DISSECTION OF THE HEAD AND NECK. 



209 



number of ducts which open on the ocular surface of the upper eyelid, 

 close to the temporal canthus. The gland is to be removed. 



The Levator PALPEBRiE Superioris is described at page 175. 



The Membrana Nictitans and its connection with the adipose tissue 

 of the cavity are described at page 173. 



Fig. 22. 



Muscles of the Eyeball. 

 1, 1. Superior oblique ; 2. Fibrous loop for the same ; 3. Superior rectus ; 4. Internal rectus ; 

 5. External rectus ; 6. Inferior rectus ; 7, 7, 7. Fasciculi of the retractor ; 8. Cut origin of the levator 

 of the upper eyelid ; 9. Nerve to inferior oblique. 



Muscles of the Eyeball. — These are seven in number, viz., four recti, 

 one retractor, and two oblique. (A third oblique muscle was described 

 by the late Professor Strangeways, of the Dick Veterinary College, but 

 its presence is, to say the least, not constant.) 



Directions. — The muscles are to be defined by detaching the eyelids 

 and conjunctiva from the front of the eye, and removing the levator 

 palpebroe and the loose fat which forms a packing material between the 

 muscles. Special care must be taken not to injure the fibrous arch for 

 the tendon of the superior oblique at the inner side of the orbit. 



The Recti. There are four of these, distinguished as the siq^erior 

 rectus, the inferior rectus, the external rectus, and the internal rectus. 

 They ai-e placed one above, one below, and one on either side of, the eye. 

 They have all a flat riband-like form, and are terminated anteriorly by 

 aponeurotic tendons. They all take origin around the optic foramen, 

 and each becomes inserted into the forepart of the sclerotic. 



The Retractor Oculi is placed within the recti, and around the 



