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.
Tracheids and vessel members are referred to as tracheary elements. Phloem vascular tissue contains parenchyma and has two types of cells that assist in the transport of food: sieve-tube members and sieve cells. Sieve-tube members are more specialized and are present in advanced flowering seed plants. Learn more about Human Anatomy