104 CLINICAL BACTERIOLOGY. 



the staining power of these substances may be increased 

 considerably. Among substances to be mentioned in this 

 connection are : 



1. Potassium hydroxid (employed by Loffler in combina- 

 tion with methylene-blue) : 



30 cu. cm. of concentrated alcoholic solution of methylene-blue. 

 100 cu. cm. of o.oi per cent, solution of potassium hydroxid (i : 10,000). 



This so-called Loffler's solution stains well, and may be 

 preserved for an almost indefinite time. 



2. Aniline water : 



Four or 5 cu. cm. of aniline oil, with 100 cu. cm. of dis- 

 tilled water (i part of aniline oil to about 20 parts of 

 water), are vigorously shaken and passed through a moist- 

 ened filter. To the clear filtered aniline water (100 cu. cm.) 

 are added n cu. cm. of a concentrated alcoholic solution 

 of fuchsin or of gentian-violet or methyl-violet. It is more 

 convenient to filter the aniline water in a watch-glass and to 

 add the solution of fuchsin or gentian-violet or methyl- 

 violet until a metallic, opalescent pellicle appears upon the 

 surface. These solutions of Ehrlich stain well, but they 

 possess the disadvantage that they decompose rapidly, and 

 they must, therefore, be freshly prepared each time that 

 they are used. 



3. Carbolic acid : 



One gram of fuchsin is dissolved in 10 cu. cm. of 96 per 

 cent, alcohol, and then 90 cu. cm. of 5 per cent, carbolic 

 acid are added. 



This solution of Ziehl does not possess quite so intense a 

 staining power as the aniline-water solutions, but it has over 

 these the not inconsiderable advantage of greater durability. 

 In an analogous manner carbolic-acid gentian-violet, and 

 carbolic-acid methylene-blue solutions are prepared, both 

 of which possess excellent staining qualities, and can be 

 preserved for a long time. 



Preparation and Staining of Cover-glass Specimens. 

 In making stained preparations the suspected material is 

 spread in as thin a layer as possible upon a cover-glass 

 thoroughly cleansed with alcohol and dried, a small drop 

 being taken, by means of the platinum loop, directly from 

 liquid cultures not more than one or two days old, or a 

 small amount of the bacterial mass from solid cultures being 

 rubbed up in a drop of sterilized water (or tap-water, which 



