Wonders of the World, Ordeals of the Soul, Revelations of the Spirit. Lecture 9 of 10.Rudolf Steiner, Munich, August 26, 1911:
Yesterday I had to point out how a kind of reversal of the forces which led to a densification of the body is taking place in the human organization. As an example of this I drew attention to a kind of etherization of the coarser physical substance of the blood which emanates all the time from our system of heart-and-blood circulation, with the result that the finest elements of the blood are passing over all the time into the same substance as that of which the human ether body consists. And we have seen that these etheric elements stream upward from the heart in quite distinct currents and permeate the brain; we have seen further that it is in fact because this newly formed element of our etheric body streams through the brain that we are able to develop knowledge which goes beyond the completely egotistic knowledge of what takes place within our own organization. I tried to make it clear that unless these etheric streams were to rise up from the heart to the brain, only ideas, concepts, feelings connected with our own bodily organization could find expression through the instrument of the brain.