9e 



LECTtfRE IV. 



termed the crura cerebri. All the white parts^ with their con- 

 tinuations^ in front and above, and concealed in the cerebral 

 naass, may be termed the iwiinitive brain, inasmuch as this is the 

 original portion which is first of all deposited during the de- 

 velopment of the brain in the embryo. The great mass of the 

 brain consists, as shown by comparative anatomy, of arched 

 parts which gradually grow from the primitive brain and unite 

 in the median line, so that in the interior of the brain there re- 

 mains still a system of cavities, the size of which diminishes in 

 proportion to the development of the cerebi'al mass. 



Fiff. 29. Base of the Human Brain. 



Base of tlie Brain. 1. Anterior lobe. 2. Middle lobe. 3. Posterior lobe 

 of the cerebral hemisphere. 4. Hemispheres of the cerebellum. 5. Vermi- 

 form process of cerebellum. 6. Flocculus. 7. Longitudinal fissure. 8. Ol- 

 factory nerves (first pair). 9. Exit of the olfactory nerve from the brain. 

 10. Crossing of the optic nerves. Chiasma nervorum opticorum (second pair). 

 H. Tuber cinereura. 12. Corpora mammillaria. 13. Oculomotor (third 

 pair). 14. Pons Varolii. 15. Crura cerebeUi. 16. Trigeminal nerve (fifth 

 pair) : immediately before it, the fourth pair : N. patheticus, or tro- 

 chlearis. 17. Abducens (sixth pair) . 18. Facial and auditory nerve : N. faci- 

 alis and N. acousticus (seventh and eighth pair). 19. Pyramidal bodies of 

 the medulla ; at their sides, outwardly, the olivary bodies. 20. Glosso-pha- 

 ryngeal nerve, vagus and accessory nerves (ninth, tenth, and eleventh pair). 

 21. N. hypoglossus (twelfth pair). 22. First cervical nerve. 



