30 ESSENTIALS OF BACTERIOLOGY. 



Spores, automatic movements, fission, and cultivation in 

 general can be studied for several days. This moixt chmnlur 

 can be placed in a brood-oven or on the ordinary warming 

 stages of the microscope. 



CHAPTER IY. 



STAINING OF BACTERIA. 



STAINING or coloring bacteria is done in order to make them 

 prominent, and to obtain permanent specimens. It is also 

 necessary to bring out the structure of the bacteria, and 

 serves in many instances as a means of diagnosis ; and lastly, 

 it would be well-nigh impossible to discover'them in the tissues, 

 without staining. 



Only since the aniline colors bave come into active use, has 

 the technology of staining become developed. 



Aniline Colors. Of the numerous dyes in the market, nearly 

 all have, at one time or other, been used in staining bacteria. 

 But now only a very few find general use, and with methyline 

 blue and fuchsin nearly every object can be accomplished. 



Basic and Acid Dyes. Ehrlich was the first to divide the 

 aniline dyes into two groups, the basic colors to which belong 

 Gentian violet, 

 Methyl violet, 

 Methylin blue, 

 Fuchsin, 

 Bismark-brown, 

 And the acid colors to which eosin belongs. 



The basic dyes stain the bacteria and the nuclei of cells ; the 

 acid dyes stain chiefly the tissue, leaving the bacteria almost 

 untouched. Carmine and Hcematoxylin are also useful as con- 

 trast stains, affecting bacteria very slightly. The aniline dyes 

 are soluble in alcohol or water or a mixture of the two. 



Staining Solutions. A saturated solution of the dye is made 

 with alcohol. This is called the stock or concentrated solution ; 



