CORPUS CALLOSUM. 529 | 
is highly arched from before backwards, and presents a convex upper surface and a 
concave lower surface. 
The upper surface of the corpus callosum forms the bottom of the great longi- 
tudinal fissure, and on each side of this it is covered by the callosal gyrus. Only 
in its posterior part is it touched by the falx cerebri; in front, this process of dura 
mater falls considerably short of it. The upper surface of the callosum is covered 
by a thin layer of gray matter continuous at the bottom of the callosal sulcus with 
the gray cortex on the surface of the hemisphere. In this there are embedded on 
either side of the mesial plane two delicate longitudinal bands of fibres, called 
respectively the stria longitudinalis medialis and lateralis. The stria longitudinalis 
medialis is the more strongly marked of the two, and it is separated from its neigh- 
bour of the opposite side by a faint mesial furrow. The stria longitudinalis lateralis 
Genu 
Cingulum Frontal fibres 
Cut surface 
Fibres of corona radiata~— Transverse fibres 
_7 of corpus 
; callosum 
Intersection of 
callosal and corona 
radiata systems of 
fibres 
Corpus callosum 
T > Tapetum 
__ Inferior longi- 
tudinal bundle 
—Forceps major 
Tapetum 
Splenium 
Fie. 392.—THE Corpus CaLLosum, exposed from above and the right half dissected, 
to show the course taken by its fibres. 
is placed further out, under cover of the callosal gyrus. The thin coating of gray 
matter, with the two striae, represent an aborted convolution, termed the gyrus 
supracallosus. So thin is the gray coating supplied by this gyrus that the trans- 
verse direction pursued by the callosal fibres proper can be easily perceived 
through it. 
The two extremities of the corpus callosum are much thickened, whilst the 
intermediate part or body is considerably thinner. The massive posterior end, 
which is full and rounded, lies over the mesencephalon and extends backwards as 
far as the highest point of the cerebellum. It is called the splenium, and it consists 
of an upper and a lower part. The latter is bent forwards under the upper part, to 
the inferior surface of which it is closely applied. The anterior end of the corpus 
callosum is not quite so massive and is folded downwards and backwards on itself. 
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