194 THE AMERICAN MONTHLY [October, 
or all of the tubercle bacilli are decolorized. They should remain in the acid 
until the red (fuchsin) or blue (methyl violet) hue has changed into a yellowish 
red or greenish blue. At this stage the preparations are placed in water, and 
again a red or blue color appears. By the action of the acid the simple acid ° 
union (red or blue) is changed to a triple acid (yellow-red or blue-green), and, 
by the addition of the water, the triple acid union is destroyed’and the red or 
blue hue reappears. The preparations decolorized by the acid are not washed 
in water, but in 50 or 60 per cent. alcohol ; then they are stained in a dilute 
solution of methyl blue (or vesuvin). After washing away the methyl] blue 
(or vesuvin) the preparations are examined in water, or, after removal of the 
water, preserved in Canada balsam. 
After this whole procedure the tubercle bacilli retain their red or blue color, 
and are easily recognized among the other elements. Aside from this differ- 
ential diagnostic action of the double-staining, the subsequent staining in 
another color has an advantage by affording an easier examination of the 
specimens. 
Concerning the choice of material containing bacteria, it is to be noted that 
the cheesy masses are to be spread out thin with a sterilized scalpel. Nodules 
of tubercle must be crushed with a scalpel, or between two scalpels, and then 
be pressed flat upon the cover-glass. The tough yellowish masses from the 
sputum are used. One of these particles is taken and spread out in a thin 
layer on the cover-glass, or flattened by pressing one cover-glass upon another, 
so that, after separating the two cover-glasses with pincettes, two preparations 
are obtained. The entire method is, according to Koch (after the adoption 
of the anilin-water staining of Ehrlich), briefly, as follows :— 
1. Pass the dried cover-glass preparations three times through the flame. 
2. Stain with Weigert-Koch* solution of methyl violet or fuchsin for twelve 
hours. 
3. Treat with dilute nitric acid (1 to 3 or 4) for a few seconds. 
4. Wash in a 60-per cent. solution of alcohol by a to-and-fro motion. 
5. Stain in a dilute solution of a vesuvin or methyl! blue. 
6. Wash and examine in water or mount in balsam. 
This method is the best thus far discovered, and serves as a control in all 
doubtful cases. 
MICROSCOPICAL TECHNIQUE 
Notes on staining vegetable tissues. 
By W. R. LIGHTON, 
LEAVENWORTH, KANSAS. 
Those who are at the beginning of the study of microscopic science are 
not unfamiliar with the beauties of stained and double-stained organic tissues, 
and yet there are probably few who have watched this staining process while 
going on in the tissues of living plants. The following is a simple way in 
which one can follow the process and get a clear insight into the principles 
of circulation. 
If a fresh green stem is cut from a plant and the newly-cut end be placed 
in a solution of any of the substances commonly used for staining, this color- 
ing matter will gradually be absorbed in the process of circulation and be 
distributed through the tissues. Select a plant with the leaves sufficiently 
+ Saturatedianilinnwa tere) \. slain it tenet atonement Ml, ie mn gener OOLGSCr 
Concentrated alcoholic solution, methyl violet orfuchsin . . 11C.c. 
Absolutetalcoholl cg. <yyuetire ep atamiae de cee RENAN Koa: s MR ORC ae 
This solution cannot be kept more than ten or twelve days without losing its coloring power. 
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