166 ANTHROPOLOGY. 



The obliquus superior or trochleator arises from the sheath of the optic 

 nerve, and from the inner margin of the optic foramen. It passes forwards 

 and ends in a round tendon, which passes through the cartilaginous pulley 

 attached by a movable fibrous ligament to a depression behind the inner 

 angle of the os frontis ; the tendon then passes backwards and outwards, 

 and is inserted into the posterior part of the sclerotic coat between the 

 superior and external recti. In some instances the pulley is bony instead 

 of cartilaginous. 



The inferior oblique muscle is the shortest of the group, and the only -one 

 that is not connected to the apex of the cavity, being situated at the 

 inferior and anterior part of the orbit, behind the lower eye-lid. It arises 

 from a rough ridge within the orbital margin of the superior maxillary bone 

 external to the lachrymal sac, and ends in a broad thin tendon which 

 ascends between the eye and the external rectus, becoming inserted into 

 the posterior external part of the sclerotic. The two oblique muscles are 

 adapted to rotate the eye on its axis. The recti muscles are adapted to 

 change the position of the axis of the eye with reference to the axis of the 

 orbit, and by the combination of the two sets of muscles, the axis of the 

 eye can be turned with ease and precision to any object in front of the 

 body, 



5, Blood-vessels of the Orbit. The arteries are the ophthalmic artery 

 and its ramifications, assisted by small vessels from the facial, temporal, 

 and internal maxillary arteries. The ophthalmic artery, as the principal, 

 arises from the internal carotid, just after the latter has emerged from the 

 cavernous sinus, and is curving upwards by the side of the anterior clinoid 

 process. It immediately becomes attached to the sheath of the optic nerve, 

 and passing into the orbit, sends ofl' numerous branches to supply the optic 

 apparatus. The principal vein is the ophthalmic, which escapes from the 

 orbit by the inner wide portion of the sphenoid fissure ; it then enters the 

 cavernous sinus, whence the blood is carried by the petrous sinuses to the 

 internal jugular veins. 



6. Nerves of the Eye. The nerves of the eye are large and numerous, 

 no less than four entire nerves and a portion of three others being distributed 

 to this organ. These nerves are the second, third, fourth, and sixth ; one 

 division of the fifth, and branches of the seventh or facial, and of the sympa- 

 thetic. Each of the cerebral nerves arises from a distinct part of the ner- 

 vous system, and ministers to some distinct and special purpose. 



PI. 131, Jig. 1, well formed left eye of a middle-aged man, seen from the 

 front: a h c, eye-brow ; d, upper eye-lid ; e r w, palpebral fissure ; efg h i, 

 inner canthus of the e3'^e, with the lacus and the lachrymal caruncle ; k I, line 

 showing the difierence in height between the two canthi of the eye ; mto q, 

 lower eye-lid ; r, outer canthus ; s t v w, iris. Fig. 2, female eye, for com- 

 ])arison with the male. Fig. 39, lateral view of the eye. Fig. 3, left eye, 

 as shown during a quiet sleep ; a b c^ eye-brow ; od el, depressed upper eye- 

 lid ; e/, completely closed rima; g, lashes of both lids; h to o, translucent 

 portion of the eye-lid ; p, fold of the lower eye-lid. Fig. 4, eye-lids removed, 

 and seen fiom behind : a, portion of the orbicularis muscle ; b, rima palpe- 

 872 



