THE NERVOUS SYSTEM. 



305 



1, Anterior extremity. 



2, Posterior extremity, of the great 



central fissure of the cerebrum. 



3, 3, 3. Its anterior lobes. 



4, 4. Its middle lobes. 



5, 5. Fissure of Silvius, separating the 



anterior from the middle. 



6, 6. Posterior lobes. 



7, 7. Convolutions of the external 



surface of the hemispheres. 



8, Infundibulum. 



9, Tuber cinereum. 



10. Corpora pisiformia. 



11. Grey substance between them ; and , 



12. The anterior prolongations of the 



mesocephalon, or crura cerebri. 



1 3- Inferior surface of the mesocepha- 

 lon, and the groove which lodges 

 the basilar artery. 



14. Groove separating the mesoce- 

 phalon and the superior extre- 

 mity of the chorda oblongata. 



15,15. Posterior prolongations of the 

 mesocephalon, or crura cerebelli. 



16, 16. Inferior surface of the lobes of 



the cerebellum. 



17. Anterior, and 



18, 18. Posterior, parts of the circum- 



ference of the cerebellum. 



19. Fissure separating the lobes of the 



cerebellum behind. 



20. Superior extremity of the spinal 



chord. 



21. Central groove, which divides 



22. The corpora pyramidalia. 



23. Corpora olivaria. 



24. Corpora restiformia. 



25. Olfactory nerve, 



26. Its bulb, 



27. Extent, 



28. Its middle, and 



29. Internal, root. 



30. Optic nerves after their decussa- 



tion. 



31. Their decussation. 



32. Optic nerves before their decus- 



sation. 



33. Common motor nerve of the eye. 



34. Internal motor, or pathetic, nerve, 



35. Trigeminus or tri facial. 



36. External motor nerve of the eye. 



37. Facial nerve. 



38. Acoustic nerve. 



39. Glosso-pharyngeal or gustatory. 



40. Pneumono-gastric or vagus. 



4 1 . Accessory. 



42. 42. Fibres of reinforcement of the 



accessory. 



43. Roots of the hypoglossal, plunged 



in the groove between the para- 

 tnidal and olivary bodies. ( Gall.) 



and placed below the posterior part of the cerebrum ; a third, 

 which unites these, is much smaller than the second, and called 

 mesocephalon or tuber annulare or pons Varolii ; and an apparent 

 prolongation of this, still smaller, and termed chorda oblongata 

 or medulla oblongata; an apparent prolongation of which, again, 

 is the chorda, or medulla, spinalis. 



The cerebrum is divided down to its middle into two equal 

 portions, termed hemispheres. Each of these, again, consists of 

 three portions or lobes ; an anterior, a middle, and a posterior. 

 The outermost part of the cerebrum is rendered far more exten- 

 sive than the dimensions of the organ, by these divisions ; and 

 still more by being furrowed to about an inch in depth, the 

 two sides of each furrow being in contact, so that what are 

 termed convolutions exist. The inner surface of the small intes- 

 tines is greatly increased by projections of the mucous membrane ; 

 the inner surface of the lungs, and of glands, by being divided 

 into innumerable tubes and cells : whence there is far more ab- 

 sorption of chyle, far more changes of the blood and air, and far 



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