ORDINARY STAIN ING-SOLUTIONS 175 



bacteria we are indebted to Loffler. By a special method 

 of staining, in which the use of mordants played the essen- 

 tial part, he has shown that these organisms possess very 

 delicate, hair-like appendages, by the lashing movements 

 of which they propel themselves through the fluid in which 

 they are growing. The method as given by Loffler is as 

 follows : 



It is essential that the bacteria be evenly and not too 

 numerously distributed upon the cover-slip. The slips must 

 therefore be perfectly clean. (See Loffler' s method of clean- 

 ing cover-slips.) Five or six of the carefully cleansed cover- 

 slips are to be placed in a line on a 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 preparations. These slips are then dried and 

 fixed in the ordinary way. They are next to be warmed in 

 the following solution: 



Tannic acid solution in water (20 acid, 80 water) . 10 c.c. 

 Cold saturated solution of ferrous 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 a 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. 



There are several points and slight modifications in con- 



