THE ORBIT 315 



(a) The levator palpebrae superioris. Origin: Wall of the 

 orbit above the optic foramen. Insertion: Upper eyelid. 

 This thin sheet of muscle should be separated from the 

 underlying rectus superior of the eyeball. 



{b) The obliquus superior. Origin: Anterior margin of the 

 optic foramen. The muscle passes upward on the wall of 

 the orbit, then beneath a fibrous cord, the trochlea, which 

 bridges a small portion of the orbital wall and changes the 

 course of the tendon by a considerable angle. Insertion: 

 Anterodorsal portion of the eyeball. 



(c) The obliquus inferior. Origin: Lacrimal bone. Insertion: 

 Posteroventral portion of the eyeball. 



The oblique muscles are relatively large in the rabbit, 

 a feature correlated with the lateral direction of the eyes. 



(d) The four recti muscles, superior, inferior, medialis, and 

 lateralis, arise from the boundary of the optic foramen, 

 and are inserted respectively on the dorsal, ventral, anterior, 

 and posterior portions of the periphery of the eyeball. 



{e) The retractor oculi, or retractor bulbi, muscle (best seen 

 after removal of the eye) originates on the posterolateral 

 margin of the optic foramen, internal to the origin of the 

 lateral rectus muscle, and is connected by a fibrous band 

 through the foramen with the origin of the corresponding 

 muscle of the other side. It has the form of a hollow cone 

 with a cleft along its dorsal wall, in w^hich the optic nerve 

 lies upon a bed of fatty connective tissue. It is inserted on 

 the medial portion of the eyeball around the optic nerve. 

 Although the retractor oculi is described as consisting of 

 four distinct parts, these are fused in the rabbit so that 

 they are indicated only by sinuosities in the line of insertion 

 alternating with the insertions of the recti muscles. 



(/) The Harderian gland (gl. Harderiana) is a large, compact, 

 lobulated gland lying in the anterior portion of the orbit, 

 internal to the inferior oblique muscle. It is composed, in 

 the rabbit and the hare, of two parts, a large, pale, grey- 

 reddish, posteroventral lobe and an almost white antero- 

 dorsal lobe about one-third the size of the former. Both 



