CHAPTEE X. 



Methods of staining— Solutions employed— Preparation and staining of 

 cover-slips— Preparation of tissues for section-cutting— Staining of tissues- 

 Special staining methods. 



The entire list of solutions and methods that are 

 recommended for the staining of bacteria are not essen- 

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

 which are of most common application willbe given in 

 this book. In general, it suffices to say, 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 require to be stained in 

 two conditions.: 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 sections, otherwise their differentiation is a matter 

 of the greatest difficulty, if not of impossibility. For 

 this reason, especially in the case of 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 decolor- 

 ization of the tissues without robbing the bacteria of 



