METHODS OF OBSERVING BACTERIA. 103 



will appear. Loffler has fortunately worked out the 

 amounts required for some of the species, and of the 

 more important ones the following amounts of Solutions 

 B and C must be added to 16 c.cm. of Solution A to 

 attain the desired effect : 



Cholera spirillum, ^-i drop of Solution C ; 



Typhoid fever, i c.cm. of Solution B ; 



Bacillus subtilis, 28-30 drops of Solution B ; 



Bacillus of malignant edema, 36-37 drops of Solution B. 



Part of the success of the staining depends upon 

 having the bacteria thinly spread upon the glass, and as 

 free from albuminous and gelatinous materials as possi- 

 ble. The cover-glass must be cleaned most painstakingly : 

 too much heating in fixing must be avoided. After using 

 and washing off the mordant, the preparation should be 

 dried before the application of the anilin-water-fuchsin 

 solution. 



Pitfield l has devised a simple and good method of 

 staining flagella. A single solution at once mordant and 

 stain is employed. It is made in two parts, which are 

 filtered and mixed. 



A. Saturated aqueous solution of alum, 10 c.cm. ; 

 Saturated alcoholic solution of gentian-violet, i c.cm. 



B. Tannic acid, i gr. ; 

 Distilled water, 10 c.cm. 



The solutions should be made with cold water, and 

 immediately after mixing the stain is ready for use. The 

 cover-slip is carefully cleaned, the grease being burned 

 off in a flame. After it has cooled the bacteria are 

 spread upon it, well diluted with water. After drying 

 thoroughly in the air, the stain is gradually poured on 

 and by gentle heating brought almost to a boil ; the slip 



1 Med. News, Sept. 7, 1895. 



