162 



PUBLIC HEALTH BACTERIOLOGY 



(should dry at once). Fix by passing three times through 

 the flame. Stain for two or three minutes. Wash with 

 water and examine on clean slide in water-drop (using oil 

 immersion). In water-drop bacteria look larger, can be 

 restained, and can be kept longer than when mounted 

 direct in Canada balsam. To preserve : allow to dry, 

 remove from slide, roll up, and label. 



Counterstain with eosin or other stain in dilute solution 

 for I to 2 minutes. Eosin stains cell protoplasm red. 



Films are also made on slides, which are more easily 

 handled than coverslips. 



Gram's Method of Staining Depends on the fact 

 that some bacteria when well stained retain the stain after 

 treatment with a solution of iodine and subsequent washing 

 with alcohol (strong or absolute). This is believed to be 

 due to the stain and the iodine forming a combination 

 which resists decoloration. 



TABLE. 



Gram-positive 



Gram-negative 



(Retain the gentian-violet) 

 Staphylococcus pyogenes 

 Streptococcus ,, 



Pneumococcus 

 Micrococcus tetragenus 

 Bacillus anthracis 



,, subtilis 



diphtherias 



,, tetani 



,, botulinus 



tuberculosis and 

 other acid-fasts 



,, aerogenes capsu- 

 latus 



,, enteritidis sporo- 

 genes 



,, of swine erysipelas 



,, of mouse septi- 



,, caemia 



,, of potato 

 Yeasts and many moulds 

 Streptothrix actinomyces 



(Take the counter stain} 

 Meningococcus 

 Gonococcus 

 Micrococcus melitensis 

 catarrhalis 



Colon-typhoid group of bacilli 

 Cholera group of spirilla 

 Bacillus pestis and group 



mallei 



influenzae 



pyocyaneus 



proteus 



Koch-Weeks 



Morax-Axenfeld 



maligni cedematis 



anthracis symptomatic! 



of fowl cholera 



of rabbit septicaemia 

 Spirillum Obermeieri (spirochaete) 

 Friedlaender's diplobacillus 



METHOD. Stain for 5 minutes with aniline-oil-gentian- 

 violet, or carbol-gentian-violet. Pour off excess of stain 



