542 



THE CEREBRUM. 



layer, and beneath them is cineritious matter continuous with that of 

 the surface of the hemisphere. Along the inner edge of this eminence is 

 seen a narrow white band, named corpus fimbriafum or tccnia hippocamjyi 

 (fig, 381, 6), which is prolonged from the fornix ; to the inner side of 

 the tR3nia is a part of the choroid plexus, and next to that the back of 



Fig. 381. Fig. 381, A. — Lower a>'d Back Part of thk 



Cerebrum op the Left Side, showing the 

 Posterior and Descending Cornua of the 

 Lateral Ventricle opened (altered from 

 Hirschfeld and Leveille). J 



1, Apex of temporo-splienoidal lobe ; 1', un- 

 cinate convolutioQ ; 2, cut surface of the cere- 

 bral hemisphere ; 3, point of the posterior 

 cornu of the lateral venti-icle ; 3', eminentia 

 collateralis ; 4, cut surface of the lower and 

 back part of the corpus callosum divided near 

 the middle ; 4', placed on the extension of the 

 corpus callosum into the cerebral hemisphere, 

 points by a line to the hippocampus minor in 

 the posterior cornu ; 5, cut edge of the posterior 

 pillar of the fornix passing down at 5', into 

 the hippocampus major and corpus fimbriatum ; 

 6, placed on the hippocampus major points to 

 the continuation of the corpus fimbriatum or 

 tiX'uia hippocampi ; 6', lower part of hippo- 

 campus major ; 7, fascia dentata on the inside 

 of the white substance of the taenia. 



Fig. 381, B. — Section of the Right Hippo- 

 campus Major to show the arrangement 

 OF the Grest and White Substance (from 

 Mayo). 



a, white layer on the surface of the hippo- 

 campus ; h, grey substance which is involuted 

 from the surface of the neighbouring convolution ; 

 c, fascia dentata ; d, uncinate convolution ; be- 

 tween c and d dentate fissure ; c, (placed on 

 the eminentia collateralis) cavity of the lateral 

 ventricle. 



the optic thalamus. This cornu differs 

 from the others in respect that it is 

 not a mere cul-de-sac, but, by the 

 separation of the membranes, can be made to communicate in its whole 

 length with the surface of the brain by the fissure through which the 

 choroid plexus enters. 



The posterior cornu projects backwards into the substance of the 

 posterior lobe. At its extremity it is pointed, and directed inwards. 

 On its inner side is a curved and pointed longitudinal eminence, 

 named hippocampus minor, ergot, or calcar avis ; and at the junction of 

 the posterior with the descending cornu, between the hippocampus 

 major and minor, is a smooth eminence, named eminentia collateralis, 

 or 2yes accessorius, which may extend some way down the descending 

 cornu behind the great hippocampus. 



The hippocampus minor is only the convex side of the fold of 

 cortical substance which forms the calcarine sulcus, and in like manner 

 the eminentia collateralis corresponds with the posterior branch of the 

 fissure of Sylvius. 



