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AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



IV. The pathetic nerves are the only, cranial ones which have a 

 dorsal origin. They arise nearly in the middle line just behind 

 the optic lobes and supply the superior oblique muscles. 



All the remaining nerves take origin from the bulb. 



Fig. 47. DOGFISH. A, Diagram of cranio-spinal nerves (slightly altered 

 after Wiedersheim). M, Mouth; Or, margin of orbit (indicated by 

 dotted line); Au, auditory capsule ; Sp, spiracle; ttttt, gill-slits; 

 II., optic ; III, oculomotor; IV., pathetic ; V, ophthalmic branch of 

 trigeminal ; *, its course in front of orbit to join VIP ; V 6 and V c , 

 maxillary and mandibular branches of trigeminal ; VI., abducent ; 

 VIP, ophthalmic branch of facial ; VII., main trunk of facial, where 

 palatine branch runs forward and hyomandibular backward behind 

 spiracle, giving off prespiracular branches ; IX. , glossopharyngeal, 

 forking over first gill-slit; X., vagus, giving off branchial branches 

 which fork over gill-slits, a lateral line branch (Lat), and then supply- 

 ing viscera ; 1-14, first fourteen spinal nerves, forming brachial plexus 

 (Br.pl], from which pectoral fin is supplied. B, Dorsal view of brain. 

 C, Ventral view of brain. ol, Olfactory lobes; pr, prosencephalon ; 

 th, thalamencephalon ; pin, pineal body; py, pituitary body; Li, 

 lobi inferiores ; o.l, optic lobes; e&, cerebellum ; r.b, restiform body; 

 b, bulb ; sp, spinal cord ; II. -X., cranial nerves. 



