IX.] 



THE NERVOUS SYSTEM. 



397 



the muscles of the mouth, nose, and eyelids, and to the skin 

 of the neck ; it also sends a long and slender branch to the stylo- 

 hyoid muscle. The other part, called the chorda tympani, 

 comes out at the inner side of the Glasserian fissure, skirts 

 the processus gracilis of the malleus, and runs along within 

 the mandible to the sub-maxillary ganglion, in close juxtapo- 

 sition with a branch of the third division of the fifth nerve. 



These relations are constant, so that the seventh nerve 

 divides into two branches, which respectively go to the anterior 

 and posterior boundaries of that visceral cleft which divides 

 the mandibular and hyoidean arches. In some of the lower 

 Vertebrates the fifth and seventh nerves are much blended, 

 and the two may, as in the Frog, be completely united at the 

 large ganglion at the root of the former. 



25. The EIGHTH NERVE is a very complex structure, and 

 consists of at least three nerves united together, and all 

 arising from the medulla oblongata and passing out by the 

 jugular foramen. 



The first of these, called the glosso-pharyngeal, supplies 



FIG. 349. NERVOUS SUPPLY OF THE HINDER PART OF THE RIGHT SIDE OF 



THE HEAD OF THE SHARK Hexanckus gnseus. 



(After Haeckel.) 



/, palato- quadrate arch ; h t proximal part of the hyoidean arch ; & 1 3 6 , six 

 branchial arches; 15, proximal parts of the branchial arches; m, spinal 

 marrow ;f, facial nerve ; t^, inferior maxillary (or third) branch of fifth nerve ; 

 g, glosso-pharyngeal ; tn, mandibular division of facial nerve ; hy, hyoidean 

 division of the glosso-pharyngeal ; vg, nervus vagus ; /, nervus lateralis ; 

 sp, spinal nerves. 



