72 BACTERIOLOGY 



warming the staining fluids. Carbolic acid fuchsine (ZiehVs 

 solution) is used for staining, and the infected cover-glass is 

 left for an hour in the boiling dye, when the spores in the 

 bacilli will remain of a red colour after washing with water 

 and decolorising with alcohol ; or if double staining with 

 methyl blue is carried out the bacilli appear blue, and the 

 spores dark red. The hay bacillus, and especially the Bacillus 

 megatherium, should be selected for the study of these methods 

 of staining. In many of the microbes hitherto known the 

 discovery of spores has not as yet been made. 



Spores are also brought out distinctly as little granules 

 by staining with dilute alkaline methyl blue, in which case, 

 after double staining with aqueous solution of Bismarck 

 brown, they appear blue on a brown ground. 



According to Moeller, spores are most conveniently 

 stained by the following method : The cover-glass prepara- 

 tion is brought for two minutes into absolute alcohol aiid for 

 two more into chloroform, washed in water, plunged for from 

 a half to two minutes into a 5 per cent, chromic acid solu- 

 tion and rinsed again with water, after which some aqueous 

 carbolic fuchsine solution is dropped on, and it is warmed 

 for one minute in the flame, being brought once to the 

 boil. The carbolic fuchsine is poured off, the cover-glass 

 dipped into 5 per cent, sulphuric acid until decolorised, and 

 once more thoroughly washed with water. Finally, an 

 aqueous solution of methyl blue or malachite green is 

 allowed to act on it for half a minute, and then washed off. 

 The spores are dark red in the interior of blue or , green 

 bacteria. 



DECOLORISING AGENTS 



In staining with the various aniline dyes a phenomenon 

 of practical importance has been observed, viz. that stained 

 micro-organisms part with their colouring matter to certain 



