THE CORPUS CALLOSUM. 



423 



be ascribed to coincident affections of other parts, make it 

 probable that the office which is commonly assigned to it, of 

 enabling the two sides of the brain to act in concord, is exer- 

 cised only in the highest acts of which the mind is capable. 

 And this view is confirmed by the very late period of its de- 

 velopment, and by its absence in all but the placental Mam- 

 malia. 1 



FIG. 150. 



View of the corpus callosum from above (from Sappey after Foville). ^. The 

 upper surface of the corpus callosum has been fully exposed by separating the cere- 

 bral hemispheres and throwing them to the side ; the gyms fornicatus has been 

 detached, and the transverse fibres of the corpus callosum traced for some distance 

 into the cerebral medullary substance. 1, the upper surface of the corpus callosum ; 

 2, median furrow" or raphe ; 3, longitudinal striae bounding the furrow ; 4, swelling 

 formed by the transverse bands as they pass into the cerebrum ; 5, anterior extrem- 

 ity or knee of the corpus callosum ; 8, posterior extremity ; 7, anterior, and, 8, pos- 

 terior part of the mass of fibres proceeding from the corpus callosum ; 9, margin of 

 the swelling ; 10, anterior part of the convolution of the corpus callosum ; 11, hem or 

 band of union of this convolution; 12, internal convolutions of the parietal lobe; 

 13, upper surface of the cerebellum. 



1 See oases of congenital deficiency of the corpus callosum, by Mr. 

 Paget and Mr. Henry, in the twenty-ninth and thirty-first volumes of 

 the Medico-Chirurgical Transactions. 



