AETIOLOGY OF TUBERCULOSIS. 
59 
tions bad been treated twenty-four hours with this color solution, there appeared 
in the tuberculous mass very fine staff-shaped forms, which, as further investiga¬ 
tion proved, had the power of increasing and forming spores, and therefore be¬ 
long to the same group of organisms as the inflammation-of-the-spleen bacilli. 
In section preparations it was incomparably more difficult to recognize these 
bacilli among the thickly heaped grains and masses of detritus, and it was there¬ 
fore attempted, following the example of Weigert, who, succeeding in the coloring 
of the inflammation-of-the-spleen bacilli a different color from the surrounding 
tissues, to make the tuberculous bacilli more plainly visible, by similar differen¬ 
tiating color reaction. This end was reached by the use of a concentrated watery 
solution of vesuvian, with which the blue colored, covered glass preparations and 
section preparations were treated so long, till to the naked eye, it seemed colored 
brown. Under microscopic examination it was then seen that only the previously 
blue-colored cell grains and the products of their disorganization had taken the 
brown color, but that the tuberculous bacilli remained a beautiful blue color, and, 
in consequence of this were very plainly to be distinguished from their surround¬ 
ings, so that even in the masses of grains, thickly heaped together, they were 
easily recognized. In the use of methyline blue in the manner just described, the 
bacilli, however, do not take a very intense color, and it requires a certain amount 
of practice to be able to prove their existence everywhere in tuberculous objects. 
Another method which gives to the bacilli a very strong color, we owe to 
Ehrlich. I use the same now exclusively, and earnestly recommend it to all 
who are beginning their studies of tuberculous bacilli. Ehrlich’s method has 
since received many unimportant modifications, partly improvements. Among 
the latter I would reckon the proportions of solutions as settled by Weigert and 
the shortening of the color solution, a change recommended by Rindfleisch. If 
I describe the method in which I use Ehrlich’s treatment as exactly as possible, 
I am nevertheless not of the opinion that the modification which I have followed 
is the best, or that just as good results are not to be gained by other modifications 
of the treatment. But the coloring of the tuberculous bacilli appears still to offer 
difficulties to many investigators, and for this reason, it will certainly not seem 
superfluous to give as exact directions as possible for the method of coloring. 
In order to prepare the color solution, aniline water and saturated alcoholic 
solutions of methyl violet (to be distinguished from methyline blue) or fuchsine 
are necessary. The aniline water is prepared in the following manner: About 5 
ccm. of pure aniline, an oil-like liquid, at first colorless, afterwards becoming 
brown, is poured into 100 ccm. of distilled water and this mixture is shaken re¬ 
peatedly. From three to four per cent, of aniline dissolves in the water and the 
rest remains in the bottom of the dish in the form of thick drops. After a sat¬ 
urated solution of aniline in water has been formed in this way, which is the 
case after about half an hour, this aniline water is filtrated through a filter, which 
has been moistened in order to separate it from the rest of the undissolved ani¬ 
line. The filtrate must be clear as water and colorless, and no little drops of 
aniline must be suspended in it. If such have passed the filter, the liquid must 
be filtrated again. 
One obtains the second ingredience of the color solution, the saturated solu¬ 
tion of methyl violet, by taking not too small a quantity (20 grm.) of dry methyl 
