460 



THE RABBIT. PHYLUM CHORDATA 



cavity to the dorsal surface or pallium, where it forms a cortex. 

 It is almost smooth, but there can be seen on it faint indications 

 of some of the furrows or sulci which in man are deep and 

 numerous and divide the surface into convolutions. Midway 

 at the side of each hemisphere is a shallow groove, known as the 

 lateral or Sylvian fissure, which separates a posterolateral 

 temporal lobe from the frontal and parietal lobes. On the under 



Fig. 361. — The brain of a rabbit from below. 



c al.. Corpus albicans ■,fl., flocculus \fr.l., frontal lobe of the cerebral hemisphere ; m.ob., medulla oblongata ; 

 ol.b., olfactory bulb ; ol.i., olfactory tract ; p.V., pons Varolii ; pit., pituitary body ; py.l., pyriform 

 lobe rh.f., rhinal fissure ; Sy.f., Sylvian fissure ; tp.l., temporal lobe of the cerebral hemisphere ; 

 //., ///., V.-XII., roots of the cranial nerves. 



side a longitudinal rhinal fissure marks off the frontal and 

 temporal lobes from a region median to them known as the 

 rhinencephalon, which consists of a pyriform lobe behind and the 

 olfactory lobe in front. The latter consists of the olfactory tract 

 and the olfactory bulb, which projects in front beyond the frontal 

 lobe. 



In each hemisphere the pallium with its cortex extends over 

 the corpus striatum, where the grey matter remains internal. 

 This disposition is due to a great expansion of an area (the 

 neopallium) of the dorsal region of the pallium of lower verte- 

 brates, which has thrust apart the lateral and median regions. 



