NERVOUS SYSTEM 



459 



continuous with the brain, and posteriorly, a Uttle in front of 

 the sacrum, it narrows to a thin filament, the filum terminale, 

 which continues into the tail. It is more or less cylindrical, but 

 somewhat flattened dorsoventrally and has a small median canal. 

 Its appearance in section is described on p. 532. 



THE BRAIN 



, a.ch. p. 

 ' l.v. 



a. c. q. 



ver. ' 



Fig. 360. — The brain of a rabbit, seen from above with part of the right cerebral 



hemisphere cut away. 



a.c q. Anterior corpus quadrigemiiium ; a.ch. p., anterior choroid plexus ; cb., cerebellum ; cer.h., cerebral 

 hemisphere ; ck., cortex ;/?., flocculus ;/>•./., frontal lobe of cerebral hemisphere ; l.v., lateral ventricle ; 

 lat.l., lateral lobe of cerebellum ; m.o., medulla oblongata ; occ.l., occipital lobe of cerebral hemisphere ; 

 ol.b., olfactory bulb ; op.th., optic thalamus ; p.b., pineal body ; p.c.q., posterior corpus quadngenunum ; 

 par.L, parietal lobe of cerebral hemisphere ; f.3, roof of third ventricle ; sp.c, spinal cord ; Sy.f., 

 Sylvian fissure ; tp.L, temporal lobe of cerebral hemisphere ; ver., vermis. 



The brain (Figs. 360-62), which is in origin simply an expansion 

 of the spinal cord, may be divided into fore-, mid-, and hind-brain. 

 The most conspicuous part of the fore-brain is the cerebrum, 

 which consists of two very large cerebral hemispheres divided 

 by a deep cleft or median fissure, at the bottom of which they 

 are joined by a bridge known as the corpus callosum, composed 

 of nerve fibres, nearly all of which run transversely. In the cere- 

 brum the grey matter has migrated from around the central 



