On the Origin of the Fibers in the Pyramid of the Primate Brain. ∗

Abstract

Conclusion

Practically all the heavily myelinated fibers in the pyramids of the monkey's brain arise from the region of the cerebral cortex in which the gigantopyramidal cells of Betz are found. Since we know that all of these fibers cannot be accounted for as arising from such cells they must also come from smaller elements. The fact that Weigert material fails to show any fibers in the pyramids after ablation of the precentral gyri, does not prove that the pyramids are devoid of fibers for smaller elements can plainly be seen with silver stain. Since no fibers remain after removal of all of the cortex none of these smaller fibers can be attributed to an infrapallial origin.