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THE NERVOUS SYSTE3I. 299
carotid plexus. Through this plexus it commuuicates with the cervi-
cal ganglion. As it extends forMard to the posterior border of the
ganglion, it occasionally unites with the long or sensory root, forming a
common trunk.
Variations in the Boots.—The ophthalmic ganglion may receiye
accessory roots from the superior division of the motor ocnli, the
lachrymal, abducens, or spheno-palatine ganglion (Henle, Tiedemann).
'' According to Reichart, the ophthalmic ganglion does not receive its
sympathetic fibres by a single root, but by several fine filaments, the
majority of which accompany the third nerve.
" It appears from the mode of development and arrangement in many
of the lower vertebrates that the o})hthalmic ganglion is morphologically
associated more intimately with the third nerve, having, in fact, the sig-
nificance of a spinal ganglion of that nerve (M. Marshall, Schwalbe)."^
Its branches of distribution are to the iris and ciliary muscles. The
short ciliary nerves, ten to fifteen in number, arise in two sets, superior
and inferior.
The Sujx'rior Set arises from the anterior superior angle, and passes
forward, in a wave-like manner, between the optic nerve and the supe-
rior rectus muscle to the posterior ])art of the eyeball.
Tlie Inferior Set is more numerous than the superior, and arises
from the anterior inferior angle of the ganglion. It passes in a wave-
like manner below the optic nerve and above the inferior rectus nuiscle
to the posterior part of the eyeball. It is accompanied by the long cil-
iary nerves which are derived from the nasal branch of the ophthalmic
division of the fifth. One or more of its fibres join the short ciliary nerves.
Both the superior and the inferior sets pass forward through the
sclerotic coat of the eye in delicate grooves on its inner sijrface, next to
the choroid coat, and are distributed to the ciliary muscle, the iris, and
the cornea. A small filament penetrates the optic nerve to the arteria
centralis retinae (Tiedemann).
Spheno-palatine Ganglion.
The spheno-palatine ganglion (ganglion of Meckel) (Fig. 146) is the
largest of the cranial ganglia. It is situated in the ])terygo-maxillary
fossa in front of the anterior opening of the Vidian canal, close to the
spheno-palatine foramen. It is triangular in form, with its apex point-
ing backward in the direction of the Vidian canal, and is surrounded
bv adipose tissue. Its outer surface is convex, and averages about one-
fifth of an inch in diameter. It is reddish-gray in color, excepting at
its broadest part, where it is composed entirely of gray matter.
The branches or roots of communication of the spheno-palatine
ganglion are
L The Sensor)/ Roots, two in number, which arise from the superior
maxillary nerve as it passes through the pterygo-maxillary fossa. They
enter the ganglion separately, one at the anterior and the other at the
posterior corner of the upper surface. ISIany of the fibres of these
roots pass through the ganglion without becoming incorporated with
^ Quain's Anatomy.
THE NERVOUS SYSTE3I. 299
carotid plexus. Through this plexus it commuuicates with the cervi-
cal ganglion. As it extends forMard to the posterior border of the
ganglion, it occasionally unites with the long or sensory root, forming a
common trunk.
Variations in the Boots.—The ophthalmic ganglion may receiye
accessory roots from the superior division of the motor ocnli, the
lachrymal, abducens, or spheno-palatine ganglion (Henle, Tiedemann).
'' According to Reichart, the ophthalmic ganglion does not receive its
sympathetic fibres by a single root, but by several fine filaments, the
majority of which accompany the third nerve.
" It appears from the mode of development and arrangement in many
of the lower vertebrates that the o})hthalmic ganglion is morphologically
associated more intimately with the third nerve, having, in fact, the sig-
nificance of a spinal ganglion of that nerve (M. Marshall, Schwalbe)."^
Its branches of distribution are to the iris and ciliary muscles. The
short ciliary nerves, ten to fifteen in number, arise in two sets, superior
and inferior.
The Sujx'rior Set arises from the anterior superior angle, and passes
forward, in a wave-like manner, between the optic nerve and the supe-
rior rectus muscle to the posterior ])art of the eyeball.
Tlie Inferior Set is more numerous than the superior, and arises
from the anterior inferior angle of the ganglion. It passes in a wave-
like manner below the optic nerve and above the inferior rectus nuiscle
to the posterior part of the eyeball. It is accompanied by the long cil-
iary nerves which are derived from the nasal branch of the ophthalmic
division of the fifth. One or more of its fibres join the short ciliary nerves.
Both the superior and the inferior sets pass forward through the
sclerotic coat of the eye in delicate grooves on its inner sijrface, next to
the choroid coat, and are distributed to the ciliary muscle, the iris, and
the cornea. A small filament penetrates the optic nerve to the arteria
centralis retinae (Tiedemann).
Spheno-palatine Ganglion.
The spheno-palatine ganglion (ganglion of Meckel) (Fig. 146) is the
largest of the cranial ganglia. It is situated in the ])terygo-maxillary
fossa in front of the anterior opening of the Vidian canal, close to the
spheno-palatine foramen. It is triangular in form, with its apex point-
ing backward in the direction of the Vidian canal, and is surrounded
bv adipose tissue. Its outer surface is convex, and averages about one-
fifth of an inch in diameter. It is reddish-gray in color, excepting at
its broadest part, where it is composed entirely of gray matter.
The branches or roots of communication of the spheno-palatine
ganglion are
L The Sensor)/ Roots, two in number, which arise from the superior
maxillary nerve as it passes through the pterygo-maxillary fossa. They
enter the ganglion separately, one at the anterior and the other at the
posterior corner of the upper surface. ISIany of the fibres of these
roots pass through the ganglion without becoming incorporated with
^ Quain's Anatomy.
