THE STAINING OF FLAGELLA. 319 



solutions are then added and the liquid is filtered at once. A volu- 

 minous precipitate must remain on the filter, otherwise the mordant 

 is useless. The mordant can be used at once, and will keep for six 

 weeks or more. It should be kept in the dark. The mordant is said 

 to give excellent results with all motile bacteria. 



The stain employed is made by adding 4 to 5 g. of fuch- 

 sin to 100 c.c. of anilin water, to which 1 c.c. of a 1 per 

 cent. NaOH solution has been added. Hot, freshly pre- 

 pared carbolic fuchsin, or an aqueous 1 per cent, solution 

 of fuchsin, may be used. Both mordant and stain should 

 be kept warm while in use. The iron plate shown in Fig". 

 22 (p. 150), will be found useful for this purpose. 



Giant- wJdps. — These interesting forms are especially 

 abundant in the few drops of condensation water 

 which accumulate at the bottom of the freshly inclined 

 agar. They are met with under these conditions in 

 cultures of most of the known motile bacteria. Owing to 

 their extremely large size they can readily be seen in the 

 hanging-drop. The author's method is to place on a cover- 

 glass a drop of blood-serum, which is then inoculated with 

 the turbid liquid mentioned. In about 15 minutes, more or 

 less agglutination of the bacteria results and the large 

 spiral bodies are then plainly visible. They may be broad, 

 spindle-shaped, or very long, slender, wavy lines. They 

 have been observed to exceed 100 ,« (sis inch) in length (see 

 p. 38). 



