BASE OP THE BRAIN. 425 



The Ports Varolii* (protuberantia annularis, nodus encephali), is 

 the broad transverse band of white fibres which arches like a bridge 



Fig, 141. f 



* Constant Varolius, Professor of Anatomy in Bologna: died in 15/8. He 

 dissected the brain in the course of its fibres, beginning from the medulla ob- 

 longata ; a plan which has since been perfected by Vieussens, and by Gall and 

 Spurzheim. The work containing his mode of dissection, " De Resolutione 

 Corporis Humani," was published after his death, in 1591. 



t The under surface or base of the brain. 1 . The anterior lobe of one hemi- 

 sphere of the cerebrum. 2. The middle lobe. 3. The posterior lobe almost 

 concealed by (4) the hemisphere of the cerebellum. 5. The pyramidal lobe of 

 the inferior vermiform process of the cerebellum. 6. The pneumogastric lobule. 

 7. The longitudinal fissure. 8. The olfactory nerves, with their bulbous ex- 

 pansions. 9. The substantia perforata at the inner termination of the fissure 

 of Sylvius ; the three roots of the olfactory nerve are seen upon the substantia 

 perforata. The commencement of the transverse fissure on each side is con- 

 cealed by the inner border of the middle lobe. 10. The commissure of the 

 optic nerves ; the numeral is placed between the optic nerves as they diverge 

 from the commissure, and rests upon the lamina cinerea of the corpus callosum. 

 11. The tuber ciiiereum, from which the infundibulum is seen projecting. 12. 

 The corpora albicantia. 13. The locus perforatus, bounded on each side by the 

 crura cerebri, and by the third nerve. 14. The pons Varolii. 15. The crus 

 cerebelli of one side. 16. The fifth nerve emerging from the anterior border of 

 the crus cerebelli ; the small nerve by its side is the fourth. 17. The sixth pair 



