786 
orbital, ciliary and muscular; the third is given 
off when the artery has passed over to the nasal 
side of the orbit, and consists of the ethmoidal, 
palpebral, nasal, and frontal arteries. 
e lachrymal artery is one of the largest 
branches of the ophthalmic ; it arises from the 
ophthalmic either within the optic hole or imme- 
diately after that artery has entered the orbit. 
It sometimes arises from the middle meningeal 
artery, and enters the orbit through the sphe- 
noidal foramen. It passes forwards along the 
outer wall of the orbit between the periosteum 
and the external rectus muscle; it enters the 
lachrymal gland, sending numerous branches to 
it; it then emerges from the gland and supplies 
the conjunctiva and the upper eyelid. It gives 
a malar branch which passes through the malar 
bone and anastomoses in the substance of the 
temporal muscle with the anterior deep tem- 
poral artery. The lachrymal artery generally 
anastomoses with the middle meningeal by a 
branch sent in through the sphenoidal fissure. 
The central artery of the retina is a small 
branch which enters obliquely the optic nerve ; 
it passes forwards in the centre of the nerve, 
enters the globe of the eye, and expands out 
into a vascular membrane on the inner surface 
of the retina. One small branch passes through 
the vitreous humour and reaches the posterior 
surface of the capsule of the lens. 
The supra-orbital artery arises from the oph- 
thalmic while it is above the optic nerve ; it is 
one of the largest branches of the artery: it 
passes forwards close under the periosteum of 
the roof, and above the levator palpebre, in 
company with the frontal nerve. It escapes 
from the orbit at the supra-orbital notch, and 
sends branches on the forehead, some between 
the skin and muscles, and others between the 
occipito-frontalis and the periosteum. In the 
orbit it supplies the levator palpebra and supe- 
rior rectus muscles, and sends some branches 
to the upper lid. 
The ciliary arteries are very numerous, and 
are divided into three sets—anterior, middle, 
and posterior. The anterior ciliary arteries are 
irregular in number and origin; they usually 
come off from the muscular branches at the 
anterior part of the orbit; they perforate the 
sclerotic about one or two lines behind the 
cornea: some branches go to the iris and anas- 
tomose with the long ciliary arteries; others go 
to the choroid and anastomose with the short 
ciliary. The middle or long ciliary arteries are 
two in number; they accompany the nerves of 
the same name. They pierce the sclerotic at 
some distance from the optic nerve, and pass 
horizontally one on each side between the scle- 
rotic and the choroid. They pass through-the 
ciliary ligament and supply the iris. The pos- 
terior or short ciliary arteries are remarkably 
delicate and tortuous ; they are accompanied by 
the ciliary nerves from the lenticular ganglion. 
Their origin is somewhat irregular; most of 
them arise from the ophthalmic artery, but oc- 
casionally some from the supra-orbital or from 
some muscular branches. There are as many as 
fifteen or twenty of these arteries, which sur- 
round the optic nerve in a spiral and tortuous 
ORBIT. 
manner; they pierce the sclerotic about two 
lines anterior to the oe of optic nerve, 
and supply the choroid and ciliary processes. 
(For ibe inode of arrangement of these ciliary 
per in the choroid and iris see the article 
LYE.) uy 
The muscular branches are uncertain in num- — 
ber and origin; they usually consist of two — 
sets, a superior and an inferior. The superior — 
set often come from the frontal artery, and 
supply the levator palpebre, the superior 
oblique and the superior rectus muscles. The 
inferior muscular artery is a regular branch 
from the ophthalmic ; it descends on the inner 
side of the optic nerve ; it first sends a t 
to the external rectus and then suppli 
inferior and internal recti, and n 
oblique; some branches pass on to the 
eyelid and the lachrymal sac. These arterie 
are usually distributed to the ocular surface o 
the muscles. 7. 
The ethmoidal arteries, two in number, 
given off from the ophthalmic near the inne’ 
— of the orbit. The posterior is usually 
arger; it passes through the ae 
foramen dick nests the skull, where it sends 0 
some anterior meningeal branches, then passe 
down through the cribriform plate of the ¢ 
moid bone, and is distributed on the muce 
membrane of the nose. The anterior ethmoid: 
passes through the anterior internal orbital f 
men with the nasal nerve; it has the sai 
distribution as the posterior braiich. . 
The palpebral arteries, two in number, 
near the inner angle of the orbit. The superi 
arises above the tendon of the orbicularis palp 
brarum ; it passes outwards and supplies 
upper lid, one branch running near tt 
margin of the lid, while the others are di 
buted to the muscles and integuments of | 
middle and upper part of the lid, where 
anastomose with the sap ae a 
inferior palpebral artery own beh 
the reckon nf the obicaarial then runs 0 
wards along the lower lid, forming an 4@ 
near the free margin of the lid, and is grada@ 
lost near the external canthus. It anastom 
with the angular branch of the facial, wit 
infra-orbital branch of the internal maxil 
with the transverse facial and temporal art 
Beneath the internal angular process the 
thalmic artery terminates by dividing inte 
nasal and the frontal branches. . 
The nasal artery emerges from . 
above the tendon of the orbicularis; it at 
moses freely with the angular artery, 
branches to the lachrymal sac, and tert 
in a branch which passes down the de 
the nose, and communicates at the € 
of the nose with the corresponding ai 
the opposite side. mi 
The frontal artery passes out of th 
with the nasal, then turns upwards, and 
tributed to the muscles and integument 
forehead, anastomosing with the supra: 
and with the arteries of the opposite side 
The ophthalmic vein commences at the 
angle of the orbit, where it communic 
with the angular and frontal veins; it 
Dab > 
-e 2 
Oro 
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