EXAMINATION FOR BACTERIA IN FILMS l6l 



methods should be reHed on, and the microscopic examination 

 should be regarded as a mere preliminary, enabling the observer 

 to see whether bacteria are present in enormous numbers or not. 

 The films are prepared and fixed in one or other of the methods 

 which will be described subsequently (see p. 218), the only point 

 worthy of notice being that the skin must be very thoroughly 

 cleansed ; it may be scrubbed with soap and a nail-brush, using 

 plenty of hot water. The films need not be very thin and even. 



The method of staining will depend upon the organism which 

 IS likely to be found, and more especially whether it stains by 

 Gram's method. This is so important in this connection that a 

 repetition of a previous table will not be out of place. 



Gram's Method. 

 Stained. Unstained. 



Streptococci. Typhoid bacilli. 



Staphylococci. Bacillus of glanders. 



Bacillus of anthrax. Bacillus of influenza. 



Bacillus of tubercle. Bacillus of plague. 



Pneumococcus. Bacillus coli. 



Spirillum of relapsing fever. 



Gonococcus. 



If the organism which is present appears in the first list, the 

 staining process is simply that which we have described previously, 

 and the organism will be stained dark blue or violet, and the other 

 structures will be unstained. 



If the bacteria which are present in the films do not stain by 

 Gram's method the matter is more difficult, for any stain which 

 colours them will colour the nuclei of the leucocytes also. Jenner's 

 stain may be used, or the film may be stained by eosin and methy- 

 lene blue separately. The organisms will then be stained blue. 

 Carbol thionin is even more suitable, as the colour which it 

 imparts to the nuclei of the leucocytes is not deep and the red 

 corpuscles are merely tinged. This is the stain which we recom- 

 mend for general use, and in cases in which the nature of the 

 organism (if one be presented) is entirely unknown. 



If bacteria are detected by any of these methods their nature 

 must be recognized by a consideration of their morphological 

 features and staining reactions. 



