THE STAINING OP FLAGELLA. 317 



In order to obtain good stains of flagella special care 

 must be given to the preparation of tlie cover-glasses. 

 These should be cleaned according to the method given on 

 p. 140, and when spread must contain as little organic mat- 

 ter as possible in order to prevent the formation of a dirty 

 precipitate on the cover-glass. Excellent cover-glasses 

 can be made by resorting to dilution. For this purpose, a 

 small loopful of the turbid fluid found on top of the agar 

 stab culture, or at the bottom of the inclined agar culture 

 of the edema bacillus No. II, or of the symptomatic an- 

 thrax bacillus, is transferred to a large drop of distilled 

 water on a glass slide. 



By means of a straight platinum wire, three transfers 

 are made from this drop to another drop of distilled water 

 on the same slide. This second drop will now contain only 

 a small number of bacteria and very little foreign matter. 

 By means of a platinum wire, with a very small loop, not 

 much larger than a pin-head, transfers can now be made to 

 six or eight clean wide cover-glasses. Each small loopful 

 is spread at once over as much of the surface of the cover- 

 glass as possible. The thin film of liquid evaporates al- 

 most immediately, and the cover-glass can then be fixed by 

 passing it once through the flame. Over-heating the cover- 

 glass is very likely to destroy the slender flagella. This 

 can be prevented if the cover-glass is held between the 

 thumb and index finger as it is passed through the flame. 



The cover-glass, with the specimen side up, is held in 

 a pair of forceps and covered, by the aid of a pipette, with 

 the hot mordant solution. The cover-glass is then held 

 over the flame for about a minute. The flame should be 

 turned down till it is less than 1^-2 inches high. The 

 liquid should be warmed so as to give off vapors, but 

 should not be actually boiled. As fast as evaporation 

 takes place fresh mordant solution should be added, and 

 at no time should it be allowed to dry down on the cover- 

 glass. 



