186 BACTERIOLOGY. 



in different stages of development. Some stain readily 

 by either of the methods especially devised for this 

 purpose, while others can hardly be stained at all, or 

 only with the greatest difficulty, by any of the known 

 processes ; some stain readily when fully developed, but 

 with difficulty when only partly developed ; others have 

 this peculiarity reversed. 



LOFFLER'S METHOD FOR STAINING FLAGELLA. 

 For the demonstration of the locomotive apparatus pos- 

 sessed by motile bacteria we are indebted to Loffler. 

 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 Loffte^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 : 



Tannicacid 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. 



