124 ANATOMY OF THE RABBIT 



root is a motor nerve and joins branch a. Thus the mandibular 

 branch (a) of the trigeminal is both sensory and motor, while 

 the other two branches of this nerve (b. and c.) are sensory. 

 Thus, it is a mixed (motor and sensory) nerve and also has 

 the most varied distribution of any of the cranial nerves. 

 Therefore, it is hoped that dissection of the fifth and seventh 

 will serve to illustrate the principles of functional anatomy 

 of the other ten cranial nerves. The student may dissect 

 all the cranial nerves if he so desires, but this will probably 

 require another rabbit. 



a. Mandibular or third branch: Sends branches to the 

 muscles of mastication, tongue, and other structures, and 

 enters the mandibular ramus through the mandibular (inferior 

 dental) foramen, courses through the ramus, sending branches 

 to the pulp cavities and alveoli of the lower teeth, and emerges 

 through the mental foramina (Fig. 3). 



b. Maxillary or second branch: Sends branches to the upper 

 teeth, palate, and infraorbital nerve through the infraorbital 

 foramen (Fig. 2, IF) to upper lip and part of face, and lower 

 eyelid. 



c. Ophthalmic or first branch : Sends branches to the upper 

 eyelid, lining and end of nose, eyeball, and other structures 

 within and around the orbit. 



Method: Push the facial nerve ventrad out of the way, locate 

 the zygomatic arch, and using the point of the bone cutters, 

 snip through the cranial end of this arch (malar bone) close to 

 the maxillary bone, then through the caudal end of this arch 

 (zygomatic process of temporal bone) close to the mandibular 

 articulation. Loosen the medial side of the arch with a scalpel 

 and then work it under the seventh nerve and turn the excised 

 zygomatic arch, with the attached portion of the masseter 

 muscle, laterad and well down onto the mandible. Note a 

 nerve entering the masseter muscle. With the handle of the 

 cartilage knife, carefully remove this muscle so as to expose 

 the ascending ramus of the mandible. Cut the ascending 

 ramus off with the point of the bone cutters, using great care 



