212 MANUAL OF ANIMAL BIOLOGY 



5. Trigeminal Nerves. This is a large and important pair of 

 cranial nerves. Each trigeminal nerve arises by two roots from the 

 side and near the anterior end of the medulla. The two roots 

 unite to form a prootic ganglion from which arises the trigem- 

 inal nerve proper. Each prootic ganglion marks the origin also 

 of an autonomic nerve trunk. Each trigeminal nerve soon 

 branches into two parts : (a) the ophthalmic and (b) the maxillo- 

 mandirular. The latter divides again into two branches : (i) the 

 superior maxillaris and (ii) the mandibular. The various 

 branches of the trigeminal nerves innervate considerable portions 

 of the facial region, more particularly around the mouth, the 

 tongue, and the muscles of the lower jaw. (W. f. 142, Vg.) 



6. Abducens Nerves. This pair arises from the ventral side of 

 the medulla, close to and on either side of the mid- ventral line. 

 Each nerve is distributed to certain muscles of the eye and also 

 connects with a prootic ganglion. 



7. Facial Nerves. This pair arises from the medulla just pos- 

 terior to the trigeminal nerves. Each facial nerve divides into 

 two main branches : (a) the palatine and (6) the hyomandibular. 

 This nerve has a wide distribution to various parts of the face, nose, 

 and throat. Each also connects with a prootic ganglion. 



8. A uditory Nerves. These arise from the medulla just posterior 

 to the facial (7) and run laterally on either side to innervate the 

 inner ear. 



9. Glossopharyngeal Nerves. These arise from the medulla 

 posterior to the auditory (8) and together with the fibers of the 

 vagus (10). They innervate certain muscles and lining mem- 

 branes of the tongue and pharynx. 



10. Vagus Nerves. These arise, as has been noted, in common 

 with the glossopharyngeal (9). Each of the vagus nerves has two 

 branches, the anterior one (ramus auricularis) being much 

 smaller. It runs forward and is distributed to the region of the 

 tympanum of the ear. The main branch of the vagus runs pos- 

 teriorly and gives off a number of small branches which innervate 

 the muscles of the shoulder. The remainder of the posterior 

 branch of this nerve is distributed to some of the important vis- 

 ceral organs, such as the esophagus, stomach, lungs, and heart. 

 (W. f. 142, Xg.) 



In the higher Vertebrates, two other pairs of cranial nerves are 

 present: the spinal accessory (11) and the hypoglossal (12), 



