348 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



angle of the orbit is the flattened lacrimal gland. Cut out the nictitating 

 membrane and examine its internal surface. It is found to be roughened, owing 

 to the presence of the Harderian gland in its wall. 



Turn to the ventral surface of the eyeball exposed by the removal of the 

 mandible, the zygomatic arch, and part of the hard palate. Identify again the 

 small reddish infraorbital salivary gland, situated back of the last tooth. On 

 clearing away connective tissue and fat, the inferior oblique eye muscle will be 

 seen extending from the anterior part of the orbit to the ventral surface of the 

 eyeball. Ventral and at right angles to the inferior oblique is the inferior rectus. 

 The branch of the oculomotor which innervates the inferior oblique runs along 

 the posterior border of the inferior rectus. The zygomatic branch of the maxil- 

 lary nerve passes along the posterior border of the inferior rectus to the lower 

 eyelid, but may have been destroyed. Posterior to the inferior rectus is the 

 external rectus; between and internal to them appears one of the four parts of the 

 retractor bulbi muscle. Along the posterior border of the external rectus runs 

 the lacrimal branch of the maxillary nerve, supplying the lacrimal gland and 

 adjacent skin. On detaching the eyeball from the posterior wall of the orbit 

 another part of the retractor bulbi will be seen next posterior to the external 

 rectus; dorsal to this is the superior rectus. Cut through both obliques at their 

 insertions and press the eyeball posteriorly. Note the internal rectus on the 

 anterior surface of the eye and above it the remainder of the retractor bulbi. 



Cut through all of the eye muscles and the optic nerve at their insertion on 

 the eyeball and remove the latter. Note the four parts of the retractor bulbi 

 around the optic nerve. Deflect the external rectus ventrally and note the 

 abducens nerve ascending on its inner surface. Running along the ventral sur- 

 face of the optic nerve note a slender nerve, the long ciliary branch of the oph- 

 thalmic branch of the trigeminus; it accompanies the optic nerve into the 

 eyeball. Look on the inner surface of the inferior rectus for the branch of the 

 oculomotor to this muscle. Note the ciliary ganglion of the sympathetic near 

 this branch and observe branches between this ganglion and the oculomotor 

 and long ciliary nerves and the short ciliary nerves passing from the ganglion 

 along the optic nerve. Find the main trunk of the oculomotor ventral to the 

 optic nerve at the place of passage of both through the wall of the orbit, and 

 note branches of the oculomotor to the retractor bulbi and superior rectus. 

 Bend all eye muscles except the superior oblique ventrally, leaving the superior 

 oblique against the medial wall of the orbit. Crossing the inner surface of the 

 superior oblique obliquely forward are two nerves. They are parts of the oph- 

 thalmic branch of the trigeminus. The lower one is the ethmoidal nerve; it 

 passes through a foramen into the nasal cavity. The upper one is the infra- 

 trochlear nerve. It goes to the anterior part of the upper eyelid. Posterior 

 to and parallel to the posterior margin of the superior oblique is> the frontal 

 branch of the ophthalmic. It innervates the upper eyelid and integument 



