Blood-Vessels, in anatomy, are long membranous canals, which convey the blood through every part of the body. They are divided into two classes, arteries and veins. For an account of the construction, situation, and uses of the former, see Artery.

The veins originate from the extremities of the arteries, and return the blond from them into the auricles of the heart, which is the common termination of all the veins. Like the arteries, the veins are also composed of three membranes, but more delicate than those of the former, and nearly transparent; they are divided into trunks, branches, ramuli, etc. In general, the veins are situated by the sides of the arteries, but more superficially; and as they proceed towards the heart, they gradually become larger. As the veins do not pulsate, the blood, which they receive from the arteries, is urged forward partly by the contractility of their coats, partly by the pressure of the blood from the arteries, and partly by respiration. They are moreover furnished with valves, which prevent the return of the blood. - See Blood.