MAKING COVER-GLASS PREPARATIONS 23 



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

 tion was made), stain used,- and date. If the specimen is 

 not preserved, the slide and cover-glass should be cleaned for 

 future use. 



33. 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, (i) 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 and capsules, (z) Concerning their reaction 

 to staining fluids. Do they stain uniformly or irregularly ? Do 

 they stain deeply or faintly? Is the centre lighter than the 

 periphery? Is there an unstained central band and deeply 

 stained ends (polar stain) ? Do all of the bacteria take the 

 stain alike? 



34. 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 im- 

 possible to try them all, and consequently 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 cer- 

 tain parts of many bacteria, such as the flagella on motile forms, 

 the spores in spore-bearing organisms, and the capsule on 

 certain other species. There is a large number of these 

 special methods, but in this course only one of each will be 

 given. These will be taken up in connection with the study of 

 the bacteria requiring them. 



