258 THE NERVOUS SYSTEM 



is a more prominent ridge with tooth-like secondary elevations. Within this second 

 ridge terminate the fibers of visceral sensation and taste from the seventh, ninth, and 

 tenth nerves. It is known as the visceral lobe or -visceral sensory column. Beneath the 

 groove which separates these two ridges are located the motor nuclei of the fifth, 

 seventh, ninth, and tenth cranial nerves. These nuclei supply visceral musculature 

 and constitute the visceral motor column. The dorsal part of the lateral wall of the fossa 

 forms another prominent ridge, which just caudal to the cerebellum is redundant and 

 folded on itself to form an ear-shaped projection. This auricular fold, sometimes 

 called the lobus linese lateralis, and the prominent margin just caudal to it belong to the 

 acusticolateral area and contain the centers for the reception of impulses coming from 

 the ear (N. VIII) and from the sense organs of the lateral line (Nn. VII and X). Ad- 

 jacent to the acusticolateral area is a portion of the medulla oblongata which is concerned 

 with the reception of sensory impulses from the skin which reach the medulla oblongata 

 along the fifth and tenth nerves. The nuclei of the acusticolateral and general cutane- 

 ous areas together constitute the somatic afferent column. 



14. Locate these functional columns on your specimen. Note the close relation of 

 the olfactory bulb to the nasal sac. By comparison with Fig. 13 locate on your speci- 

 men the olfactory portions of the brain. What part of the brain is especially associated 

 with the eyes? 



15. Cut the nerve roots at some distance from the brain. Remove the brain, 

 being careful not to injure the olfactory bulbs. Now study the lateral and ventral 

 surfaces of the brain in order to locate more accurately the points of origin of the various 

 cranial nerves (Fig. 10). 



16. Now study the parts of the brain which belong to the rhombencephalon. Which 

 parts are they, and what is their relationship to each other? (Figs. 8, 10 and p. 26.) 



17. Study the parts of the brain which belong to the mesencephalon. Which 

 are they, and what relationship do they bear to each other? (Figs. 8, 10 and 

 p. 28.) 



18. In the same way study the parts belonging to the diencephalon (Figs. 8, 10 

 and pp. 28, 29). Make a list of these parts. Tear away the membranous roof of the 

 third ventricle and examine that cavity. 



19. Note the external form of the telencephalon and the parts which compose it 

 (Figs. 8, 10). Students working at adjacent* tables should cooperate in the work 

 which follows in order that two sharks' brains may be available. With a sharp razor 

 blade divide one in the medial sagittal plane; and with a sharp scalpel open up the 

 ventricles in the other as indicated in Fig. 9. Study the ventricles of the brain as they 

 are displayed in these preparations and in Figs. 9 and 11. 



20. Find the velum transversum and the ridge produced by the optic chiasma. 

 All that part of the brain which lies rostral to these structures belongs to the telen- 

 cephalon. Study the telencephalon in detail (Figs. 8-11 and p. 30). Of what parts 

 is it composed, and what are their relations, to each other? Pay special attention to 

 the several parts of the telencephalic cavity. 



THE BRAIN OF THE FETAL PIG 



21. Using a pig embryo of about 35 mm., slice off the skin and a small amount of 

 the underlying tissue on either side of the head with a sharp razor. Then at one careful 



