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.
A big blood vessel, called the portal vein, carries nutrient-rich blood from your small intestine directly to your liver. Hepatic cells make up about 60 percent of your liver tissue. These specialised liver cells carry out more chemical processes than any other group of cells in your body.