The Character of the Flagella 349 



Fuchsin i gram 



Absolute alcohol 10 cc. 



A 5 per cent, solution of carbolic acid 100 cc. 



The fuchsin is dissolved in the alcohol, after which the acid 

 solution is added. 



The cover-glass preparations: The cover-glasses must be 

 perfectl}^ clean. The desired number of cover-glasses are 

 then arranged on a level tray. A large drop of 7var77i water 

 (distilled or hydrant) is placed upon each cover-glass by 

 means of a sterile pipette. If the cover-glass is properly 

 cleaned * the drop of water will spread over its entire surface. 

 The point of a cooled, flamed platinum wire is very gently 

 touched to the surface growth of the germ on agar or gelatine 

 and carefully immersed in the water near the center of the 

 cover-glass. A sufficient number of bacteria will adhere to 

 the wire to make from six to ten preparations. The tray with 

 the cover-glasses is then placed in an incubator at a tempera- 

 ture of about 36° C. until the water is evaporated. Many of 

 the bacteria on account of their power of locomotion, and by 

 means of the currents produced in the liquid during its evap- 

 oration, will be found, in the dried preparations, to be isolated 

 from the clumps of bacteria that were introduced with the 

 wire and distributed very evenly over a large portion of the 

 surface of the cover-glass. This natural distribution prevents, 

 to a marked extent, the breaking off of the flagella which 

 occurs when the distribution is made by mechanical means 

 in a smaller quantity of the diluent. If the water to be used 



* Weber {Fortschritte der Medicin Bd. XI. (1893), p. 49) has found 

 that when the percentage of calcium is too small in proportion to the 

 alkalies (sodium and potassium) in the composition of the glass, the 

 atmosphere will produce a chemical change in the glass which gives its 

 surface a peculiar moist condition. This may explain to some extent 

 the cause of the deeply stained background where the proper precau- 

 tions were taken to prepare the cover-glasses. I have frequently no- 

 ticed that in the use of cover-glasses that had been cleaned and ex- 

 posed to the atmosphere for a considerable time prior to their use, the 

 water would " roll up" in drops, as though the surface was covered with 

 a film of oil, and when stained they would invariably exhibit a deeply 

 stained background. 



