72 
Laboratory Note. 
Place a few c.cs. in a corked tube. Into this stain drop masses 
of the fresh, living filaments, drained as far as possible of their 
superfluous water. Leave them in for three days—a somewhat 
longer immersion does no harm—and then remove and wash in 
distilled water. Soak for two to three minutes in either 5 % 
Sulphuric acid or 5% Potash Solution, to dissolve the “meta- 
chromatic granules,” which also take the stain, and re-wash in 
distilled water. Mount in a drop of the highly refractive medium 
made by dissolving in a saturated solution of Pot. Iodide, as much 
Mercuric Iodide as it will take up. This medium has a Refractive 
Index approximating to that of flint glass, and is useful for many 
purposes, as no dehydration is necessary, while the full aperture of 
immersion lenses may be brought to bear upon objects mounted in it. 
This gives very fine, although ephemeral results. The “ central 
body” stains dark blue, the peripheral protoplasm yellow. The 
preparations will not last more than twenty-four hours, but this is 
long enough for demonstration or drawing purposes. 
If permanency is an object the preparation must be brought 
rapidly up from water to 70% alcohol and then dehydrated by means 
of aniline, cleared in cedar (not clove) oil and mounted in xylol- 
balsam or dammar. The results however are not as brilliant as by 
the first method. 
