9G 



EVOLUTION OF THE HUMAN EYE 



Fig. 22. — Eye of an antelope showing the retractor bulbi or choanoid 

 muscle (O- S, sheath of Tenon's capsule external to choanoid. R, external 

 rectus. 0, superior oblique. T, Tenon's capsule. 



Fir.. 215. 



-Section through Gegenbauer's muscle from the inner surface. <>f 

 the cornea of a sheep. 



