Also among other veins open and privy, there is a vein, and it is called Artery, which is needful in kind to bear and bring kindly heat from the heart to all the other members. And these arteries are made and composed of two small clothings or skins, called curtels, and they be like in shape, and divers in substance. The inner have wrinkles and folding overthwart, and their substance is hard, and more boystous than the utter be. And without they have wrinkles and folding in length: of whom the substance is hard for needfulness of moving, opening, and closing. For by opening, itself doth receive from the heart and that by the wrinklings and folding in length; by closing, itself doth put out superfluous fumosity, which is done by wrinkling and folding the curtels overthwart and in breadth, in the which the spirit is drawn from the heart. Wherefore they be harder without than all the other veins, and that is needful lest they break lightly and soon. Also these veins spring out of the left hollowness of the heart. And twain of that side are called Pulsative, of which one that is the innermost hath a nesh skin, and this vein is needful to bring great quantity of blood and spirits to the lungs, and to receive in air, and to medley it with blood, to temper the ferventness of the blood. This vein entereth into the lungs and is departed there in many manner wises. The other artery is more than the first, and Aristotle calleth it Horren; this artery cometh up from the heart, and is departed in twain, and the one part cometh upward, and carrieth blood, that is purified and spirit of life to the brain; that so the spirit of feeling may be bred, nourished, kept, and saved. The other part goeth downward, and is departed in many manner wise toward the right side and toward the left. Then mark well, that a vein is the bearer and carrier of blood, keeper and warden of the life of beasts. And containeth in itself the four bloody humours clean and pure, which are ordained for feeding of all the parts of the body. Moreover, a vein is hollow to receive blood the more easily, and as it needeth in kind, that one vein bring and give blood to another vein. Also a vein is messager of health and of sickness. For by the pulse of the arteries and disposition of the veins, physicians deem of the feebleness and strength of the heart. Also if a vein be corrupt, and containeth corrupt blood, it corrupteth and infecteth all the body, as it fareth in lepers, whose blood is most corrupt in the veins, of the which the members are fed by sucking of blood, and seeketh thereby corruption and sickness incurable. Also the vein of the arm is oft grieved, constrained and wranged, opened and slit, and wounded, to relieve the sickness of all the body by hurting of that vein.