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EXAMINATION OF SPUTUM FOR THE TUBERCLE BACILLUS. 



Ziehl-Neelsen Method. A ]oopful of the sputum is 

 transferred to a wide cover-glass and thoroughly spread 

 over the surface. It is then allowed to dry in the air, or 

 by moving it to and fro over the flame, and then fixed in 

 the usual way. The cover-glass is held in the forceps, 

 specimen side up, and covered with carbolic fuchsine solu- 

 tion. It is warmed over the flame for 1 to 2 minutes, 

 avoiding actual ebullition, and then washed with water. 

 The specimen is now dipped in dilute nitric acid (a watch- 

 glass is filled with water and 3 or 4 drops of nitric acid 

 added), for a few seconds. Then transferred to dilute 

 alcohol (60 to 70X), where it is moved about till it is 

 almost decolored. After this it is washed with water and 

 stained for a few seconds with methylene blue. The lat- 

 ter is washed off with water and the specimen examined 

 under the microscope. It should show the tubercle bacil- 

 lus stained bright red, on a light blue back-ground. 



Heavily stained preparations can be obtained by 

 floating the prepared cover-glass on the carbolic-fuchsine 

 solution for 15 or 30 minutes, then decoloring, as before. 



Cover-glass preparation. 



Air-dried. 



3 x through flame. 



Carbolic-fuchsine, hot, (1 to 2 min.). 



Water. 



Dilute nitric acid (few seconds). 



Dilute alcohol. 



Water. 



Methylene blue (i to % min.). 



Water (and examine). 



Air-dried. 



Canada balsam. 



A 2 per cent, aqueous solution of anilin hydrochloride 

 can be used to excellent advantage instead of the dilute 

 nitric acid. 



