THE BACILLUS OF TUBERCULOSIS 311 



lent, cheesy, and mucopurulent sputum usually contains bacilli; while 

 pure mucus, blood, and saliva, as a rule, do not. When hemorrhage 

 has occurred, if possible, some purulent, cheesy, or mucopurulent sputum 

 should be collected for examination. The sputum should not be kept 

 any longer than necessary before examination, for, though a slight 

 delay or even till putrefaction begins, does not vitiate the result so far 

 as the examination for tubercle bacilli is concerned, it almost destroys 

 any proper investigation of the mixed infection present; it is best, there- 

 fore, to examine it in as fresh a condition as possible, and it should be 

 kept on ice until examined if cultures are to be made. 



2. METHODS OF EXAMINATION. Examination for Tubercle Bacilli. 

 Pour the specimen into a clean, shallow vessel, having a blackened 

 bottom a Petri dish placed upon a sheet of dull black paper answers 

 the purpose and select from the sputum some of the true expectora- 

 tion, containing, if possible, one of the small white or yellowish-white 

 cheesy masses or " balls" which it contains. From this make rather 

 thick cover-glass or slide "smears" in the usual way. In doubtful 

 cases a number of these coarse or fine particles should be placed on 

 the slide. The material being thick, should be evenly spread and very 

 thoroughly dried in the air before heating. Immerse this in a solution of 

 Ehrlich's aniline-water fuchsin, contained in a thin watch-glass or porce- 

 lain dish, and steam over a small flame for two minutes. Then remove 

 the glass from this and wash with water. Now decolorize by immersing 

 the stained preparation in a 3 per cent, hydrochloric acid solution in 

 alcohol for from one-half up to one minute, removing at the time when 

 all color is just about gone from the cover-glass smear. Wash thor- 

 oughly with water, and make a contrast stain by applying a cold solu- 

 tion of Loeffler's alkaline methylene blue- 

 Concentrated alcoholic solution of methylene blue . . 30 c.c. 

 Caustic potash (1:10,000 solution) 100 " 



for from fifteen to thirty seconds. Wash with water; press between 

 folds of filter paper; dry in the air; mount and examine. 



The tubercle bacilli are distinguished by the fact that they retain 

 the red color imparted to them in the fuchsin solution, while the other 

 bacteria present, having been decolorized in the acid solution, take 

 the contrast stain and appear blue. (See Plate L, Figs. 1 and 2.) 



Various methods have been suggested for the staining of tubercle 

 bacilli, but the original method as employed by Koch, or some slight 

 modification of it, is so satisfactory in its results that it seems unneces- 

 sary to substitute others for it. The above is a slight modification of 

 the Koch-Ehrlich method, differing from it chiefly in the use of a weak 

 for a strong acid decolorizer. It has been found that the strong acid 

 solution originally employed (5 per cent, sulphuric acid solution in 

 alcohol) often decolorizes some of the bacilli entirely by its too energetic 

 action, and that a weaker decolorizer, such as the above, gives more 

 uniform results. 



