222 ANIMAL BIOLOGY. [Parti. 



V. Trigeminal ; arising from the myelencephalon, and, just 

 before leaving- the skull, expanding into a Gasserian ganglion. 

 Outside the skull each divides into an anterior orbito-nasal 

 branch, passing to the nasal capsule and integument in its 

 neighbourhood, and a maxillo-mandibular branch which shortly 

 divides into a maxillary branch which supplies the upper jaw 

 and lower eyelid, and a mandibular branch which supplies 

 the lower lip and muscles of the floor of the mouth. 



VI. Abducent; arising from the myelencephalon, entering the 

 Gasserian ganglion, and supplying certain eye-muscles. 



VII. Facial; arising from the myelencephalon and entering 

 into close connection with the Gasserion ganglion. Each leaves 

 the skull just behind the trigeminal, and soon divides into 

 (1) a palatine branch, which runs forward beneath the mucous 

 membrane of the palate ; (2) a hyo-mandibular branch, which 

 passes back over the columella, and down to the angle of the 

 mouth. It then gives rise to two branches ; one, the hyoidean } 

 supplying the muscles of the anterior cornu of the hyoid, the 

 other, the chorda tympani, running along the inner edge of the 

 lower jaw. 



VIII. Auditory ; arising from the myelencephalon, and passing 

 to the organ of .hearing. 



IX. Glosso-pharyngeal ; arising from the myelencephalon. Each 

 leaves the skull by a foramen, just behind the auditory capsule, 

 gives off a branch which joins the hyo-mandibular branch of 

 the facial, and thus passes by a somewhat sinuous course to 

 the base of the tongue. 



X. Pneumogastric or Vagus ; arising from the myelencephalon, 

 and leaving the skull in close company with the glosso-pharyn- 

 geal. Outside the skull each bears a ganglionic swelling. It 

 gives off cutaneous branches to the dorsal integument, and 

 then gives rise to (1) a laryngeal branch, forming a loop over 

 the pulmo-cutaneous artery ; (2) a splanchnic branch ; this sub- 



