405. The observation that these three elements follow in succession in the intellect from love residing in the will is one that a rational person can indeed comprehend, but still not one that can be clearly seen and thus so confirmed as to be believed. Now because love residing in the will operates by correspondence in union with the heart, and wisdom residing in the intellect in union with the lungs, as we have shown above, therefore what we have just said in no. 404 above regarding an affection for truth, a perception of truth, and thought, can nowhere be more clearly seen and confirmed than in the lungs and their design. Consequently these must be briefly described. [2] The heart after birth transmits blood from its right ventricle into the lungs, and following its passage through them, discharges it [from the left atrium] into its left ventricle, thus opening the lungs.* The heart accomplishes this through the pulmonary arteries and veins. The lungs have bronchial tubes which branch out and finally end in tiny sacs, into which the lungs admit air and so breathe. Surrounding the bronchial tubes and their ramifications are also arteries and veins called the bronchial arteries and veins, arising from the azygos vein or the vena cava and from the aorta. These arteries and veins are separate from the pulmonary arteries and veins. It is apparent from this that blood flows into the lungs by two routes, and flows from them by two routes. That is why the lungs can breathe in a rhythm different from that of the heart. The fact that the alternate motions of the heart and the alternate motions of the lungs do not coincide is something people know. [3] Now because there is a correspondence of the heart and lungs with the will and intellect, as we have shown, and their conjunction by correspondence is such that one functions as the other, it can be seen from the flow of blood from the heart into the lungs how the will flows into the intellect and accomplishes what we have just stated in no. 404 above regarding an affection for and perception of truth, and thought. Their correspondence has disclosed this to me, and many other things as well which cannot be briefly described. [4] Since love or the will corresponds to the heart, and wisdom or the intellect to the lungs, it follows that the heart's blood vessels in the lungs correspond to affections for truth, and that the ramifications of the lungs' bronchial tubes correspond to perceptions and thoughts springing from those affections. Anyone who explores all the tissues of the lungs from their origins and draws a parallel with love in the will and wisdom in the intellect can see, as though in a kind of reflected image, the things described in no. 404 above and be so convinced as to believe them. However, because the particulars belonging to the science of anatomy regarding the heart and lungs are known to few, and to confirm something by means of things unknown induces unintelligibility, therefore I forgo demonstrating the parallelism further. * In the mature heart, blood from the veins enters from the right atrium into the right ventricle, is pumped to the lungs, and returning from there to the left atrium, enters the left ventricle and is pumped through the aorta into the body. In the fetal heart, the venous blood passes from the right atrium through an opening called the foramen ovale into the left atrium and so into the left ventricle, bypassing the right ventricle.