168 BACTERIOLOGY. 



more or less prolonged immersion in the fuchsin stain. 

 The potassium bichromate is washed out with water, 

 and the slides are then placed in a fuchsin stain, which 

 is prepared as follows : 



Fuchsin 1.5 grammes. 



Absolute alcohol 14 c.c. 



Carbolic acid crystals, pure . . . . . 6 grammes. 



Water 100 c.c. 



Dissolve the fuchsin in the alcohol and the carbolic 

 acid in the water. Mix the two solutions and let stand 

 for twelve hours, with occasional shaking or stirring, 

 then filter. 



The length of time that the slide remains in this solu- 

 tion varies with circumstances. The tubercle bacilli 

 stain very quickly ; in tissues properly hardened in 

 alcohol five minutes is generally sufficient to stain them 

 them deeply. 



Prolonged immersion in the fuchsin does no harm 

 and insures certainty of results. After a section has 

 been in the stain a sufficient length of time it, with the 

 slide to which it is cemented, is washed in water until 

 the surplus stain is removed ; it is then subjected to 

 the action of a combined decolorizer and contrast stain 

 made as follows : 



Methyl-blue 2. 25 grammes. 



Absolute alcohol 30 c.c. 



Sulphuric acid 12 " 



Water (distilled) 100 " 



Dissolve the methyl-blue in the alcohol, add the acid 

 to the water, mix the two solutions, and let stand, with 

 occasional shaking, for twelve hours, then filter. 



This solution is allowed to act upon the tissue for a 

 few seconds, and as soon as the blue color predominates 

 over the red, as seen by transmitted light, the section is 





