THE CAT 251 



the external ear, where it gives off branches which supply the 

 muscles of the face. The auditory is a large nerve just behind 

 the facial, passing directly to the inner ear. 



In exposing the remaining cranial nerves take great care not to 

 break them, as they arise by fine roots which are easily injured. 



The ninth and tenth cranial nerves, the glossopharyngeal and 

 the vagus, arise from the side of the medulla back of the auditory 

 nerve, each by a number of small roots, and leave the cranial 

 cavity together immediately behind the tympanic bulla. The 

 glossopharyngeal passes backward and sends branches to the 

 pharynx and tongue ; it is the sensory nerve of the tongue. 



The vagus passes along the neck on each side, bound together 

 with the sympathetic nerve, giving off branches to the pharynx 

 and larynx. Two ganglia, the ganglion jugulare and the ganglion 

 nodulosum, are present in it near the point where it leaves the 

 cranial cavity, the former ganglion being in front of the latter. 



At the hinder end of the neck the vagus and the sympathetic 

 separate from each other and enter the thorax. The former, 

 which is the larger of the two, soon gives off the inferior laryngeal 

 nerve, which runs forward alongside the trachea to the larynx. 

 The vagus then passes to the anterior end of the lung, where it 

 breaks into numerous branches, which form networks at the base 

 of the lungs and heart, called the pulmonary plexus and the cardiac 

 plexus respectively. Two branches pass back, on each side, to the 

 stomach, forming the anterior and posterior gastric plexuses. 



The spinal accessory, the eleventh cranial nerve, is formed by 

 the union of numerous roots which arise along the lateral surface 

 of the medulla and spinal cord. It passes with the spinal cord 

 into the cranium through the foramen magnum, and then out 

 again together with the vagus and glossopharyngeal nerves; it 

 supplies the muscles of the neck.- 



The hypoglossal, the twelfth cranial nerve, arises from the 

 ventral surface of the medulla by a number of roots. It passes 

 from the cranial cavity to the muscles of the neck and tongue; 

 it is the motor nerve of the tongue. 



Exercise 39. Draw a semidiagrammatic view of the lateral aspect of 

 the brain, showing the cranial nerves so far as observed. 



