late of freezing microtome and freeze
with carbon dioxide vapour.

4. Float the sections off the knife into a glass dish of
tepid water.

5. Stain the sections in glass capsules containing selected
stains.

6. Place the stained section in a dish of clean water and
introduce a glass slide obliquely beneath the section; with
a mounted needle draw the section on to the slide and hold
it there; gently remove the slide from the water, taking
care that any folds in the section are floated out before
the slide is finally removed from the water.

7. Drain away as much water as possible from the section.
Drop absolute alcohol on to the section from a drop bottle,
to dehydrate it.

8. Double a piece of blotting paper and gently press it on
the section to dry it.

9. Drop on xylol to clear the section.

10. Place a large drop of xylol balsam on the section and
carefully lower a cover-glass on to the balsam.

PARAFFIN METHOD.

1. ~Fixation.~ Place the pieces of tissue, resting on cotton-wool, in a
wide-mouthed glass bottle. Pour on a sufficient quantity of the
corrosive sublimate fixing fluid; allow the tissue to remain therein for
twelve to twenty-four hours according to size.

2. Pour off the fixing fluid and wash thoroughly in running water for
twenty minutes to half an hour to remove the excess of corrosive
sublimate.

[Illustration: FIG. 72.--~L~-shaped brass moulds.]

[Illustration: FIG. 73.--Paraffin kettle.]

3. ~Hardening.~ Place the tissues in each of the following strengths of
alcohol in turn for from twelve to twenty-four hours: 50 per cent., 75
per cent., 90 per cent., absolute.

4. ~Dehydration~ is effected by transferring the tissues to fresh absolute
alcohol.

5. ~Clearing.~ Half fill a wide-mouthed bottle with chloroform. On the
surface of the chloroform float a layer of absolute alcohol about five
to ten millimetres in depth. Place the pieces of tissue in the layer of
alcohol and when they have sunk through this layer, transfer them to
pure chloroform for from six to twenty-four hours according to the size
of the pieces. When "cleared," the tissue becomes more or less
transparent.

6. ~Infiltration.~ Place the cleared tissues in fresh chloroform with
several pieces of paraffin wax and stand in a warm place, such as on the
top of the warm incubator. The warmth gradually melts the paraffin and
the