THE EXTRAORGANIC

WO years ago the American Anthropologist published a n article by me' in T which some far-reaching statements were made concerning the relationship of the organic and the cultural. The chief thesis of that paper was that the manufacture and use of tools by the proto-human ancestors of man resulted in the evolutionary improvement of both brain and extraorganic implement in a recipro-causal manner. A closer examination since then of the literature on the evolution and development of the vertebrate nervous system has brought to my knowledge a process which provides a better factual basis for t ha t conclusion than was given in that paper? The phenomenon of neurobiotaxis, with which the name of C. U. Ariens Kappers is closely associated, is a physiological process by which the manufacture and use of extraorganic devices could have affected the primate brain in evolution. Neurobiotaxis is described as follows:a