a) _Subdural._

1. Anaesthetise the animal and secure it to the operating table, dorsum
uppermost.

2. Shave a portion of the scalp immediately in front of the ears.

[Illustration: FIG. 187.--Guy's electrical dental engine.]

3. Mark out with a sharp scalpel a crescentic flap of skin muscle, etc.,
convexity forward, commencing 0.5 cm. in front of the root of one ear
and terminating at a similar spot in front of the other ear. Reflect the
marked flap.

4. Make a corresponding incision through the periosteum and raise it
with a blunt dissector.

5. With a small trephine (diameter 6 mm.) remove a circular piece of
bone from the parietal segment. The centre of the trephine hole should
be at the intersection of the median line and a line joining the
posterior canthi (Fig. 188).

6. Introduce the inoculum by means of a hypodermic syringe, perforating
the dura mater with the needle and depositing the material immediately
below this membrane, at the same time taking care to avoid injuring the
sinuses.

7. Turn back the flap of skin and secure it in position with Michel's
steel clips.

8. Dress with sterile gauze and wool and seal the dressing with
collodion.

9. Label, etc.

(b) _Intracerebral._--This inoculation is performed precisely as for
subdural save in step 6 the needle after perforating the dura mater is
pushed onward into the substance of one or other cerebral hemispheres
before the contents are ejected.

[Illustration: FIG. 188.--Intracranial inoculation of rabbit. The circle
indicates the situation of the trephine hole.]

~6. Intraocular.~--

(a) _Fluid Inoculum._--(_Anaesthetic, cocaine._)

1. Instil a few drops of a sterile solution of cocaine, and repeat the
instillation in two minutes.

2. Five minutes later have the animal firmly held by an assistant as in
intravenous injection (see Fig. 189), the head being steadied by the
assistant's hands.

3. Select two needles to accurately fit the same syringe and sterilise.

4. Attach one needle to the syringe and take up the required dose of
inoculum and remove the needle.

5. Steady the eye with fixation forceps; then pierce the cornea with the
other syringe needle and allow the aqueous to escape through the needle.

6. Without removing the needle from the cornea attach the syringe and
make the injection into the anterior chamber.

7. Irrigate the conjunctival sac with sterile saline solution.

8. Label, etc.

(b) _Solid Inoculum._--(_An