1733. From these things it may be evident how difficult it is to perceive the quality of those who are in the interior, and, still more, who are in the inmost heaven, as they constitute the membranules or meninges over the minute organs of the brain, and round about its more tender fibers, which, as they do not appear to the eye, are not perceived by man; while yet if we understood the nature of these meninges, we should be able to apprehend somewhat in regard to those spirits who sustain a similar relation to the interior and inmost heaven. As these minute organs with their coverings and interior contents are invisible to us, how much more those spirits who constitute, and, as it were, contain substantial realities.