EXAMPLE 9 



Demonstration of Tubercle Bacilli in Sputum by 

 the Technique of Neelsen 



When Neelsen published his original technique for the demonstration 

 of tubercle bacilli, the standard magenta solution used for the staining of 

 bacteria was that proposed in the previous year by Ziehl. As a result, 

 Neelsen's technique was referred to as a modification of Ziehl, and to this 

 day the hyphenated tenn "Ziehl-Neelsen" is applied to almost any method 

 for the demonstration of tubercle bacilli in sputum regardless of the 

 author of the technique. 



It is proposed here to describe the original technique of Neelsen, leav- 

 ing it to the technician to determine which of the many other methods 

 given in Gray's "Microtomist's Formulary and Guide" can be more readily 

 applicable to his problem. It may be said in favor of the technique of 

 Neelsen that it gives a far better differentiation of tubercle bacilli than 

 do some of the more recent methods which, although they give good 

 preparations, tend to cause certain errors of diagnosis through the ability 

 of other bacteria to withstand the lower concentration of acids employed. 



It is to be presumed that the sputum collected from the patient will 

 have been placed at the disposal of the technician in the glass vessel in 

 which it was secured. It should be examined to see whether or not any 

 small yellowish particles exist in it, and if they do, one of these particles 

 should be extracted carefully with a sterile bacteriological wire loop and 

 utilized for the preparation. Even if no such particles are visible to the 

 naked eye, it is possible that tubercle bacilli will be present, but due con- 

 sideration should be given to some method of concentrating these bacilli 

 before making the smear. The standard method of concentration is to 

 hydrolyze the sputum to the extent necessary with the aid of a weak solu- 

 tion of potassium hypochlorite, which is known to be without action on 

 tubercle bacilli. For a long time a proprietary compound known as anti- 

 formin, which is a strongly alkaline solution of sodium hypochlorite, has 



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