110 



INTRODUCTION TO NEUROLOGY 



brain are indicated; and Fig. 44 shows an enlarged side view 

 of the brain and the sensory roots of the cranial nerves. 



Fig. 42. Dissection of the brain and cranial nerves of the dogfish, 

 Scylliurn catulus. The right eye has been removed. The cut surfaces 

 of the cartilaginous skull and spinal column are dotted, d.l-d.5, Bran- 

 chial (gill) clefts; ep., epiphysis; exl.rect., external rectus muscle of the 

 eyeball; gl.ph., glossopharyngeal nerve; hor.can., horizontal semicircular 

 canal; hy.mnd.VII, hyomandibular branch of the facial nerve; inf. obi., 

 inferior oblique muscle; int.rect., internal rectus muscle; lal.vag., lateral 

 line branch of the vagus nerve; mnd.V, mandibular branch of the trigeminal 

 nerve; mx.V, maxillary branch of trigeminus; olf.cps., olfactory capsule; 

 G//.S., olfactory sac; oph.V.VII, superficial ophthalmic branches of the 

 trigeminal and facial nerves; pfilh., trochlear nerve (patheticus); fil.VII, 

 ])alatine branch of facial nerve; s.obl., superior oblique muscle; .s/>.ro., 

 spinal cord; .s'/nr., spiracle; s.rect., superior rectus muscle; vag., vagus nerve; 

 rr .<;/., vestibule. (After Marshall and Hurst, from Parker and Harwell's 

 Zoology.) 



In fishes there is a system of small sensory canals widely dis- 

 tributed under the skin. These contain sense organs somewhat 

 similar to those in the semicircular canals of the internal ear, and 



