52 TEXT-BOOK OF BACTERIOLOGY. 



ing, a membrane with great powers of resistance against exterior 

 influences. 



This membrane obstinately refuses to admit our ordinary stain- 

 ing matters into the interior of the spore. 



If we treat a preparation containing spores with a solution of 

 gentian-violet ever so long, they (the spores) remain as uncolored, 

 brightly-shining gaps, of the well-known egg-like shape, which con- 

 trast with the fully-colored residuum of the bacterium not employed 

 in forming the spore. 



It is therefore necessary to resort to the most active means in 

 order to overcome the resistance offered by the spore-membrane to 

 the penetration of coloring matter. When this is done, the stain 

 is, as it were, surrounded by a protecting mantle, its retreat is cut 

 off, and it can now only with great difficulty be removed again. 



After this explanation, the process of spore-staining will at once 

 be understood. We stain the cover-glass, with spore-bearing bac- 

 teria for an hour in Ziehl's solution, hot, or still better, boiling. 



This is done by keeping a small dish of carbol-fuchsin at the 

 boiling point by means of a gas-flame or spirit-lamp, and from 

 time to time adding of the solution sufficient to make up for the 

 loss by evaporation. 



Then the spore is penetrated by the red coloring matter, which 

 is now just as hard to remove as it was to retain in the first place. 

 From the remaining part of the cell, however, it can easily be re- 

 moved. If the cover-glass be now treated with diluted or pure 

 alcohol, the spore retains its color and the rest of the cell is decol- 

 orized. 



The spores are clearly visible as bright red, egg-shaped forma- 

 tions, while scarcely anything remains visible of the other part of 

 the cell. But that it really is there, and only requires a little aid 

 to again become distinctly visible, will be seen if we employ a con- 

 trasting color (for red, the best is blue), and of course it must be a 

 bacterial stain. A diluted alcoholic solution of methyl-blue is greed- 

 ily absorbed by the cell, and in such a double-stained preparation 

 one sees the deep red spores' lying in rows in their deep blue cells 

 like a string of beads. The picture is really beautiful and well cal- 

 culated to show the advantages of staining-. 



All the spores of the different kinds of bacteria do not by any 

 means behave in the same manner under the treatment above de- 

 scribed. As regards their powers of resistance to other influences, 

 Buch as heat, chemicals, etc., a difference of behavior has been ob- 

 served, and it is therefore not surprising that some spores yield but 

 Slowly, others very quickly, to the specific stains. The anthrax 



