144 PRACTICAL ZOOLOGY. 



THE MUSCLES OF THE EYEBALL. 



With bone-forceps, or a strong knife, cut away the bone 

 at the outer angle of the eye-socket of the rabbit (almost 

 any mammal will serve for this, though the bone is so 

 thick in the calf or sheep that it will be difficult work 

 without the aid of a good pair of bone-forceps). 



1. With scissors trim away the white membrane around 

 the front of the white of the eye ; this was continuous 

 with the lining of the eyelid, and is the conjunc- 

 tiva. 



2. Find a muscle running along the roof of the eye- 

 socket, which passes through a loop of tendon, near 

 the edge of the orbit, and turns outward to its attach- 

 ment to the top of the eyeball. This is the superior 

 oblique muscle. 



3. Beneath the eye find a muscle, having its origin in 

 the inner front part of the socket, and passing out- 

 ward to be inserted in the lower surface of the eye- 

 ball; this is the inferior oblique muscle. 



4. Four straight muscles, the inferior, superior, internal, 

 and external recti, are attached to the top, bottom, 

 and sides of the eyeball ; find the origin of these, with 

 that of the superior oblique, at the posterior extrem- 

 ity of the eye-socket. 



5. Dissect away the fat and other tissue around these 

 muscles, and find a cone-shaped muscle attached to 

 the back of the eye. Within this find the cylindrical 

 optic nerve. 



