379. It is known that there is vital heat in man and in every animal; but its origin is not known. Everyone speaks of it from conjecture, consequently those who have known nothing of the correspondence of natural things with spiritual have ascribed its origin to the heat of the sun, some to activity of the parts and some to life itself; but as they did not know what life was, they simply stopped using that word. But he who knows that there is a correspondence of love and its affections with the heart and its derivations, may know that love is the origin of vital heat. For love goes forth, from the spiritual Sun where the Lord is, as heat, and moreover, is felt by the angels as heat. This spiritual heat, which in its essence is love, is what flows in by correspondence into the heart and its blood, infuses it with heat, and at the same time gives it life. That a man grows hot and, as it were, burns, according to his love and the degree of it, and becomes numb and chilled as it decreases, is known, for it is felt and seen; it is felt from the heat of the whole body, and it is seen from the flush of the face; and extinction of love, on the other hand, is felt from the coldness of the body, and seen from the pallor of the face. Because love is the life of man, the heart is the first and the last of his life. And because love is the life of man and the soul impels its life into the body through the blood, in the Word blood is called the soul (Gen. ix 4; Levit. XVII 14). The various meanings of the word "soul" will be explained in what follows.