Exploration of the left half of the cerebellum and brain stem from its inferior and medial aspect

Tonsil removed; continuation of its medullary substance into pyramis

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Image #26-4

Exploration of the left half of the cerebellum and brain stem from its inferior and medial aspect

Tonsil removed; continuation of its medullary substance into pyramis

The lateral part of the tonsil has been removed. The biventral lobule is now exposed as it opposed the tonsil across the postpyramidal fissure (secondary fissure). Two major masses of fibers (5, 6) have been cut off as they entered the tonsil from the deep parts of the cerebellum. The more medial of these was previously followed into the uvula. The more lateral group of fibers is continuous medially into folia which join the pyramis.

1. Inferior semilunar lobe (crus II ansiform lobule)
2. Gracile lobule (paramedian lobule)
3. Biventral lobule (dorsal paraflocculus) and postpyramidal fissure (secondary fissure)
4. Branch of posterior inferior cerebellar artery (PICA)
5. Cut ends of fibers which entered lateral part of cerebellar tonsil
6. Cut ends of fibers which entered medial part of cerebellar tonsil
7. Floccular peduncle
8. Secondary flocculus
9. Glossopharyngeal nerve (IX)
10. Inferior olivary nucleus
11. Pyramid (medulla oblongata)
12. Basilar part of pons (midsagittal section)
13. Folium vermis
14. Primary fissure
15. Pyramid (vermis)
16. Cut ends of fibers which entered uvula
17. Brachium conjunctivum (superior cerebellar peduncle)
18. Nodulus
19. Central lobule
20. Cerebellar lingula
21. Pineal body
22. Quadrigeminal plate
23. Occulomotor nerve (III)