1734. Those who constitute the meninx over the brain are genii, for that meninx is full of blood; in like manner those who constitute the meninx over the smaller organs of the brain. But those who invest the fascicles of the fibers and the interior nerves are spirits; for as the fibers spring from their organic principles, so also spiritual things from celestial. Moreover, as in the fetus every membrane is charged with blood, and its derivative fibers are, as it were, not bloody, so also it is with these genii, and so on. - 1748, March 27.