THE PERIPHERAL NERVOUS SYSTEM. 373 
nerve which leaves the caudal angle of the sphenopalatine 
ganglion and passes caudad. It enters the orbital fissure, lying 
in a groove on its ventral wall (the cranial end of this groove 
is sometimes converted into a canal). The groove ends 
caudally in a foramen which pierces the sphenoid bone between 
the wing and the body and lies just mediad of the foramen 
rotundum. The groove and foramen constitute the pterygoid 
canal (from which the nerve is named). After emerging from 
the pterygoid canal onto the ventral surface of the basisphenoid 
the nerve enters the tympanic bulla along with the Eustachian 
tube, lying on the medial side of the latter. Just after enter- 
ing, on reaching the internal carotid artery, it divides into two. 
One of these, N. petrosus superficialis major (p. 375), passes 
into the hiatus facialis of the petrous bone and joins the facial 
nerve. The other, N. petrosus profundus, accompanies the 
internal carotid artery caudad, turning therefore out of the 
bulla and passing caudad along its medial side; it finally joins 
the superior cervical ganglion of the sympathetic system. 
3. N. mandibularis.—The third division of the fifth, the 
mandibular nerve, takes origin by a strong root from the 
semilunar (or Gasserian) ganglion, and receives also after 
separating from the ganglion the ‘smaller ventral root (portio 
minor) of the fifth nerve. The root from the ganglion is sen- 
sory; the smaller root is motor, so that the mandibular nerve 
is both sensory and motor. The nerve passes through the 
foramen ovale, and sends off at once the following branches: 
a. N. auriculotemporalis (Figs. 154 and 155, ).—This 
passes dorsad between the cartilaginous auditory meatus and 
the zygomatic process of the temporal bone (Fig. 154, 7), 
emerges at the caudal border of the masseter muscle (Fig. 
155, 2), and divides into two chief branches. One, the auric- 
ular branch, passes along the cranial side of the external ear 
and is distributed to its integument. The other, the temporal 
branch, passes along the zygomatic arch, gives branches to the 
temporal muscle and to the skin, follows the zygomatic arch 
almost to the angle of the mouth, and anastomoses with the 
superior buccal branch of the facial (Fig. 155, £). 
