The species theory, polygenism, held that human races were of different lineages and suggested a hierarchy outlined in the Chain of Being that positioned Africans between man and lower primates.
No, they are involved in the Circulatory System which is responsible for pumping and channelling blood to and from the body and lungs with heart, blood and blood vessels. no veins are not considered an organ because they are a grouping of different tissues like a organ.
Graft. Also called: AV graft, arteriovenous graft. The graft is similar to a fistula, in that it is also an under the skin connection of an artery and vein, except that with a graft, a man-made tubing connects the artery and vein. The soft, plastic-like tube is about one-half inch in diameter and is made from a type of TeflonÂ® or Gore-TexÂ® material. Transplanted animal or human vessels may also be used as grafts to connect an artery and vein. Grafts are usually placed in the arm, but can also be placed in the thigh. Grafts do not require as much time to mature as fistulas, because the graft does not need time to enlarge before using.