18 



LABOEATOEY OUTLINE OP NEUEOLOGY 



Examine the gills and determine how they work as organs of 

 respiration, noting the direction of flow of water through them 

 and the mechanism by which this flow is maintained. 



spt.r 

 7tt/.mncl.18t 



FIG. 1. Dissection of the brain and cranial nerves of the dogfish, Scyllium 

 catulus. The right eye has been removed. The cut surfaces of the carti- 

 laginous skull and spinal column are dotted. cZ.l-cZ.5, Branchial (gill) clefts; 

 ep., epiphysis; exl.rect., external rectus muscle of the eyeball; gl.ph., glosso- 

 pharyngeal 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; lat.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; oZ/.s., olfactory sac; oph.V.VII, 

 superficial ophthalmic branches of the trigeminal and facial nerves; path., 

 trochlear nerve (patheticus) ; pl.VII, palatine branch of facial nerve; s.obl., 

 superior oblique muscle; sp., spiracle; sp.co., spinal cord; spir., spiracle; 

 s.rect., superior rectus muscle; vag., vagus nerve; vest., vestibule. (After 

 Marshall and Hurst, from Parker and Haswell's Zoology.) 



8. Cut through the skin in the middorsal line and reflect it on 

 the right side as a lateral flap, leaving this flap attached at the 

 lateral border of the head. Locate again the pores of the endo- 



