405. That these three from the will's love follow in order in the understanding can, indeed, be comprehended by the rational man but yet cannot be clearly seen and thus so proved as to command belief. But as love that is of the will acts as one with the heart by correspondence, and wisdom that is of the understanding acts as one with the lungs (as has been shown above) therefore what has been said (in n. 404) about affection for truth, perception of truth, and thought, can nowhere be more clearly seen and proved than in the lungs and the mechanism thereof. These, therefore, shall be briefly described. After birth, the heart discharges the blood from its right ventricle into the lungs; and after passing through these it is emptied into the left ventricle: thus the heart opens the lungs. This it does through the pulmonary arteries and veins. The lungs have bronchial tubes which ramify, and at length end in air-cells, into which the lungs admit the air, and thus respire. Around the bronchial tubes and their ramifications there are also arteries and veins called the bronchial, arising from the vena azygos or vena cava, and from the aorta. These arteries and veins are distinct from the pulmonary arteries and veins. From this it is evident that the blood flows into the lungs by two ways, and flows out from them by two ways. This enables the lungs to respire non-synchronously with the heart. That the alternate movements of the heart and the alternate movements of the lungs do not act as one is well known. Now, inasmuch as there is a correspondence of the heart and lungs with the will and understanding (as shown above), and inasmuch as conjunction by correspondence is of such a nature that as one acts so does the other, it can be seen by the flow of the blood out of the heart into the lungs how the will flows into the understanding, and produces the results mentioned just above (n. 404) respecting affection for and perception of truth, and respecting thought. By correspondence this and many other things relating to the subject, which cannot be explained in a few words, have been disclosed to me. Whereas love or the will corresponds to the heart, and wisdom or the understanding to the lungs, it follows that the blood vessels of the heart in the lungs correspond to affections for truth, and the ramifications of the bronchia of the lungs to perceptions and thoughts from those affections. Whoever will trace out all the tissues of the lungs from these origins, and disclose the analogy with the love of the will and the wisdom of the understanding, will be able to see in a kind of image the things mentioned above (n. 404), and thereby attain to a confirmed belief. But since a few only are familiar with the anatomical details respecting the heart and lungs, and since confirming a thing by what is unfamiliar induces obscurity, I omit further demonstration of the analogy.