LOFFLER'S METHOD FOR STAINING FLAGELLA. 1 69 



processes ; some stain readily when fully developed, but 

 with difficulty when only partly developed ; others have 

 this peculiarity reversed. 



LOFFLER'S METHOD FOB STAINING FLAGELLA. 

 For the demonstration of the locomotive apparatus pos- 

 sessed by motile bacteria we are indebted to Loftier. 

 By a special method of staining, in which the use of 

 mordants played the essential part, he has shown that 

 these organisms possess very delicate, hair-like appen- 

 dages, 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 cleaning 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 fuchsiu ... 1 c.c. 



This solution represents the mordant. A few drops 

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



