CHAPTER XIX 

 THE EYE AND THE SENSE OF SIGHT 



Protection and Movements of the Eyeball. The 

 eyeball is a completely closed globular organ lying in the bony 

 cavity of the orbit, the walls of which protect it, except in front, 

 where it is guarded by the eyelids. These latter consist of a 



C./i. 



FIG. 93. 



A. The muscles of the right eyeball viewed from above. 

 H. The muscles of the left eyeball viewed from the outer side. 

 S.R, superior rectus ; In/.K, inferior reel us : E.R, external rectus; S.O6, superior 



oblique; Inf.Ob, inferior oblique; ff, the optic nerves; eft, their crossing or 



chiasma ; ///, the third cranial nerve. 



sheet of dense fibrous connective tissue covered on the outer side 

 by skin, and on the inner side by a membrane with a stratified 

 epithelium, like the epidermis of the skin, but much thinner, 

 called the conjunctiva. At the base of the eyelids the 

 conjunctiva passes on to the eyeball, and, firmly attached to 



