The same principle holds good for man and beast. They also need 'young material' for their nourishment, so that the type active in them - which in animals is the group-soul of the species and in man is the single individual - can express its true form and character. (We saw earlier that the will requires 'young' material in order to penetrate into the material layers of the muscles, as happens when the limbs are set in motion). In this respect, the difference between ensouled creatures and plants is that, what is harmful to plants is natural for men and animals: when taking nourishment the latter are able to bring about quickly and purposefully a transformation of matter into the purely dynamic state. Their metabolic system is designed to enable them to take alien material from outer nature and to transform it through the forces of the various digestive enzymes; in the course of this process the material passes through a condition of complete 'chaos'.