COMPARATIVE ANATOMY OF THE NERVOUS SYSTEM 345 



Besides the branches of the mandibular nerve here named there are branches 

 to the muscles of mastication, namely, the temporal, the masseter, the anterior 

 part of the digastric, and the pterygoids. 



Remove the half of the mandible. This will reveal additional branches of 

 the mandibular nerve. One of these, the buccinator, will probably be noticed 

 extending to the angle of the mouth, where it supplies the masseter muscle and 

 the lips. The main trunk of the maxillary nerve, the second branch of the 

 trigeminus, may now be sought. It is a very stout trunk lying at the sides of 

 the palate in front of and more deeply situated than the main trunk of the man- 

 dibular nerve. It is somewhat concealed by an artery (internal maxillary) which 

 runs along its ventral surface and should be removed. The maxillary nerve is then 

 revealed as a large trunk which passes forward along the side of the hard palate 

 and disappears dorsal to the teeth. Cut away the zygomatic arch on the same 

 side on which the half of the mandible was removed; in the rabbit cut away 

 also the ridge which holds the molar and premolar teeth. By this operation 

 the contents of the orbit are revealed. Note in the cat the small reddish infra- 

 orbital salivary gland lying close to the maxillary nerve. In the rabbit the very 

 large reddish mass of the Harderian gland with the smaller yellowish mass of 

 the infraorbital salivary gland anterior to it are readily noticed. The maxillary 

 nerve should now be investigated. It is seen to divide into a large main trunk, 

 the infraorbital nerves, and a small medial branch, the spheno palatine nerve, 

 which passes into the hard palate. The infraorbital nerves pass forward above 

 the teeth, which they supply, and emerge through the infraorbital foramen, 

 situated internal to the root of the zygomatic arch. On separating the upper 

 lip from the teeth the foramen is readily found and the nerve is seen emerging 

 from it to supply the upper lip and side of the nose. Follow the sphenopalatine 

 nerve toward the palate, cutting away the bone. It connects with a ganglion, 

 the sphenopalatine ganglion of the sympathetic system. This ganglion lies near 

 the sphenopalatine foramen. The chief branch of the sphenopalatine nerve 

 is the palatine branch which passes into the hard palate by a foramen. In the 

 cat this nerve arises before the ganglion is reached, in the rabbit beyond the 

 ganglion. Other branches of the sphenopalatine nerve pass from the ganglion 

 into the nasal cavity. 



4. The sense organs of the head. 



a) The eye, the eye muscles, and the nerves of the orbit: Dissect on the other 

 side from that on which the cranial nerves were worked out. Identify upper 

 and lower eyelids and the nictitating membrane, a fold projecting from the 

 anterior corner of the eye. Make a slit through the junction of upper and lower 

 lids at the posterior corner of the eye so that the eyelids can be pulled away 

 from the eyeball. Note that the skin passes onto the inner surface of the eyelids 

 and continues over the exposed surface of the eyeball, thus forming the outer- 

 most covering membrane, the conjunctiva, for this part of the eyeball. Make an 



