648 



MAMMALIA. 



side of the thalamencephalon, there is a rounded swelling, called the 

 corpus geniculatum. The roof of the third ventricle is formed by a 

 thin membrane or velum, with a plexus of blood vessels. In the 

 anterior wall of the third ventricle lies the small anterior commissure ; 

 across the third ventricle the large middle commissure runs ; in the roof 

 of the hind part of the ventricle lies a small posterior commissure. 

 The optic lobes are fourfold — corpora quadrigemina. They are in 



Fig. 282. — Dorsal view of rab- 

 bit's brain, with most of 

 cerebellum cut away. — After 

 Krause. 



olf.L, Olfactory lobes; c.h., cere- 

 bral hemispheres; o.L, optic 

 lobes ; 4 v. t fourth ventricle 

 (exposed); j.c, spinal cord; 

 10, root of vagus; C6., lobe of 

 cerebellum. 



Fig. 283, — Under surface of rabbit's 

 brain. — After Krause. 



olf.L 1 Olfactory lobes ; o.t., olfactory tract ; 

 f.L, frontal lobe of cerebral hemisphere ; 

 ck., optic chiasma ; I.e., infundibulum ; 

 cm., corpus mammillare ; 3, root of 

 oculomotor ; 4, root of pathetic ; 5, 

 root of trigeminal ; 6, root of abducens ; 

 7-8, roots of facial and auditory; FL, 

 flocculus of cerebellum; H., 12th or 

 hypoglossal nerve ; 10, roots of vagus ; 

 9, the line runs in front of the root of 

 the glosso-pharyngeal to the root of 6 ; 

 p.v., pons Varolii; t.L, temporal lobe 

 of cerebral hemisphere. 



large part covered by the cerebrum. Between them runs the iter con- 

 necting the third ventricle and the fourth. The floor of this passage is 

 formed by the thick crura cerebri which connect the medulla with the 

 cerebrum. 



The cerebellum is divided into a median and two lateral lobes, and is 

 marked by numerous folds, mostly transverse. The two sides are con- 

 nected ventrally by the pons Varolii, lying across the anterior ventral 

 surface of the medulla. 



