168 BACTERIOLOGY. 



MOELLER'S METHOD FOR STAINING SPORES. A 

 method that has recently been published by Moeller 

 is designed to favor the penetration of the coloring- 

 material 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 held 

 for two minutes in chloroform, washed in water, placed 

 for from one-half to two minutes in a 5 per cent, solu- 

 tion of chromic acid, again washed in water, and stained 

 with carbol-fuchsin. In the process of staining, the slip 

 is taken by the corner with forceps, and carbol-fuchsin 

 is dropped upon the side containing the spores. It is 

 then held over a flame until it boils, and then held 

 some distance above the flame for one minute. The 

 staining-fluid is then poured off and the preparation is 

 completely decolorized in 5 per cent, sulphuric acid, 

 again washed in water, and finally stained for thirty 

 seconds in the watery methylene-blue solution. The 

 spores will be red, the body of the cells blue. 



In this method the object of the preliminary ex- 

 posure to chloroform is to dissolve any crystals of leci- 

 thin, cholesterin, or fat that may be in the preparation, 

 and which when stained might cause confusion. 



It must be remembered that there are conspicuous 

 differences in the behavior of spores of different bacteria 

 to staining-methods and of the spores of a single species 

 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 



