326 MEDICAL BACTERIOLOGY 



EXERCISE 101. EXAMINATION OF SPUTUM. 



DEFINITION. By this term is meant all of the material derived 

 from the air passages by the act of coughing or hawking. 



METHOD OF COLLECTION. For diagnostic purposes it is best col- 

 lected in a salt-mouthed bottle (about 2 oz. capacity) which has been 

 sterilized. The morning sputum is best, and, before being collected, 

 the mouth should be rinsed out with water. 



ORGANISMS MOST COMMONLY FOUND. 



Bacterium tuberculosis. Place the sputum in a Petri dish over a 

 black surface and select one of the little cheesy masses, if these be 

 present, and smear it on a cover-glass. Where these particles are 

 not present a loop or two of the thick portion is used. The cover- 

 glass preparations are to be stained by one of the following methods : 



a. Gabbett, see Part 1, p. 62. 



&. Ziehl-Neelsen : 



1. Carbol-fuchsin ten times through the flame (5 to 10 min.). 



2. Nitric acid (30%) momentarily. 1 



3. Water. 



4. Alcohol (60%) until red color disappears. It may be 

 necessary to immerse preparation in acid a second time, but care 

 must be exercised to prevent extraction of dye from tubercle bac- 

 terium. 



5. Loeffler's methylen blue, 1 minute. 



6. Mount and examine. 



While the tubercle bacteria may be detected when present in 

 considerable numbers with a 1-6-inch objective, when there are few 

 present, a ^-inch oil immersion will be necessary, and this ought to 

 be used to search all slides where the tubercle germ has not been 

 found with a lower power. A mechanical stage is a great conven- 

 ience in a systematic search. 



At least two preparations should be stained and thoroughly exam- 

 ined before a negative result is pronounced. 



The viscosity of sputa may be overcome and the bacteria con- 

 centrated, where the number is very small, by 1) Ribbert's method 

 which consists in the addition of a 2% solution of caustic potash and 

 boiling. This dissolves the mucus, and the bacteria are then de- 

 posited with the sediment. This sediment can be obtained by allow- 



1 Eavenel recommends use of 5% nitric acid in 80% alcohol, claiming that 

 there is no danger of decolorizing the tubercle bacilllus no matter how long 

 the contact. 



