DISSECTION OF THE SHARK 29 



tioned at the close of the preceding section are represented in 

 the following cranial nerves of the dogfish: 



(1) Somatic sensory: II (optic); III, IV and VI (fibers of 

 muscle sense); V (general cutaneous); VII (lateral line fibers); 

 VIII (acoustic and vestibular) ; IX (lateral line fibers) ; X (gen- 

 eral cutaneous and lateral line fibers). 



(2) Somatic motor: III, IV and VI (eye-muscle nerves) [in 

 man also XII, for tongue muscles, represented in the dogfish by 

 the hypobranchial nerve (Fig. 5A)]. 



(3) Visceral sensory: I (olfactory); VII, IX and X (general 

 visceral and gustatory nerves). 



(4) Visceral motor: III (ciliary nerves); V (masticatory 

 nerves); VII (nerves of the hyoid musculature [including in 

 man the facial muscles]) ; IX and X (branchial and general vis- 

 ceral motor nerves). 



17. The names of the cranial nerves and their chief branches 

 in the dogfish are given for reference in the following list (cf. 

 Figs. 1 to 5). They should be identified in your specimens, but 

 their names need not be memorized. The human cranial nerves 

 show the same general arrangement, save for the absence in man 

 of all components supplying lateral line organs and for the 

 modification of the IX and X pairs resulting from the loss of the 

 gills. See Section 47. 



I. N. olfactorius. Passes in very numerous short filaments 

 from the nasal sac on the ventral surface of the snout to the very 

 large olfactory bulb. Associated with this nerve is the slender 

 nervus terminalis, running between the nasal sac and the cere- 

 bral hemisphere (Figs. 2 and 5A). It passes along the dorsal 

 surface of the olfactory bulb and the medial surface of the stalk 

 of the bulb to enter the cerebral hemisphere near the median 

 plane. See Locy ('05) and McKibben ('14): 



II. N. opticus. From the eye to the floor of the brain under 

 the thalamus. 



III. N. oculomotorius. From the floor of the midbrain to 

 mm. obliquus inferior and rectus superior, inferior, and medialis. 



IV. N. trochlearis. From the roof of the midbrain to m. 

 obliquus superior. 



VI. N. abducens. From the floor of the medulla oblpngata 

 to m. rectus lateralis. 



