THE MICROSCOPE AND MICROSCOPIC METHODS 47 



Butter bacillus of Rabinowitsch, 



Certain strep to thrices, 



Certain bacilli common in the feces of cattle, 



Certain bacteria found in distilled water, 



Spores of many bacteria. 



Occasionally other bacteria, micrococci and horny epithelial 

 cells are imperfectly decolorized, but their forms distinguish 

 them from tubercle bacilli. Minute crystalline needles which 

 have a shape like that of bacilli, are often encountered in sputum, 

 but their nature will be recognized after a little practice. 



The stain for acid-proof bacteria is most frequently used for 

 specimens of sputum from cases of suspected pulmonary tubercu- 

 losis; it may be applied to other fluids and secretions equally 

 well. It is not reliable, however, when applied to milk, as the 

 oil present in milk interferes with its operation, and milk 

 and its products quite often contain other acid-proof bacilli. 

 The smegma of the external genitals also frequently contains 

 acid-proof bacilli that are not tubercle bacilli. On this account 

 all fluids and discharges from the genito-urinary tract need to 

 be examined with particular care not to confuse tubercle bacilli 

 with smegma bacilli. Too much reliance should not be placed 

 on the possibility of distinguishing between tubercle and smegma 

 bacilli by decolorizing in alcohol. In doubtful cases an animal 

 should be inoculated. 



Patients should be given minute instructions concerning the 

 collection of sputum. The bottle used should be new, wide- 

 mouthed, clean, and kept tightly stoppered with a clean cork. 

 The patient should be cautioned against allowing the expectora- 

 tion to get on the outside of the bottle. Probably whatever 

 risk is incurred by those who examine sputum comes chiefly 

 from the outside of the bottle having been soiled with sputum 

 containing tubercle bacilli. It is well to disinfect the exterior 

 of the bottle when it is received at the laboratory. Often little 

 white particles may be seen floating in the mucous portions of 

 the sputum. These particles should be selected for the investiga- 



