344 DISSECTION OF THE EABBIT 



Sylvian fissures. In front, they project some 

 distance beyond the hemispheres. 



c. The infundibulum is a median rounded elevation, 



lying between the temporal lobes, about the 

 middle of the length of the brain : at its apex is 

 the rounded vascular pituitary body. This latter 

 is usually left behind in the pituitary fossa in 

 the base of the skull when the brain is removed : 

 in this case there is at the apex of the infundi- 

 bulum a slit-like aperture, leading into the third 

 ventricle. 



d. The optic chiasma is a transverse band of nerve 



fibres, lying immediately in front of the infundi- 

 bulum. From its anterior border the optic nerves 

 arise, and from its outer ends the optic tracts 

 may be followed backwards towards the optic 

 lobes by gently pressing aside the temporal lobes. 



e. The corpus mammillare, or corpus albicans, is a 



small rounded median elevation, immediately 

 behind the infundibulum. 



f. The pons Varolii is a stout band of transverse 



nerve-fibres, which crosses the ventral surface 

 of the medulla, opposite the posterior ends of the 

 hemispheres. It connects the two sides of the 

 cerebellum with each other. 



g. The crura cerebri are two large bands of nerve-fibres, 



immediately in front of the pons Varolii, which 

 run forwards, diverging from each other, and 

 connect the medulla oblongata with the hemi- 

 spheres. 



h. The medulla oblongata, as seen from the ventral 

 surface, is broad in front and gradually narrows 

 behind. It is marked by a median ventral fissure, 

 bordered by two narrow bands, the ventral 

 pyramids. At the outer sides of the pyramids, 

 immediately behind the pons Varolii, are a pair 

 of oblong patches of transverse nerve-fibres, the 

 corpora trapezoidea. 



