THE MYELON. 



65 



Tig 23.— a diagrammatic view of the Chief Trunks of the Cei-obro-spinal and SyinrathPtfo 

 Nervous Systems of Rana esculenia eeen from below (twice the size of nature). — I. Tho 

 olfactory nerves. N. The olfactory sac, II. The optic noi-ve. 0. Tho eye. L. op. 

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

 which lies the pituitary body. 111. OculomntoHvs. IV Patheticus. V The tri- 

 geminal, with which the abdueeiu (\ J.), facialis (VII.). and the upper end of the svm- 

 pathetic (F.9), are closely connected. Branches of this nervous plexus are F.cf/tho 

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

 maxillary, and mandibular branches of the fifth. FJ «, t!io tympanic branch into which 

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

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

 X^, X^, X^^ .r*, represents the glossopharyngeal and the vagus. The medulla ()!•■ 

 longata {Myelencepkalori) ends, and the medulla spinalis (^Jifj/eloii^ begins, about tlie 

 region marked by the letter 3f. 311-10, the spinal nerves. ,1/2, the brachial nerves, 

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

 serves. iS. The trunk of the sympathetic. KAf. The communicating branches viti 

 tho spinal ganglia, tS i-10. The sympathetic; ^anslia. 



