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ZOOLOGY 



SfccT- 



roofed over by the corpus callosum, a narrow anterior prolongation, 

 or anterior cornu, a posterior cornu, which runs backwards and 

 inwards, and a descending cornu, which passes at first almost directly 

 outwards, then downwards, and finally inwards and forwards. On 

 the floor of the body of the ventricle, and continued along the whole 

 extent of the descending cornu, is a prominent ridge of nearly 

 semicircular transverse section the hippocampus (hp. m.) ; this 

 corresponds in position with a groove, the hippocampal sulcus, on the 



cp.cl. 



9f.l 



c.rs 



c.rv. 



p.pn. 

 r.rn. 



FIG. 1106. Lepus cuniculus. Two dissections of the brain from above*(nat. size). In A 

 the left parencephalon is dissected down to the level of the corpus callosum : on the right 

 the lateral ventricle is exposed. In B the cerebral hemispheres are dissected to a little 

 below the level of the genu of the corpus callosum ; only the frontal lobe of the left 

 hemisphere is retained ; of the right a portion of the temporal lobe also is left ; the velum inter - 

 positum and pineal body are removed, as well as the greater part of the body of the fornix, 

 and the whole of the left posterior pillar ; the cerebellum is removed with the exception 

 of a part of its right lateral lobe. a.co. anterior commissure ; a.fo. anterior pillar of fornix ; 

 a.pn. anterior peduncles of cerebellum ; b.fo. body of fornix ; cb l . superior vermis of cere- 

 bellum ; cb". its lateral lobe ; c.gn. corpus geniculatum ; c. h. cerebral hemisphere ; ch. pi. 

 choroid plexus ; cp. cl. corpus callosum ; cp. s. corpus striatum ; c.rs. corpus restiforme ; 

 d.p. dorsal pyramid ; fl. flocculus ; hp. m. hippocampus ; m.co. middle commissure ; o./ 1 . 

 anterior, and o.l~. posterior lobes of corpora quadrigemina ; olf. olfactory bulb ; o. th. optic 

 thalamus ; o.tr. optic tract ; p.co. posterior commissure ; p.fo. posterior pillar of fornix 

 (taenia hippocampi) ; pn. pineal body ; pd.pn. peduncle of pineal body ; p.pn. posterior 

 peduncles of cerebellum ; P.M. fibres of pons Varolii forming middle peduncles of cerebellum ; 

 sp.lu. septum lucidum ; st. 1. stria longitudinalis ; t. s. tocnia semicircularis (narrow band of 

 white matter between corpus striatum and optic thalamus) ; v.vn. valve of Vieussens ; 

 v 3 , third ventricle ; v 4 , fourth ventricle. (From Parker's Zootomy.) 



inner surface of the temporal lobe. Internally the two hippocampi 

 merge in a median commissural area the psalterium or lyra (ly.). 



Running along the anterior edge of the hippocampus is a ridge 

 of fibres the tcenia hippocampi oxfimbria which passes down into 

 the descending cornu. The union of the two tsenise forms a median 

 longitudinal strand, the body of the fornix, which, as already 

 explained, lies below the corpus callosum, continuous with the 

 splenium of the latter behind, but diverging from it anteriorly by 



