TUBERCULAR SPUTUM. 33 



This method is shorter but it' has not proven so 

 accurate, nor does it give as clear a film as the Ziehl- 

 Neelsen process. 



5. Staining in sudan III. 



(a) Place the prepared films in sudan III for 5 

 minutes. 



(6) Wash for 5 minutes in 70% alcohol. 



(c) Wash in water and then dry. 



(d) Counterstain for 1 minute in Loeffler's methy- 

 lene blue. Wash in water, dry and mount in the usual 

 manner. 



Examination of Sputum or Fluids containing 

 but few Tubercle Bacilli. 



When Tubercle bacilli are suspected but cannot be 

 demonstrated by ordinary examinations, several methods 

 may be adopted for further microscopic investigation. 



(a) Van Ketel's method. Add to the sputum about 

 three or four times its volume of 5% carbolic acid. If 

 the sputum is watery, add pure carbolic acid to make 

 a 5% solution. This is particularly applicable when 

 examining urine. Shake the mixture thoroughly, for 

 at least five minutes, to break up sputum particles. 

 Pour into a conical urine glass and allow to stand 12 to 

 24 hours. With a pipette, withdraw the lowest portion 

 of sediment for examination by any of the methods 

 already given. Films must be cleared in the alcohol- 

 ether mixture, before staining. 



(b) A more rapid method is to add to the sputum 

 sufficient 10% caustic potash solution, to liquefy it. 



