willard: cranial nerves of anolis carolinensis. 31 



I. MUSCLES. 

 1. Muscles of the Orbit. 



This group includes the muscles of the eyeball proper and those of 

 the eyelid, or their derivatives. The former are the dorsal, ventral, 

 anterior, and posterior recti, and the dorsal and ventral oblique, to- 

 gether with the m. retractor oculi and m. bursalis. Those of the eyeHd 

 consist of the m. depressor palpebrae inferioris and its specialized part, 

 m. protrusor oculi (Bruner). 



Mm. rectus posterior {externus), bursalis, and retractor oculi. Not 

 only in their innervation but also in their skeletal connections, these, 

 muscles form one group, having a more posterior origin than any of 

 the other muscles of the eyeball. The bursalis (brs.) and the retractor 

 oculi {rtr. oc.) arise close together within the basisphenoid bone 

 (Plate 6, fig. 16), that of the bursalis being on the innfr lateral surface 

 of the bony cap containing the distal end of the pituitary body. The 

 area of origin of the fibers of the retractor forms a median forward 

 continuation of that of the bursalis ; the two muscles then run rostrad 

 together into the orbit, where they separate (Plate 5, figs. 14, 1.5). 

 The bursalis fibers bend rather sharply dorsolaterad within the orbit 

 to be inserted on the posterior median side of the eyeball, thus offering 

 a sort of loop through which passes the tendon from the nic'-itating 

 membrane (Plate 5, fig. 14, tnd. mb. nic). 



The retractor oculi passes directly forward across the floor of the 

 orbit as a relatively slender muscle to be inserted on the median side 

 of the eyeball anterior and ventral to the optic nerve (Plate 5, figs. 

 13, 14).^ 



Somewhat anterior to the origin of these the posterior rectus arises 

 from the presphenoid bone (prcsph.) along the median line and passes 

 directly out around the posterior side of the orbit to its insertion on 

 the eyeball (Plate 3, fig. 7 and Plate 5, fig. 15, rt. p.). 



Mm. recti dorsalis and ventralis. These muscles arise at the same 

 cross-section level as the rectus posterior, but dorsal to it, from a 

 median fascia between the presphenoid and a cartilaginous rod which 

 continues forward from the inner lamellae of the basisphenoid bone 

 (Plate 5, fig. 15, rt. d., rt. v.). The one passes dorsal to the optic nerve, 

 the other \entral, and each spreads out into a broad fan-like insertion 

 on the dorsal and ventral sides of eyeball respectively (Plate 5, figs. 

 12, 13). 



