138 BACTERIOLOGY. 



then held by its edge with the forceps about 2 cm. above 

 a very small flame of a Bunsen burner, care being taken 

 that the flame touches only the centre of the bottom of 

 the crystal. After a few seconds the crystal is elevated 

 gradually until it is about 6 to 8 cm. above the flame, 

 then it is slowly moved down to the flame again, and 

 this up-and-down movement is continued until the 

 staining fluid begins to boil. As soon as a few bubbles 

 have been given off it is held aside for a minute or two 

 and the process of heating is repeated. When the 

 boiling begins, the crystal is held aside again for a 

 minute or two. The crystal is heated in this way for 

 about five or six consecutive times. When the fluid 

 has stood for about five minutes after the last boiling, 

 the preparation is transferred, without washing in 

 water, into a second watch-crystal containing the fol- 

 lowing decolorizing solution : 



Absolute alcohol . . .... 100 c.c. 



Hydrochloric acid 3 c.c. 



In this solution it is placed, bacteria up, and the 

 vessel is tilted from side to side for about one minute. 

 It is then removed, washed in water, and stained with 

 the methylene-blue solution. The spores will be stained 

 red and the body of the cells will be blue. 



Moellee's Method for Staining Spores. — A 

 method that has recently been published by Moeller is 

 designed to favor the penetration of the coloring mate- 

 rial through the spore membrane by macerating the 

 spores in a solution of chromic acid before staining 

 them. It is as follows : 



The cover-slips are prepared in the usual way, or the 

 fixing may be accomplished with absolute alcohol in- 

 stead of high temperatures. The preparation is then 



