27 



mounted in the same manner as similar preparations made 

 from the blood or other tissues in histology, the process be- 

 ing to place a drop of the balsam on the center of the slide 

 and place the preparation, 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 preserved the slide and cover-glass 

 should be cleaned for future use. 



§ 30. Suggestions concerning the microscopic exam- 

 ination of stained preparations of bacteria. In the ex- 

 amination of the bacteria in the stained condition the fol- 

 lowing points, and perhaps, others should be observed and 

 noted, (i) Concerning their morphology. Are they spher- 

 ical, 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. 

 (2) 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 ? Is there 

 an unstained central band and deeply stained ends (polar 

 stain) ? Do all of the bacteria take the stain alike? 



§ 31. 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 solu- 

 tions from each. Further, as will be seen from the chapters 

 on staining bacteria in the text-books, there are several 

 methods of applying these stains. In an introductory course, 

 however, it is impossible to try them all and consequently 

 those are described which seem to be the best adapted for 

 general u.se. 



In addition to the ordinary staining solutions and methods 

 there are special processes for certain species such, for 

 example, as the tubercle bacillus, and still others for stain- 



