66 The Cranial Nerves 



is to say, there is paralysis of the face muscles upon the side of the 

 lesion, with hemiplegia upon the opposite side of the body. 



When cerebral haemorrhage, for instance, occurs within the anterior 

 part of the pons, the decussating fibres of the facial nerve are damaged, 

 together with fibres from the motor area which are passing down to 

 the crossing of the pyramids, and so facial paralysis is, like the hemi- 

 plegia, upon the side of the body opposite to the lesion. But when 

 the clot is formed in the lower part of the pons, the facial nerve upon 

 the side of the lesion is paralysed, whilst hemiplegia still occurs upon 

 the opposite side. ' Such clinical facts as these indicate that some of 

 the deep fibres of the facial nerve pass upward into the cerebrum.' 

 (Ranney.) Before the function of the portio dura was understood, Sir 

 Charles Bell once divided it for facial neuralgia ; its function was 

 thus at once manifested ; and, out of compliment to this experimental 

 physiologist, the peripheral effect of lesion of this nerve is called 

 Bell's paralysis. 



In its course through the petrous bone the nerve gives off the 

 great petrosal branch, which runs in the Vidian as the motor root to 

 Meckel's ganglion, and so to the muscles of the soft palate. The facial 

 also gives off the chorda tympani, which passes across the upper part 

 of the membrana to leave the tympanic cavity by the Glaserian fissure. 

 This slender branch supplies the transverse lingualis, which narrows 

 and protrudes its own side of the tongue. When, therefore, the facial 

 nerve is damaged in the aqueduct, that side of the tongue cannot be 

 narrowed, and consequently, when, in protruding the tongue, the 

 opposite lingualis contracts, the paralysed side cannot advance in due 

 proportion, and so the tip of the tongue is pulled over to that side. 



The chorda eventually joins the gustatoiy nerve (p. 63), and is 

 closely concerned with the sense of taste, perhaps through its associa- 

 tion with the submaxillary ganglion and gland. 



Outside the stylo-mastoid foramen the facial nerve gives off the 

 posterior auricular branch for the hindermost of the muscles of facial 

 expression, namely the posterior belly of the occipito-frontalis and the 

 retraherts aurem. The main trunk then supplies the posterior belly of 

 the digastric and the stylo-hyoid. 



The temporo-facial division, emerging from the parotid gland, 

 crosses the external carotid artery and breaks up into temporal, malar, 

 and infra-orbital branches. The temporal branches supply the attra- 

 hens and attollens aurem and the anterior belly of the occipito-frontalis, 

 the upper part of the orbicularis palpebrarum, and the corrugator. The 

 malar branches also send twigs to the orbicularis, and the infra- 

 orbital supply the buccinator and orbicularis oris, and the neighbour- 

 ing muscles of lips and nostrils. 



The cervico-facial division breaks up into buccal and supra- and 

 infra-maxillary branches. The buccal branches cross the masseter to 

 supply the buccinator and orbicularis. 



