NERVE 201 



partly of anterior root fibres. The vagus is the great 

 ingoing nerve from tiic abdomen, thorax, larynx, and gullet, 

 while, by outgoing fibres, passing through it or through the 

 accessorius, it is augmentor for the muscles of the bronchi 

 and alimentary canal, inhibitory to the heart, dilator to 

 blood-vessels of the thorax and abdomen, and motor to the 

 muscles of the larynx and to the levator palati. The 

 accessorius is also motor to the sterno-cleido-mastoid and 

 trapezius. 



The IX. (Glossopharyngeus) is essentially a posterior 

 root, and is the ingoing nerve for the back of the mouth, 

 the Eustachian tube, and tympanic cavity. It also contains 

 outgoing somatic fibres to the stylo-pharyngeus and middle 

 constrictor of the pharynx, and outgoing visceral fibres 

 which are secretory and vaso-dilator to the parotid gland. 



The VII. (Facial) is almost purely an anterior root, trans- 

 mitting somatic motor fibres to the muscles of expression 

 and to the stapedius muscle, visceral secretory fibres to the 

 submaxillary and sublingual glands and the glands of the 

 mouth, and vaso-dilator fibres. It also carries ingoing 

 fibres from the anterior two-thirds of the tongue. It is the 

 cranial nerve most frequently paralysed, and this condition 

 is often caused by inflammatory changes in the canalis 

 facialis in which it passes through the temporal bone. The 

 condition in man is known as BeWs 'paralysis. It occurs in 

 the horse, and it is characterised by a drooping of the ear 

 on the afi'ected side, by the upper eyelid being pulled to the 

 middle line, while the lower eyelid droops, by an elongation 

 of the nostril and difficulty of breathing through it, and by 

 a pendulous condition of the lips so that saliva and food 

 dribble from the mouth. 



The V. (Trigeminal) is chiefly a posterior root, but it has 



a distinct anterior or motor root which joins it, and it carries 



the motor fibres to the muscles of mastication and to the 



tensor tympani. It is the great ingoing nerve for all the face. 



The VI. (Abducens) supplies the external rectus of the eye. 



The IV. (Trochlears) supplies the superior oblique. 



The III. (Oculo-motorius) supplies all the muscles of the 



eye except those supplied by VI. and IV. 



