Note that in Figure 1 the central canal is continuous with the fourth
ventricle.

Figure 7. Histological elements.--
g.c., multipolar ganglion cell.
n., nucleus of a medullated nerve.
a.c., its axis fibre.
s.S., (sheath of Schwann), medullary sheath interrupted at intervals by
n.R., the nodes of Ranvier.
n.m.f., a non-medullated fibre.

{Illustration: Diagram Sheet 8.}

Sheet 9.

-The Nerves of the Rabbit_.

Figure I. Rough sketch of dissection of the neck from the left ventral
aspect.-- The bands of muscle between hyoid, mandible, and
sternum, and the thymus gland carefully cleared.
lr., is the larynx, and b., the balla.
s.m.g., the right sub-maxillary gland (the left has been removed).

The nerves are numbered.

l.r.l.n., [r.r.l.n.] is the left recurrent laryngeal looping under that
solid connection between the pulmonary artery (p.a.) and ao., the aortic
arch, which was an open tube in the embryo, the ductus arteriosus.
hy., is the hyoid with its posterior cornua.
ph.n., is the phrenic nerve.
r.r.l.n., [l.r.l.n.] is the right recurrent looping under the sub-clavian.
s.c.g., is the super or cervical ganglion of the sympathetic (sym.);
s.l.n., is the left superior laryngeal, and g. the left depressor
branch of x.
z., is the ramus descendens noni of the twelfth nerve.

In early development the heart lay just beneath the pharynx in the
position of the larynx (compare Dog-fish and Frog); as the neck
elongated, the heart shifted back with its vessels, and so the long
loop of the recurrent laryngeal comes to be drawn out in this singular
way.

Figure II. Diagram of orbit to show V.1 orbit-nasal, V.2 the maxillary,
and V.3 the mandibular branch of V. In order to show these in
dissection, the malar must be cut away, and the eye and glands of
the orbit removed.
s.r., e.r. [p.r.], i.r., and a.r., cut ends of the superior, external (or
posterior), inferior, and anterior (or internal) recti muscles.
s.o., and i.o., the superior and inferior obliques.

Figure III. General diagram of the Rabbit's cranial nerves.

Figure IV. Rough sketch of dissection of the nerves and
blood-vessels dorsal to stomach.--

The stomach turned over to the animal's right, the Spigelian liver lobe
cleared from the oesophagus, the mesentery supporting spleen and
hiding solar plexus picked off, and the mesentery hiding sympathetic
cleared.

coe.art., coeliac artery, and s.m.a., superior mesenteric artery.
coe.g. coeliac, and s