THE CEREBRUM 



481 



of the cerebrum. It is placed nearer the anterior than the 

 posterior end of the brain, and it unites the medial surfaces of 

 the two cerebral hemispheres throughout very nearly a half of 

 their antero-posterior length. 



Its upper surface is convex antero-posteriorly and concave 

 from side to side, and it forms the bottom of the longitudinal 

 fissure. On each side of the fissure it is covered by the 

 gyrus cinguli (O.T. callosal gyrus). Only in its posterior part 



ii 10 9 8 7 



FIG. 192.- Median section through the Brain. 



1. Fornix. 6. Corpora quadrigemina. 



2. Tela chorioidea. 7. Ant. medullary velum. 



3. Pineal body. 8. Aquaeductus cerebri. 



4. Vena magna cerebri. I 9. Oculo-motor nerve. 



5. Splenium of corpus cal- 10. Corpus mamillare. 



losum. 



ii. hifundibulum. 



12. Optic chiasma. 



13. Lamina terminalis. 



14. Anterior commissure. 



15. Foramen interventriculare. 



16. Genu of corpus callosum. 



17. Septum pellucidum. 



is it touched by the falx cerebri ; anteriorly, that fold of dura 

 mater falls considerably short of it. The upper surface of 

 the corpus callosum is coated by an exceedingly thin layer 

 of grey matter continuous, at the bottom of the callosal 

 sulcus, with the grey cortex of the hemisphere. In this are 

 embedded, on either side of the median plane, two delicate 

 longitudinal bands of fibres called the striae longitudinales 

 medialis and lateralis. The stria longitudinalis medialis is the 

 more strongly marked of the two, and it is separated from 

 VOL. ii 31 



