the stained condition the following points, and 

 perhaps others, should be observed and noted, (a) Concern- 

 ing their morphology. Are they spherical, rod-shaped, or 

 spiral ? Are they separated or united in clumps or chains ? If 

 rod-shaped, are the ends pointed, round, or square? Are the 

 bacteria all of the same form and size? Note the presence 

 or absence of spores, granules, and capsules, (b) Concerning 

 their reaction to staining fluids. Do they stain uniformly or 

 irregularly? Do they stain deeply or faintly? Is the center 

 lighter than the periphery? Are there an unstained central 

 band and deeply stained ends (polar stain)? Do all of the 

 bacteria take the stain alike? 



36. Staining solutions. The basic aniline dyes are used in 

 staining bacteria. There is a large number of these, and there 

 are several formulae for preparing staining solutions from 

 each. Further, as will be seen from the chapters on staining 

 bacteria in the text-books, there are several methods of apply- 

 ing these stains. In an introductory course, however, it is 

 impossible to try them all, and consequently only those are 

 described which seem to be the best adapted for general use. 



In addition to the ordinary staining solutions and methods 

 there are special processes for certain species, such, for exam- 

 ple, as the tubercle bacterium, and still others for staining 

 certain parts of many bacteria, such as the flagella on motile 



