THE CEEEBEAL COMMISSUEES AND SEPTUM PELLUCIDUM. 631 



tissue with the lamina terminalis on the antero-superior aspect of the anterior 

 commissure (Fig. 558). , 



The inferior surface of the corpus callosum, on each side of the median plane, is 

 coated with ependyma (Fig. 564, p. 635), and forms the roof of the anterior horn 

 and the central part of the lateral ventricle. In the median plane, however, it is 

 attached to subjacent parts, viz., to the septum pellucidum in front and directly 

 or indirectly (Fig. 564) to the body of the fornix behind (Fig. 558, p. 630). 



The transverse fibres of the corpus callosum, as they enter the white medullary 

 centre of the cerebral hemisphere, separate from each other so as to reach most parts 

 of the cerebral cortex. These diverging fibres are termed the radiatio corporis 



Genu 



Cingulum 



Frontal fibres 



Cut surface 



Fibres of corona radiata 



Intersection of i 

 callosal and corona I 

 radiata systems of i 

 fibres 



Corpus callosum 



Cingulum (cut) 



Transverse fibres 

 of corpus 

 callosum 



Tapetuni 



Inferior longi- 

 'tudinal bundle 



Occipital part of 

 radiation of 

 corpus callosum 



Tapetum 





Stria longitudinalis medialis 



Splenium 



FIG. 559. THE CORPUS CALLOSUM, exposed from above and the right half dissected, 

 to show the course taken by its fibres. 



The lateral longitudinal stria (which lies near the cingulum) is not shown. 



callosi, and they intersect those which form the corona radiata or, in other 

 words, the fibres which extend between the internal capsule and the cerebral 

 cortex (Figs. 570, p. 640, and 576, p. 649). The more anterior of the fibres which 

 compose the genu of the corpus callosum sweep forwards in a series of curves into 

 the anterior frontal region of the hemisphere. A large part of the splenium, 

 forming a solid bundle termed the occipital part of the radiation of the corpus 

 callosum (O.T. forceps major), bends suddenly and abruptly backwards into the 

 occipital lobe (Fig. 559). Fibres from the body and superior part of the splenium, 

 curving round the lateral ventricle, form a very definite stratum, called the 

 tapetum. This is a thin layer in the medullary centre of the hemisphere, which 

 constitutes the immediate roof and lateral wall of the posterior horn arid the 

 lateral wall of the posterior part of the inferior horn of the lateral ventricle 



