CHAPTER 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 is not essen- 

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

 which are of 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 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 fre- 

 quently 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 



