The results clearly showed that the corpus callosum connects cells with each other so that their receptive fields and can go to the right, middle and left of the vertical. Thus, it sticks together like the two halves of the world picture. To better imagine that, suppose that the original cortex of the brain is integrally formed, not divided into two hemispheres. In this case, the field of 17 would have the form of a continuous layer on which to display all the visual field. Then neighboring cells to implement such features as, for example, sensitivity to motion and orientation selectivity, would have to have, of course, complicated system interconnections. Now imagine that the "designer" (whether it be God, or, say, natural selection) decided that it can not continue to leave - now half of all cells should form one hemisphere, and the other half - the other hemisphere. What then to do with the whole set of cell-cell contacts if the two sets of cells must now move away from each other? Apparently, you can simply stretch these ties, creating one of the corpus callosum. In order to eliminate the delay in the transmission of signals on this longer path (in humans of about 12-15 centimeters), it is necessary to increase the transfer rate by providing fiber myelin sheath. Of course, in fact, nothing in the process of evolution did not occur; Long before there was bark brain has already had two separate hemispheres.