THE MYELON. 



06 



Fig 23. — A diagrammatic view of the Chief Trunks of the Cerebro-spinal and Sympathetic 

 Nervous Systems of Rana esculeriia seen from below Ct^A'ice the size of nature). — I. The 

 olfactory nerves. N. The olfactory sac. II. The optic nerve. 0. The eye. Z. op. 

 The optic lobes. Ta. Optic tracts passing from the optic lobes to the chiasma. behind 

 which lies the pituitary body. III. Ociilomotovius. IV. Patheticus. Y The tri- 

 g'eminal, with which the abducens (Yl.), facialis (VII.). and the upper end of the sym- 

 pathetic (Fas'.), are closely connected. Branches of this nervous plexus are V.a. the 

 nasal and ophthalmic branches of the fifth and the alxJiicens. V, b, c, d. the palatine, 

 maxillary, and mandibular branches of the fifth. V, e, the tympanic branch into which 

 the proper facial nerve (VII.) enters, and, with a branch of the vagus, forms the so- 

 caUed facial nerve of the Frog. F. VIII. The auditory nerve. X, ^vith its branches 

 Jfi, X^, A'3, X*, represents the glossophaiyngeal and the vagus. The medulla (il> 

 longata {Myelence]>halon) ends, and the medulla spinalis {Myelon) begins, about tlie 

 region marked by the letter J/. J/ 1-10, the spinal nerves. 3/2, the brachial nerves, 

 31 7, 8, 9, the ischiatic plexus, from which proceed the crural (N. c.) and ischiatic (N. i.) 

 nerves. S. The trimk of the sympathetic. S.M. The commimicating branches Avitb 

 Uie spinal ganglia. S 1-10. The"symp;it±ieti£ canclia. 



