88 BACTERIOLOGY 



A solution is prepared of 1 grm. Victoria blue in 50 

 c.cm. of alcohol diluted to half its strength, and this is again 

 diluted to the same exten with a half per cent, aqueous 

 solution of ammonium carbonate. Staining lasts from one to 

 five minutes, and the sections are decolorised in iodine and 

 potassium iodide, and further treated as directed by Gram, 

 except that instead of alcohol a solution of fluoresceine 

 (1 grm. fluoresceine to 50 c.cm. absolute alcohol) is used for 

 extracting the colouring matter. 



A further process consists in adding some hydrochloric 

 acid (1 drop to 50 grms. water) to a concentrated aqueous 

 solution of violet and using this to stain the sections, which 

 are otherwise treated as in Gram's method. 



In using carbolic methyl blue the sections are stained 

 for from half an hour to two hours, rinsed in water mixed 

 with hydrochloric acid, passed through a weak aqueous 

 solution of lithium carbonate, and transferred from that 

 to absolute alcohol and to aniline oil, in both of which a 

 little methyl blue has been dissolved. After rinsing in 

 pure aniline oil they are cleared in an etherial oil which is 

 then removed with xylol, and are mounted in Canada 

 balsam. 



Pragl recommends a modification of the carbolic methyl 

 blue method, which consists in staining the sections, fixed 

 to a slide or cover-glass, for from half to one minute in 

 carbolic methyl blue, after which they are rinsed in water 

 for a short time, decolorised in 50 per cent, alcohol, de- 

 hydrated in absolute alcohol, cleared in xylol, and mounted 

 in resin. 



Another method which is easily applied consists in stain- 

 ing the sections for three to five minutes in carbolic fuchsine, 

 rinsing in water, and passing through alcohol. They are 

 then laid for a quarter of an hour to two hours in aniline 

 oil containing some methyl green, in order to decolorise and 



