60 
R. KOCH. 
violet in a well closing glass vessel, pouring over it 100-150 ccm. of absolute 
alcohol and shaking it repeatedly. After standing a day, there must still be un¬ 
dissolved methyl violet at the bottom of the vessel, which of course can also be 
dissolved and made use of by gradually pouring on more alcohol. When in place 
of methyl violet, fuchsine is used, which seems to offer certain advantages for 
permanent preparations, one also proceeds in the just described manner. 
After this, the alcoholic methyl violet solution and the aniline water are to 
be mixed, and according to Weigert in the proportion of 100 ccm. aniline water 
to 11 ccm. methyl violet solution. I add to this mixture 10 ccm. of absolute al¬ 
cohol, because I have found that then the color solution remains usable in a well 
closed glass for about ten days and does not need to be filtered each time before 
using. 
The preparations which are to be examined with reference to tuberculous 
bacilli are to be prepared in the following manner: Covering glasses are to be 
freed from fat and all other extraneous matter, which might prevent adhesion of 
the substance to be examined, by washing in nitric acid and cleaning with alco¬ 
hol. The substance is then to be spread out on the covering glass in as thin a 
section as possible. This procedure succeeds best when soft caseous masses are 
treated ; they can be spread out evenly and thin with a scalpel or a needle. Fir¬ 
mer, crumby caseous masses must be carefully crushed with the scalpel and ar¬ 
ranged on the glass by spreading out repeatedly. Still more difficult is it to 
prepare a little tuberculous knot, which possesses a compact consistence. It 
must be completely crushed and pressed to pieces on the covering glass. The 
preparation of covering glasses with sputum also demands a special technique. 
One must not content himself with taking any chance list of mucus from the 
sputum, since the sputum consists not only of the secretion of the diseased parts 
of the lungs, but also of bronchial secretion and mucus from the mouth and nose. 
It is on this account necessary to examine only those parts of the sputum which 
have separated themselves from the diseased lungs, that is to say, the yellowish 
lumps which often swim solitarily in the frothy slimy liquid, which to be sure 
often forms the greatest part of the sputum. Such a lump of this yellowish, ex¬ 
tremely tough mass should be drawn to the edge of the glass, then a little bit of 
it separated with the scalpel, drawn out of the liquid and on to the inner wall of 
the glass. Here it can easily be further divided, and be taken off in as large par¬ 
ticles as one wishes to transfer to the covering glass. On this it is spread out 
very evenly and thinly, and any residue should be brought to a corner of the cov¬ 
ering glass, and from there removed with blotting paper. 
After the covering glass has been prepared in this manner, the section spread 
out upon it must be allowed to become thoroughly dry. Not until this is the case 
can the covering glass be heated temporarily, in order to make the section insolu¬ 
ble in watery fluids, with which it is now brought in contact. The covering glass 
can be put into a drying box heated to 110° for twenty minutes, or one can hold 
the covering glass with a pincette, and draw it several times, not too quickly, 
through a gas or spirit flame. The prepared section of the covering glass is dur¬ 
ing this process to be on the upper side and is not directly touched by the flame. 
That the forms of the bacteria cells, etc., which occur in the section are not 
changed in the least by this careful process, can be shown by the following ex- 
