30 LABORATORY OUTLINE OF NEUROLOGY 



to an understanding of the following sections), see Herrick, '18, 

 Chap. IX, and Johnston ('06), Chap. V. 



16. The nerve components of the dogfish have been carefully 

 studied microscopically by Dr. H. W. Norris and Miss S. P. 

 Hughes, who have very kindly prepared for us the accompany- 

 ing drawings Figs. 4 and 5) from a detailed account to be 

 published shortly ('19). The systems of nerve components 

 mentioned 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 and muscle sense); VII 

 (lateral line fibers) ; VIII (acoustic and vestibular) ; IX (lateral 

 line fibers); X (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. 5 A)]. 



(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 

 visceral 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 canial 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 cerebral hemisphere (Figs. 2 and 5 A). 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. 



