Staining of bacterial flagella

Flagella staining is generally considered a rather difficult pro-cedure and even with the most careful technique only a few of a great number of slides show satisfactory flagella. The main trouble with most flagella stains is that the mordant which is used is not stable. Good results may be obtained at one time and poor results the next. An important property of a good flagella stain should, then, be a stable mordant. Such a mordant was described by Gray (1). He mixed potassium alum, mercuric chloride, tannic acid, and alcoholic fuchsin and immediately poured the mixture on the smear. All these reagents are per-fectly stable and the stain can always be duplicated. It is excel-lent as compared with other flagella stains. A counter stain of a strong solution of basic fuchsin is also necessary. This stain gives most excellent results with the sporulating organisms such as B. vulgatus, B. subtilis, B. terminalis, Cl. botulinum, Cl. tetani, etc. With Bact. typhosum, and the Vibrios, not so good results are obtained. Various modifications of the stain were tried. A distinct improvement was the addition of sufficient hydrochloric acid to the alum to make the concentration of acid 1/100 N. Ammonium alum in place of potassium alum was found to give fully a good result. However, it was not until addition of alcohol was tried that an almost perfect flagella stain was ob-tained. Without the alcohol in the so-called "mordant, " the flagella can be seen very faintly without the counter stain. Wit