MUSCLES OF EYEBALL. 301 



A model of the eye should also be used in connection with 

 the dissection, but it alone will not make the structure clear. 



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 Conjunctiva. 



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 backward and outward to its attachment 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 outward, to be 

 inserted in the lower surface of the eyeball. This is the Infe- 

 rior Oblique Muscle. 



4. Four straight muscles, the Superior, Inferior, Internal, 

 and External Recti, are attached to the top, bottom, and sides 

 of the eyeball ; find the origin of these, with that of the supe- 

 rior oblique, at the posterior extremity of the eye-socket. 



5. Dissect away these muscles with any fat or other tissue, 

 and find, extending from the back of the eye, the cylindrical 

 Optic Nerve. 



External Parts of the Eye. The eye of the rabbit may 

 be used, but that of the ox is better. 



1. Observe the clear front part of the eye, the Cornea. 

 Note its shape. Its wider end was at the inner angle of the 

 eyelids. 



2. Around the cornea find a whitish membrane, the Con- 

 junctiva, which, a short distance back from the cornea, sepa- 

 rates from the eyeball to turn forward and line the eyelid. 



