CHAP, vi.] THE BRAIN. 649 



5. Trigeminus. A mixed efferent and afferent nerve, with 

 distinct motor and sensory roots, the latter bearing the ganglion of 

 Gasser. 



Efferent Fibres. Motor fibres to the muscles of mastication, 

 temporal, masseter, two pterygoids (mylo-hyoid, anterior belly of 

 digastric), to the tensor palati, and tensor tympani; vaso-motor 

 fibres to various parts of the head and face ; secretory fibres to the 

 lachrymal gland, and according to some authors to the parotid and 

 submaxillary glands by fibres joining the facial. Trophic (?) 

 fibres to eye, nose, and other parts of the face. Efferent fibres for 

 the dilation of the pupil. 



Afferent Fibres. General nerve of sensation of the skin of 

 head and face, and of the mucous membrane of the mouth, except 

 the back part of the tongue, the posterior pillars of the fauces, and 

 a large part of the pharynx, these parts being supplied by the 

 glossopharyngeal and vagus; the back of the head is chiefly 

 supplied by branches from the cervical nerves, and the external 

 meatus and concha are supplied chiefly by the auricular branch of 

 the vagus. Nerve of special sense of taste for the front part of 

 the tongue. 



6. Abducens. Motor nerve to the rectus externus. When 

 the nerve is divided or otherwise paralysed, the eye is turned 

 inwards. It probably receives recurrent sensory fibres from the fifth. 

 It is also joined by fibres coming from the cervical sympathetic ; 

 when this latter nerve is divided in the neck, the action of the 

 muscle is said to be weakened. 



7. Facial. Motor nerve to the muscles of the face; hence 

 nerve of expression. Supplies also stylohyoid, posterior belly of 

 the digastric, buccinator, stapedius, muscles of the external ear, 

 platysma, some muscles of the palate, viz. the levator palati and 

 probably others. Secretory nerve of submaxillary and parotid 

 gland. Receives afferent, possibly efferent, fibres from trigeminus 

 and also from vagus. It is said by some to contain vaso-motor 

 fibres for the tongue and side of the face. The effects of paralysis 

 of the facial, from the inability of the orbicularis to close the eye, 

 the drawing of the face to the sound side, and the smoothness of 

 the paralysed side, are very striking. 



8. Auditory Nerve. Special nerve of hearing ; afferent nerve 

 for impulses other than auditory proceeding from the semi-circular 

 canals. 



9. Olosso-pharyngeal. Motor nerve for levator palati, azygos 

 uvulae, stylo-pharyngeus, constrictor faucium medius; the motor 

 functions of this nerve have been disputed. Special nerve of taste 

 for the back of the tongue. General nerve of sensation for the 

 root of the tongue, the soft palate, the pharynx (being here 

 associated with the vagus), the Eustachian tube and the tympanum. 



