108 INNERVATION. [CHAP. XIX. 



suffers to such an extent that it becomes reduced to a mere inert 

 membrane, and flaps to and fro as the patient speaks, interfering to 

 a great degree with the clearness of his articulation. 



That the facial nerve in some degree influences the movements of 

 the soft palate, has been suggested by the record of cases in which 

 palsy of the muscles on one side of the face has been accompanied 

 by paralysis of the corresponding half of the velum. That this 

 symptom sometimes accompanies the other signs of this form of 

 palsy, cannot be doubted ; but the frequency of its absence is sufficient 

 to denote the trifling influence of the nerve upon the palatine 

 muscles. Valentin irritated the greater superficial petrosal nerve, 

 which is the probable source of any nervous filaments from the facial 

 to the muscles of the palate, but failed to excite any movement of 

 those muscles in fifteen experiments. 



Much uncertainty exists likewise as regards the function of the 

 chorda tympani. Regarding it, as we do, as a branch of the portio 

 dura, we think it must exercise a motor influence upon the parts to 

 which it is distributed, of which the principal is the duct of the 

 submaxillary gland. But the curious relation which it bears to the 

 malleus and incus denotes that it may have something to do with 

 the mechanism of the organ of hearing. 



It has been made a question how far the facial nerve possesses 

 any sensibility, and from whence it derives sensitive fibres. That 

 irritation of it causes pain, has been sufficiently proved by various 

 experimenters, and it appears that the sensibility is more marked 

 after the nerve has passed through the parotid gland. The sources 

 of the sensitive fibres appear to be clearly indicated by the various 

 anastomoses which the facial nerve forms in its several stages in 

 the Fallopian aqueduct with the vagus nerve, in the face with the 

 fifth nerve, and in the neck with spinal nerves; the communications 

 with the fifth nerve being very numerous. There are therefore suf- 

 ficient means of communication with sensitive nerves to explain the 

 sensibility of the facial without its being necessary to have recourse 

 to the theory of Arnold, and to rank it with the double-rooted nerves. 



Of the Ninth or Hypo-glossal Nerve. The origin of this nerve is 

 from the side of the medulla oblongata along the anterior margin of 

 the olivary body. Ten or twelve fasciculi of fibres emerge here from 

 the central part of the medulla oblongata, and unite into two bun- 

 dles, which coalesce and emerge as one nerve through the anterior 

 condyloid foramen. 



The ninth nerve, on escaping from the anterior condyloid fora- 

 men, passes outwards, and winds forwards around the pharynx, to 





