STAINING. 155 
How is the staining fluid used ? 
Any one of the staining fluids used for this work just described is 
placed in a small watch glass. The section is put into the dye and the 
watch glass, held in a pair of forceps, is held just above a flame until 
steam and bubbles begin to form. It is then removed a little way. 
The process is then repeated several successive times, the whole opera- 
tion taking four or five minutes. 
What may be said concerning the use of the alcohol ? 
It must be used very carefully or else it will take all the color out 
of the bacteria to be stained. The object of its use is to get all the 
water out of the section so that the xylol and balsam will make it clear 
and transparent. 
What staining solutions are often used in staining spores ? 
The Koch-Ehrlich solution of fuchsin and also Ziehl’s carbol-fuchsin 
solution are used to stain the spores directly, while the remaining por- 
tion of the bacterium is stained with the ordinary methylin-blue 
solution. 
What ae formula of the Koch-Ehrlich solution and how is it 
use 
To a saturated watery solution of aniline oil a filtered saturated alco- 
holic solution of fuchsin is added, almost to the point of saturation. 
In using this the cover-glass preparation is floated, specimen side down, 
on its surface in a watch glass. Heat is applied intermittently for 
four or five minutes, and the specimen is then washed or rinsed in 
water and decolorized in a mixture of acid hydrochloric 3 ce. and abso- 
lute alcohol 100 cc., and again rinsed with water. The above acid 
mixture removes the red color (given by the fuchsin) from the body 
of the organism stained, but leaves it in the spores themselves. If 
now the methylin-blue solution is applied the decolorized portions of 
the organisms take up this blue color, which gives a marked contrast 
to the red staining of the spores. 
Give fue formula of Ziehl’s carbol-fuchsin solution and the method 
of use. 
B *Fuchsin (in powder).......-.sscseseeeeeees «1 gram. 
Acid carbolic (crystals)......c.scsseserseeseetens 5 grams. 
AIGORGL.. oss secg casceveccacauaesesacecceeneesans’s 10 ce. 
Distilled water........cssecesscesessereteneeeeeees 100 ce 
* Griibler’s aniline dyes should always be used. 
