SPECIAL METHODS. 



TUBERCLE BACILLUS. 



Koch's Original Method. 



Sections or cover-glass preparations are placed in Koch's 

 Methylene Blue Solution (p. 58) and left in it for 20 to 24 

 hours, or J to 1 hour if warmed to 40C. (104F.) ; they are 

 then placed in aqueous solution of Vesuvine for 2 minutes ; 

 this removes the blue colour from the tissue, staining it 

 brown, while the bacilli remain blue ; the excess of colour is 

 washed out in Distilled Water ; if cover-glass preparations, 

 they are then dried and mounted in Balsam ; if sections, they 

 are dehydrated in Absolute Alcohol, cleared in Cedar Oil, 

 and mounted in Balsam. 



Kocli-Ehrlich Method. 



In G-entian- Violet Aniline- Water (p. 58), or Fuchsine 

 Aniline- Water (p. 59), place sections or cover-glass prepara- 

 tions for at least 12 hours (more rapid staining of the latter 

 is obtained by warming) ; then immerse in Nitric Acid (p. 

 62) for some seconds. Einse in 60 p. c. Alcohol for some 

 minutes, and then count erstain with Aqueous Solution of 

 Yesuvine (p. 38) after Violet, and with Aqueous Solution of 

 Methylene Blue (p. 36) after Fuchsine ; rinse in water, dehy- 

 drate, clear, and mount in Balsam. 



Nitric Acid is apt to injure delicate sections. To avoid this 



