66. But this may be illustrated in the first place by comparisons drawn from the three kingdoms of nature: animal, vegetable, and mineral. From the animal kingdom: When the food becomes chyle, the blood vessels extract and call forth from it their blood, the nervous fibers their fluid, and the substances that are the origins of the fibers their animal spirit. From the vegetable kingdom: The tree, with its trunk, branches, leaves, and fruit, stands upon its root, and by means of its root it extracts and calls forth from the ground a grosser sap for the trunk, branches, and leaves, a purer for the pulp of the fruit, and the purest for the seeds within the fruit. From the mineral kingdom: In some places in the bowels of the earth there are minerals impregnated with gold, silver, and iron, and each of these metals draws its own element from the exhalations stored up in the earth.