EXAMINATION OF BACTERIA WITH THE MICROSCOPE. ^^ 



and milk and its products quite often contain other acid-proof 

 bacilli. The smegma of the external genitals also frequently 

 contains acid-proof baciUi 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. (See smegma bacilU in 

 Part II., Chapter IV.) 



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 con- 

 taining tubercle bacilli. Often Kttle white particles may be 

 seen floating in the mucous portions of the sputum. These 

 particles should be selected for the investigation, and may be 

 spread in a thin film on the cover-glass with the platinum wire, 

 which is steriHzed in the flame before and after using. The 

 selection of the little white particles will be facilitated if the 

 sputum be poured into a clean glass dish, which may be placed 

 on a black surface. A form of porcelain dish is furnished by 

 dealers, the bottom of which is black, and which is convenient, 

 for these manipulations. The smears must be made thin, or the 

 subsequent decolorization, after staining, will not be uniform. 

 It is hardly necessary to observe that the operator must be 

 scrupulously careful not to contaminate the material under 

 examination with any kind of extraneous matter. The cover- 

 glasses and sHdes which are used should be new, and should 

 have been cleaned with bichromate of potassium and sulphuric 

 acid (see page 25). 



When the work is completed, the bottle containing the 

 sputum should be steriHzed by steam or boiling. 



Many different methods for staiaing the tubercle bacillus 



