140 BACTERIOLOer. 



themselves through the fluid in which they are located. 

 The method as given by Loffler is as follows : 



(1) It is essential that the bacteria be evenly and 

 not too numerously distributed upon the cover-slip. The 

 slips must therefore be carefully cleansed. (See Lqffler's 

 method of cleaning cover-slips.) Five or six of the 

 carefully cleansed cover-slips are to be placed in a line 

 on the table, and on the centre of each slip a very small 

 drop of tap-water is placed. From the culture to be 

 examined a minute portion is transferred to the first 

 slip and carefully mixed with the drop of water ; from 

 this mixture a small portion is transferred to the 

 second, and from the second to the third slip, and so 

 on — in this way insuring a dilution of the number of 

 organisms present in the preparation. 



These slips are then dried and fixed in the ordinary 

 way. They are next to be warmed in the following 

 solution : 



Tannic acid solation in water (20 acid, 80 water) . 10 o.e. 

 Cold saturated solution of ferro-sulphate . . 5 c.c. 



Saturated watery or alcoholic solution of fuchsin . 1 c.c. 



This solution represents the mordant. A few drops 

 of it are to be placed upon the film of bacteria on the 

 cover-slip, which is then to be held over the flame until 

 the solution begins to steam. It should not be boiled. 

 After steaming, the mordant is washed off in water and 

 finally in alcohol. The bacteria are then to be stained 

 in a saturated aniline-water fuchsin solution. 



When treated in this way different bacteria behave 

 differently : the flagella of some stain readily in the 

 above solutions ; others require the addition of an alkali 

 in varying quantities ; while others stain best after the 

 addition of acids. To meet these conditions an exact 



