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of the hyomandibular, on the internal surface of the 
parasphenoid. They emerge from the canal into the 
deeper parts of the orbits and are inserted into the eye- 
balls on the inferior and middle surfaces, just underneath 
the insertion of the inferior obliques, so that their 
extremities are hidden by those of the latter muscles. 
The internal recti (7. int.)—Not so strongly developed 
as either inferior or superior recti. ‘They originate near 
the place of origin of the superior recti on the partition in 
the eye-muscle canal referred to. They run forwards in 
the orbit close to the interorbital septum, and are inserted 
into the eye-balls on the anterior and internal surface 
underneath the extremities of the superior obliques. 
The external recti (7. evt.)—These are the most 
slender of all the eye muscles. They take origin on the 
internal surface of the parasphenoid far back in the eye- 
muscle canal, and leave the latter above and externally. 
They are inserted Into the external and posterior surfaces 
of the eye-ball. A large portion of the distal extremity of 
each is tendinous, and contains little contractile tissue. 
With regard to the Bulbus oculi itself, we have only 
space to mention the more striking features in its 
anatomy. 
Blood vessels.—The afferent vessels of the bulb are 
(1) the ophthalmic artery, the origin of which has been 
already described, and (2) a small vessel springing from 
the circulus cephalicus between the origins of the internal 
carotid arteries. The efferent vessel is the superior 
jugular vein which begins its course in the eye. These 
vessels lie in the eye-muscle canal. They emerge from 
the latter accompanied by the optic nerve of their side 
with which they are bound up by a common sheath of con- 
nective tissue. Arrived at the eye all three perforate the 
