CHAPTER X. 



Methods of staining Cover-slip preparations Impression cover- 

 slip preparations Solutions employed Preparation and stain- 

 ing of cover-slipsStaining solutions Special staining 

 methods. 



A COMPLETE list of solutions and methods that are 

 recommended for the staining of bacteria is not essen- 

 tial to the work of the beginner, so that only those 

 which are of the most common application will be given 

 in this book. In general, it suffices to say that bac- 

 teria stain best with watery solutions of the basic ani- 

 line dyes, and of these, fuchsin, gentian- violet, and 

 methylene-blue are those most frequently employed. 



In practical work bacteria are either dried upon cover- 

 slips and then stained, or stained in sections of tissues in 

 which they have been deposited during the course of 

 disease. In both processes the essential point to be borne 

 in mind is that the bacteria, because of their microscopic 

 dimensions, require to be more conspicuously stained 

 than the surrounding materials upon the cover-slips or 

 in the sections, otherwise their recognition is a matter of 

 the greatest difficulty, if not of impossibility. For this 

 reason, especially in section-staining, it frequently be- 

 comes necessary to decolorize the tissues after removing 

 them from the staining-solutions, in order to render the 

 bacteria more prominent, and for this purpose special 

 methods, which provide for decolorization of the tissues 

 without robbing the bacteria of their color, are employed. 

 The ordinary method of cover-slip examination of bac- 



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