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.
The lymphatic tissue includes the lymph nodes, spleen, tonsils, adenoids and the thymus (an organ in the chest that is particularly large during infancy). In medicine, a tissue is a broad term that is applied to any group of cells that perform specific functions. A tissue in medicine need not form a layer.