204 BACTERIOLOGY. 
when the bacteria are stained in the ordinary manner. 
Special stains have been devised for causing the color to 
penetrate through the resistant spore. Thus in Abbott’s 
method the cover-slip after having been prepared in the | 
usual way is covered with a dye and held over the Bun- | 
sen flame until the fluid steams. This is continued for 
one or two minutes. It is then washed and dipped ina 
decolorizing acid solution, such as a 2 per cent. alco- 
holic solution of nitric acid, until all visible color has 
disappeared, then it is washed off and dipped for ten sec- 
onds in a solution containing 10 parts saturated alco- 
holic solution of eosin and 90 of water. The bacilli 
will then be rose-colored and the spores blue. Some- 
times, however, the spores refuse to take the stain in 
this manner. We then can adopt Moeller’s method, 
which is designed still further to favor the penetration 
of the coloring-matter through the spore membrane. 
He macerates the spores in a solution of chromic acid 
before staining them. The prepared cover-slip is held 
for two minutes in chloroform, then washed off in water, 
then placed from one-half to three minutes in a 5 per 
cent. solution of chromic acid, again washed off in 
water, and now restained by adding to it carbolic 
fuchsin, which is steamed for several minutes. The 
staining fluid is then washed off and the preparation 
decolorized in a 3 per cent. solution of hydrochloric 
acid or a 5 per cent. solution of sulphuric acid. The 
preparation is finally stained for a minute in methylene- 
blue solution. The spores will be red and the body of 
the cells blue. The different spores vary greatly in 
the readiness with which they take up the dyes, and 
we have, therefore, to experiment with each variety 
as to the length of time they should be exposed to the 
