74 MANUAL OF ELEMENTARY ZOOLOGY 



branch to the lower jaw. The sixth or abducent nerve is 

 very small. It arises from the ventral side of the medulla 

 about the middle of the length of the latter, and supplies 

 the external rectus muscle, after passing through the 

 prootic ganglion. The seventh or facial nerve arises from 

 the side of the medulla behind the fifth. It joins the 

 prootic ganglion. 1 On leaving this it at once divides into a 

 palatine branch, which runs forwards on the floor of the 

 orbit to supply the roof of the mouth, and a hyomandibular 



Vll.jal. 



V-mx. 



V.md. 



X.lar. 



tr.a. 



Fig. 39. — A diagram of a dissection, from the left side, of the forepart 

 of the body of a frog. — Partly after Marshall. 



V.-X. t Cranial nerves; V.md., V.mx., V.op., mandibular, maxillary, and 

 ophthalmic branches of fifth cranial nerve; Vll.Jid., VILpaL, hyoman- 

 dibular and palatine branches of seventh cranial nerve ; IX., branch of 

 ninth cranial nerve to seventh ; IX"., main branch of ninth cranial nerve ; 

 X.c, X.g., X.lar., X.p., cardiac, gastric, laryngeal, and pulmonary branches 

 of tenth cranial nerve ; 1, 2, spinal nerves ; ec, epicoracoid ; Etc., Eustachian 

 tube'; hy., hypoglossal; i.v.c, inferior vena cava; /.aw., left auricle; s.v., 

 sinus venosus ; s.v.c, left superior vena cava ; sy., sympathetic chain ; 

 tr., transverse process of second vertebra; tr.a., truncus arteriosus; v., 

 ventricle; jr., xiphisternum. 



branch, which runs outwards and forks into a hyoidean 

 branch, to the muscles of the hyoid, and a mandibular or 

 chorda tympani to the lower jaw. The eighth, auditory, 

 or acoustic nerve arises from the side of the medulla with 

 the seventh, enters the auditory capsule, and ends in the 



1 This ganglion is formed by the fusion of two ganglia which are 

 distinct in the tadpole. One is the Gasserian ganglion and belongs to 

 the fifth nerve j the other is the geniculate ganglion and belongs to the 

 seventh. 



