160 PATHOGENIC BACTERIA. 



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 1 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 

 covered with the hot stain is laid aside for a minute, then 

 washed in water and mounted. In such preparations I 

 have always been able to see the flagella well, but usually 

 find that while the flagella are very distinct, the bodies 

 of the bacteria are scarcely visible. 



Bunge suggests a mordant consisting of a concentrated 

 aqueous tannin solution and a i : 20 solution of liq. ferri 

 sesquichloridi in water. The best mixture seems to be 

 3 parts of the tannin solution to 1 part of the diluted 

 iron solution. To 10 c.cm. of this mixture 1 c.cm. of a 

 concentrated aqueous fuchsin solution is added. It is 

 not necessary to prepare this mordant fresh for each 



1 Med. News, Sept. 7, 1895. 



