CHAPTER X. 



Methods of Staining — Cover-slip Preparations — Impression Cover-slip 

 Preparations — Solutions Employed — Preparation and Staining of 

 Cover-slips — Staining Solutions — Special Staining Methods. 



A COMPLETE list of solutions and methods that are 

 recommended for the staining of bacteria is not essential 

 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 bacteria stain best with 

 watery solutions of the basic aniline 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 dimen- 

 sions, require to be more conspicuously stained than the 

 surrounding materials upon the cover-slips or in the sec- 

 tions, otherwise their recognition is a matter of the greatest 

 difiiculty, if not of impossibility. For this reason, especially 

 in section-staining, it frequently becomes 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 bacteria, constantly in use in these 

 studies, is performed in the following way: 

 (158) 



