ing strength up to absolute, keeping in
each strength for twenty-four hours.

9. Clear, embed, cut very thin sections, mount, remove paraffin, again
clear and mount in xylol balsam.

The spirochaetes if present are black and show up against the pale yellow
color of the background.

Weak carbol fuchsin, neutral red or toluidin blue can also be used to
stain the background if desired, after the removal of the paraffin in
step 9.

~To Demonstrate Protozoa in Sections (Leishman).~--

Reagents required:

Leishman's Polychrome stain.
Acetic acid 1 in 1500 aqueous solution.
Caustic soda 1 in 7000 aqueous solution.
Distilled water.

1. Mount section, remove paraffin and take into distilled water as usual
(_vide_ page 121).

2. Drain off the excess of water.

3. Cover the section with diluted Leishman (1 part stain, 2 parts
distilled water) and allow to act for five to ten minutes (until tissue
appears a deep blue).

4. Decolourise with acetic acid solution until only the nuclei appear
blue (examine the section wet, with low power objective).

5. If the eosin colour is too well marked treat with the caustic soda
solution until the desired tint is obtained (as seen with the 1/6-inch
objective).

6. Wash with distilled water.

7. Rapidly dehydrate with alcohol.

8. Clear with xylol.

9. Mount in xylol balsam.

~VIII. CLASSIFICATION OF FUNGI.~

For practical purposes FUNGI may be divided into:

~1. Hymenomycetes~ (including the mushrooms, etc.).
~2. Hyphomycetes~ (moulds).
~3. Blastomycetes~ (yeasts and torulae).
~4. Schizomycetes~ (bacteria).

NOTE.--Formerly myxomycetes were included in the fungi; they
are now recognized as belonging to the animal kingdom, and
are termed "mycetozoa."

~MORPHOLOGY OF THE HYPHOMYCETES.~

At the commencement of his studies, the attention of the student is
directed to the various non-pathogenic moulds and yeasts, not only that
he may gain the necessary technique whilst handling cultivations of
harmless organisms, but also because these very species are amongst the
commonest of those that may accidentally contaminate his future
preparations.

The hyphomycetes are composed of a mycelium of short jointed rods or
"hyphae" springing from an axis or germinal tube which develops from the
spore. Hyphae are--

(a) Nutritive or submerged.

(b) Reproductive or aerial.

The protoplasm of these cells contains granules,