1691. When I asked who they were, they did not want to speak. It was told that they do not speak willingly, and on being compelled to speak, they did not like to, saying that then their character would be exposed. I realized that they were those who constitute the province of the dura mater, the general covering, or, rather, supporting layer for those substances in the brain that are spiritual and heavenly. For even though the dura mater is stretched over and therefore appears above [the brain], nevertheless it does not overlie, but underlies those substances, occupying the outward parts of the brains, while spiritual and heavenly substances occupy their inward parts.