THE CRANIAL, NERVES. 



469 



trigeminus, though the facial remain uninjured, but, according to both 

 Magendie and Bernard, the trunk of the facial, when irritated at its 

 source within the cranial cavity, exhibits no sign of sensibility, although 

 that of the fifth pair may be at the same time perfectly manifest. On 

 the other hand, Chauveau has found that in the recently killed animal, 

 galvanization of the intracranial portion of the facial nerve causes con- 

 traction of the muscles of the face and of the external ear. The nerve 

 is accordingly, at its source, excitable, but insensible. 



FIG. 124. 



DIAGRAM OF THE FACIAL NERVE AND ITS DISTRIBUTION. 1. Facial nerve at its entrance into the 

 internal auditory rueatus. 2. Its exit, at the stylomastoid foramen. 3, 4. Temporal and posterior 

 auricular branches, distributed to the muscles of the external ear and to the occipitalis. 5. 

 Branches to the frontalis muscle. 6. Branches to the stylohyoid and digastric muscles. 7. Branches 

 to the upper part of the platysma myoides. 8. Branch of communication with the superficial 

 cervical nerve of the cervical plexus. 



Furthermore, the most decisive results are obtained from division of 

 the facial nerve at various parts of its course. This may be done, in 

 quadrupeds, at its point of exit from the stylomastoid foramen, or, 

 as practised by Bernard, during its passage through the aqueduct of 

 Fallopius, by a cutting instrument introduced into the cavity of the 

 tympanum, and reaching the nerve through its upper wall. This sec- 

 tion paralyzes all the superficial muscles of the face on the corresponding 



