518 ANATOMICAL TECHNOLOGY. 



tion at the caudal margin of the white zone as with the lateral rec- 

 tus (Fig. 126). 



1408. M. rectus dorsalis (superior), (Fig. 126, M. r. drsl.). 

 Cut for about 1 cm., close to the bone, the fibrous band holding 

 the eyeball to the postorbital process of the frontal. Draw the eye- 

 ball cephalad, and the dorsal rectus will appear on the dorsal side 

 of the eyeball. Dissect it as described for the others ( 1405), and 

 note that its insertion is at the same level on the eyeball, as shown 

 in Fig. 126. 



A considerable band passes from the ventral rectus to the Mem- 

 brana nictitans. This is composed mostly of connective tissue, but 

 with the microscope a small number of muscular fibers may be 

 found in it. It is thus a retractor of the Membrana nictitans. 



1409. M. levator palpebrae dorsalis (superior! s). This very 

 thin, slender muscle may be seen by grasping some of the fibrous 

 substance near the cornea and drawing the ball cephalo-ventrad. 

 It is on the ectal surface of the dorsal rectus for the first fourth of 

 its length, then it inclines mesad. Isolate it with the greatest care. 

 About opposite the point of insertion it spreads out into a broad 

 tendon, which is attached to the dorsal lid (Fig. 126). Grasp the 

 edge of the dorsal lid and raise it from the ball ; then pull upon the 

 muscle, and the traction can be seen on the ental surface of the lid. 



1410. M. rectus mesalis (internus). --Divide the ventral 

 oblique and sever the fibrous connection of the eyeball with the 

 orbital fossa on the ventral side to a point about opposite the open- 

 ing of the lachrymal canal on the dorsal lid ; then evert the Mem- 

 brana nictitans and draw the eyeball laterad. This will expose the 

 mesal rectus. Its attachment to the eyeball should be determined 

 as described in 1405. 



1411. M. trochlearis s. obliquus dorsalis (superior). This 

 muscle will appear mesad of the rectus mesalis. Draw the eyeball 

 caudad and laterad and isolate the muscle from its origin toward its 

 insertion. When about opposite the middle of the eyeball, it 

 merges into a slender tendon which extends to a point a little cau- 

 dad and entad of the mesal canthus, where it passes through a 

 fibro-cartilaginous ring. This ring is held somewhat loosely to the 

 bony orbit, nearly directly opposite the origin of the ventral 

 oblique, by a strong fibrous band about 4 mm. long extending 

 directly dorsad, and a slender one about 25 mm. long attached to 



