770 THE VASCULAR SYSTEM. 
(2) The Vidian is a small and inconstant branch which accompanies the great 
deep petrosal nerve in the Vidian canal; it anastomoses with the Vidian branch of the 
internal maxillary artery. 
In the cranitum.—(1) Cavernous, small branches to the walls of the cavernous sinus 
and to the third, fourth, fifth, and sixth nerves. 
(2) Gasserian, minute twigs which supply the Gasserian ganglion. 
(3) Pituitary branches pass to the pituitary body. 
(4) Meningeal branches ramify in the dura mater of the middle cranial fossa, anasto- 
mosing with the branches of the middle and small meningeal arteries. 
(5) Ophthalmic Artery (a. ophthalmica, Fig. 556).— This artery springs 
from the front and inner side of the internal carotid as it turns upwards on the 
inner side of the anterior clinoid process. It passes forwards and outwards, beneath 
the optic nerve and through the optic foramen into the orbital cavity. In the 
orbit it runs forwards for a short distance on the outer side of the optic nerve, and 
it is in relation externally with the lenticular ganglion and the external rectus 
muscle; turning upwards and inwards, it crosses between the optic nerve and 
Middle internal frontal artery Corpus callosum Septum Ineidum 
Posterior internal frontal artery 
Parieto-occipital 
artery 
Anterior 
internal 
frontal — [{ X 
artery y oN 
Internal orbital 
artery 
Anterior cerebral. —_ 
artery 
External orbital artery~ 
Middle cerebral artery Calearine artery 
Temporal branch of middle cerebral Posterior cere- Crus Temporal branches of posterior cerebral 
bral artery cerebri 
Fig. 557.—DIsTRIBUTION OF THE CEREBRAL ARTERIES ON THE MESIAL, TENTORIAL, AND INFERIOR 
SURFACES OF THE CEREBRAL Hi&rMISPHERES. 
The anterior cerebral artery is coloured green, the middle cerebral artery red, and the 
posterior cerebral artery orange. 
the superior rectus to the inner wall of the orbit, where it turns forwards to 
terminate at the inner and front part of the orbital cavity by dividing into frontal 
and nasal branches. It is accompanied at first by the nasal nerve, and in the 
terminal part of its course by the infra-trochlear nerve. 
Branches.—The branches of the ophthalmic artery are numerous. (#) The posterior ciliary, 
usually six to eight in number, run forwards at the sides of the optic nerve ; they soon divide 
into numerous branches which pierce the back part of the sclerotic coat ; the majority terminate 
in the choroid coat of the eye as the short ciliary arteries (aa. ciliares posteriores breves), but two 
of larger size, the long ciliary arteries (aa. ciliares posteriores long), run forwards, one on each 
side, almost in the horizontal plane of the eyeball, between the sclerotic and the choroid coats, to 
the base of the iris, where they divide. The resulting branches anastomose together and form a 
circle at the outer periphery of the iris, from which secondary branches run inwards and anasto- 
mose together in a second circle near the inner margin of the iris. 
(6) The central artery of the retina (a. centralis retinc)-arises near to, or in common with, the 
preceding vessels. It pierces the inner and under side of the optic nerve about half-an-inch (12 
mm.) behind the sclera, and runs in its centre to the retina, where it breaks up into terminal 
branches. 
(¢) Recurrent (a. meningea anterior)—A small branch which passes backwards through the 
sphenoidal fissure into the middle fossa of the cranium, where it anastomoses with the middle and 
small meningeal arteries, and with the meningeal branches of the internal carotid and lachrymal 
arteries. > 
