MUSCLES OF THE ORBIT. 643 



ophthalmic trunk will appear. The lachrymal nerve may remain 

 uncut. 



The LEVATOR PALPEBfLE SUPERIORIS (fig. 227, B) IS the most super- Elevator of 



ficial muscle, and is attached posteriorly to the roof of the orbit in 

 front of the optic foramen. The muscle widens in front, and bends 

 dowmvards in the upper eyelid to be mainly inserted by a broad attached to 

 tendon into the front of the tarsal plate. Expansions from the tendon 

 can be traced to the tissues over the eyebrow and at the root of the 

 upper lid. 



By one surface the muscle is in contact with the frontal nerve relations; 

 and the periosteum ; and by the other with the superior rectus 

 muscle. If it is cut across about the middle,' a small branch of the 

 third nerve will be seen entering the posterior half on the under 

 surface. 



Action. The lid is made to glide upwards over the ball by this use. 

 muscle, so that the upper edge is directed back and the lower 

 forwards, the skin above the lid being folded inwards at the same 

 time. 



The SUPERIOR RECTUS (fig. 227, D) is the upper of four muscles Upper rec- 

 that lie around the globe of the eye. It arises from the upper tu 

 part of the optic foramen, and is connected with the other recti r 

 muscles around the optic nerve. In front the fleshy fibres end in insertion ; 

 a tendon, which is inserted, like the other recti, into the sclerotic 

 coat of the eyeball about a quarter of an inch behind the transparent 

 cornea. 



The under surface of the muscle is in contact with the globe of the position to 

 eye, and with some vessels and nerves to be afterwards seen ; the 

 tipper surface is partly covered by the preceding muscle. The action use. 

 of the muscle will be given with the other recti (p. 650). 



The SUPERIOR OBLIQUE MUSCLE (fig. 227, A) is thin and narrow, upper 

 and passes through a h'bro-cartilaginous loop at the inner angle of obll( i ue 

 the orbit before reaching the eyeball. The muscle arises behind 

 from the upper and inner part of the optic foramen, and ends 

 anteriorly in a rounded tendon, which, after passing through the loop, 

 or pulley, referred to, is reflected backwards and outwards between traverses a 

 the superior rectus and the globe of the eye to be inserted into the pl 

 sclerotic coat behind the middle of the ball. 



The fourth nerve is supplied to the orbital surface of the muscle relations: 

 and the nasal nerve lies below it. The thin insertion of the muscle 

 lies between the superior and the external recti, and near the tendon 

 of the inferior oblique. 



The pulley, or trochlea (fig. 228, p. 645), is a fibro-cartilaginous ring pulley of 

 about one-sixth of an inch wide, which is attached by fibrous tissue 

 to the depression of the frontal bone at the inner angle of the orbit. 

 A fibrous layer is prolonged from the margin of the pulley on to 

 the tendon ; and a synovial sheath lines the ring, to facilitate the 

 movement of the tendon through it. To see the synovial sheath 

 and the free motion of the tendon, this prolongation may be cut 

 away. 



T T 2 



