54 6 TEXT-BOOK OF PHYSIOLOGY. 



3. The stapedius branch leaves the aqueduct of Fallopius somewhat 



further down by a small foramen, enters the pyramid of the 

 middle ear, and is finally distributed to the stapedius muscle. 



4. The chorda tympani is given off from the facial at a point about 



five millimeters above the stylo-mastoid fdrarrien. It then passes 



upward and forward and enters the tympanum through the iter 



chordae posterius, crosses the tympanic membrane between the 



malleus and incus, leaves the tympanum by the iter chordae 



anterius or canal of Huguier, and finally joins the lingual branch 



of the fifth. Some of its fibers can be traced to the dorsum of 



the tongue, others to the submaxillary and sublingual ganglia, 



where they terminate in tufts around the ganglion cells. 



Properties. Electric stimulation of the trunk of the nerve after 



its emergence 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 intracranial 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, fre- 

 quently 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 compres- 

 sion of the nerve-trunk in any part of its intracranial course. 



The phenomena presented by an individual suffering from division 

 or compression of the facial nerve, and which collectively constitute 

 facial paralysis, are as follows : a relaxed and immobile condition of 

 the side of the face corresponding to the lesion ; separation of the eye- 

 lids from paralysis of the orbicularis palpebrarum and the unopposed 

 contraction of the levator palpebrae muscles; abolition of the act of 

 winking; drooping of the angle of the mouth; an escape of saliva 

 from the mouth; contraction of the muscle and distortion of the 

 opposite side of the face; on attempting to laugh or talk the dis- 

 tortion of the face is increased; during mastication the food accu- 

 mulates between the teeth and cheek, from paralysis of the buccina- 

 tor; articulation is impaired from paralysis of the orbicularis oris 

 muscle, the labial sounds especially being imperfectly produced. 



Properties of the Branches Given off in the Aqueduct of 

 Fallopius. The great petrosal nerve is in all probability composed 

 of efferent fibers (vaso-dilatator and secretor) which leave the pons 

 by way of the nerve of Wrisberg, or pars intermedia, to be distributed 

 around the cells of the spheno-palatine ganglion; for stimulation 

 either of this nerve or of the ganglion is followed by the same results : 

 viz., dilatation of the blood-vessels of, and secretion from, the mucous 



