Q8 THE ANATOMY OF VERTEBEATED ANIMALS. 



muscles, and ultimately divides into two branches, one of 

 which is in relation with the mandibular, and the other with 

 the hyoidean arch. 



The five nerves which have just been mentioned are often 

 intimately connected together. Thus, in the Lepidosiren, the 

 three motor nerves of the eyeball are completely fused with 

 the ophthalmic division of the fifth.* In the Myxinoid fishes 

 there are no motor nerves of the eyeball ; but, in the Lamprey, 

 the rectus externus and inferior, and the obliqutcs inferior, are 

 supplied by the ophthalmic, vs^hile the oculomotor and the pa- 

 thetic unite into a common trunk, which gives branches to the 

 rectus superior and interims, and ohliquus superior. The ocu- 

 lomotor, the pathetic, and the abducens, are more or less con- 

 founded with the ophthalmic in the Amphibia • but in Tele- 

 ostei, Ganoiclei, Elasmohranchii , and in all the higher Yerte- 

 hriita, the nerves of the muscles of the eye are distinct from 

 the fifth pair, except where the oculomotor unites with the 

 ophthalmic into the ciliary ganglion. 



The facial and the trigeminal nerves have common roots 

 in fishes. In Amphibia, though the roots are distinct, the 

 facial may be completely united with the ganglion of the tri- 

 geminal, as in the Frog. In all abranchiate Vertebrata the 

 two nerves are quite distinct. 



Whether the nerves are distinct or not, a, palatine, or vidi- 

 an, nerve (which, in the higher Vertebrata, is especially con- 

 nected with the facial), runs through, or beneath, the base of 

 the skull, parallel with its long axis ; and, after uniting with 

 the superior maxillary, and usually contributing to form the 

 sphenopcdatine, or Mechelian, ganglion, is distributed to the 

 mucous membrane of the roof of the mouth ; and the mandib- 

 ular division of the seventh, or chorda tymp>ani, unites with 

 the inferior maxillary division of the fifth nerve. 



The eighth, pair [auditorii) is formed by the nerves of the 

 orgfan of hearinof. 



The ninth pair {glossophanjii r/ei) is especially distributed to 

 the pharyngeal and lingual regions of the alimentary canal, 

 and, primarily, supplies the boundaries of the second visceral 

 cleft. 



The tenth pair {^pneumocja s^trijd or vagi) consists of very 



•I am greatly disposed to tliink that the motor nerves of the eye more 

 nearly retain their primary relations \tx Lepidosiren than in any other verte- 

 brated animal ; and tliat they are really the motor portions of tlie nerves of 

 the orhito-nasal cleft, the third and fourth appertaining to the inner division 

 of the ophthalmic, the sixtli to its outer division. 



