BASE OF THE BRAIN. 



287 



in a sulcus which separates the marginal from the in 

 ternal orbital convolution. 



4. Fissure of Sylvius. Entirely separates the frontal 

 from the temporo-sphenoidal lobe. It begins external 

 to the anterior perforated space. 



13 



FIG. 125. BASE OF BRAIN. 



1, olfactory bulb; 2, optic nerves; 3, anterior perforated space: 4. tractus optictis; 6, 

 cms cerebri : 6, third pair of nerves: 7. fourth pair of nerves: 8. fifth pair of nerves: 9, 

 sixth pair of nerves: 10, pyramid: 11. olivary body; 12. vertebral artery; 13, anterior 

 spinal artery ; 14, anterior cerebral artery ; 15, lamina cinerea ; 16. fissure of Sylvius, which 

 lodges the middle cerebral artery ; 17. tuber cinereum ; 18. corpora albicantia ; 19, posterior 

 perforated space; 20, posterior cerebral artery; 21, superior cerebellar artery: 22, pens 

 Varolii ; 23, anterior cerebellar artery : 24. seventh and eighth pairs of nerves ; 25, ninth, 

 tenth, and eleventh pairs of nerves ; '26, twelfth pair of nerves : 27, cerebellum. 



5. Anterior Perforated Space. Continuous with the 

 lamina cinerea and tuber cinereum is a triangular layer 

 of gray matter, at the inner part of the fissure of Sylvius. 



