480 



THE BRAIN 



long association bundle composed of several systems of fibres 

 which run only for short distances within it. It is closely 

 associated with the gyrus fornicatus. 



Dissection. The gyri and sulci on the medial surface of the left hemi- 

 sphere may now be studied, and then the dissection, which has been 

 carried out with the view of exposing the corpus callosum, may be repeated 



Cingulum 



Fibres of corona radiata 



Intersection of ( 



callosal and corona I 



radiata systems of 1 



fibres I 



Frontal fibres 

 , Genu 



.. Cut surface 



Corpus callosum 



Transverse fibres 

 of corpus 

 callosum 



Inferior longitu- 

 dinal fasciculus 



, Tapetum 



Cingulum 



Splenium \ Forceps major 



Stria longitudinalis medialis 



FIG. 191. The Corpus Callosum exposed from above and the right half 

 dissected to show the course taken by the fibres. 



on the left side. In doing this, however, take care not to injure the medial 

 surface of the left hemisphere posterior to the parieto- occipital fissure. 

 Indeed, an effort should be made to preserve that fissure intact, so that it 

 and the cuneus may be studied afterwards, on this side, in connection with 

 the gyri and sulci on the under surface of the hemisphere. 



The upper surface of the corpus callosum is now exposed, and it will 

 be seen that it unites into one mass the medullary centres of the two 

 hemispheres. The continuous white field, consisting of the corpus callosum 

 and the medullary centre of each hemisphere, receives the name of 

 centrum ovale. 



Corpus Callosum. This is the great transverse commissure 



