482 THE BRAIN 



its fellow of the opposite side by a faint median furrow. 

 The stria longitudinalis lateralis is placed more laterally. 

 So thin is the grey coating of the corpus callosum that 

 the transverse direction of the bundles of callosal fibres 

 can be easily seen through it. 



The striae with the thin layer of grey matter associated with them 

 represent a gyrus called the gyrus supracallosus. 



The two extremities of the corpus callosum (Fig. 192) are 



Genu of 



Olfactory tract 



Lamina tenuinalts 



Optic chiasma , , 



thrown back ^^L<^^JI^^^P? (jr y rus subcallosus 



FIG. 193. Anterior end of the Corpus Callosum and the Subcallosal Gyri 

 as seen from below when the frontal lobes of the hemispheres are 

 slightly separated from each other. (From Cruveilhier. ) 



greatly thickened, whilst the intermediate part, the truncus 

 (O.T. body} is considerably thinner. The massive posterior 

 end, which is full and rounded, lies over the mesencephalon, 

 and extends posteriorly as far as the highest point of the cere- 

 bellum. It is called the splenium. The anterior end, which 

 is not quite so massive, is folded, downwards and posteriorly, 

 upon itself, and is called the genu. The recurved lower 

 portion of the corpus callosum rapidly thins as it passes 

 posteriorly, and is termed the rostrum. The fine terminal 

 edge of the rostrum, the lamina roslralis, is connected with 

 the lamina terminalis (Fig. 192). 



Both the lateral and the medial longitudinal stria3, which 

 lie upon the upper surface of the corpus callosum, turn 



