THE CRANIAL NERVES. 591 



supercilii, and the upper half of the orbicularis palpebrarum, are derived 

 from the oculo-motor nucleus, and, descending the posterior longitudinal 

 bundle, enter the trunk of the facial as it turns to pass forward through the 

 pons. It is also probable, for similar reasons, that the fibers distributed to 

 the orbicularis oris are derived from the hypoglossal nucleus. 



Cortical Connections. The nucleus of the facial nerve is in histologic 

 and physiologic connection with the facial region of the general motor area 

 of the cerebral cortex. From the cells of this region axons descend through 

 the pyramidal tract, the internal capsule, and the cms cerebri, beyond which 

 they cross to the opposite side and arborize around the cells of the nucleus 

 already described. 



Distribution. From its superficial origin the trunk of the nerve passes 

 into the internal auditory meatus beside the auditory nerve. After passing 

 forward and outward for a short distance through the bone above and be- 

 tween the cochlea and vestibule, the nerve makes a sharp bend, forming the 

 genu facialis, turns backward and enters the aqueduct of Fallopius, the gen- 

 eral course of which it follows as far as the stylo-mastoid foramen. After 

 emerging from this foramen the nerve passes downward and forward as far 

 as the parotid gland, within which it terminates by dividing into two main 

 branches, the temporo-facial and the cervico-facial, the ultimate branches 

 of which are distributed as previously stated to the superficial muscles of the 

 head and face (Fig. 277). 



Properties. Electric stimulation of the trunk of the nerve after its emer- 

 gence from the stylo-mastoid foramen produces convulsive movements in all 

 the muscles to which its branches are distributed. The same results follow 

 stimulation of the intra-cramal portion of the nerve in an animal recently 

 killed. 



Irritative pathologic lesions e.g., tumors, aneurysms, etc. situated 

 along the course of the nerve or at its nuclear origin, frequently give rise to 

 spasmodic movements of the facial muscles which may be tonic or clonic in 

 character. 



Division of the facial nerve after its emergence from the stylo-mastoid 

 foramen is followed by a complete relaxation or paralysis of the superficial 

 facial muscles. The same result follows compression of the nerve-trunk in 

 any part of its intra-cranial course. 



The phenomena presented by an individual suffering from division or 

 compression of the facial nerve, and which collectively constitute facial paraly- 

 sis, are as follows: A relaxed and immobile condition of the side of the 

 face corresponding to the lesion; separation of the eyelids from paralysis of 

 the orbicularis palpebrarum and the unopposed contraction of the levator 

 palpebrae muscles; abolition of the ability to wink; drooping of the angle of 

 the mouth; an escape of saliva from the mouth; contraction of the muscles 

 and distortion of the opposite side of the face; on attempting to laugh 

 or talk the distortion of the face is increased; during mastication the food 

 accumulates between the teeth and cheek, from paralysis of the buccinator; 

 articulation is impaired from paralysis of the orbicularis oris muscle, the 

 labial sounds especially being imperfectly produced. 



Functions. The function of the facial nerve is the transmission of 

 nerve impulses from the nerve-cells in which it arises to the superficial 



