104 PATHOGENIC BACTERIA. 



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 i part of the diluted 

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

 concentrated aqueous fuchsin solution is added. It is 

 not necessary to prepare this mordant fresh for each 

 staining, as it seems to improve with age. The use of 

 acid and alkaline solutions added to the mordant is dis- 

 pensed with. 



The bacteria are carefully fixed to the glass, stained 

 with the mordant for five minutes, warming a little to- 

 ward the end, washed, dried, and subsequently colored 

 with carbol-fuchsin warmed a little. 



Bacteria can best be measured by an eye-piece microm- 

 eter. As these instruments vary somewhat in con- 

 struction, the unit of measurement for each objective 

 magnification or the method of manipulating the adjusta- 

 ble instruments must be learned from dealers' catalogues. 



Photographing bacteria requires special apparatus and 

 methods, which are fully described in text-books upon 

 the subject. 



