The central drainage and metabolic organs strung along the lymph vessels. The mesenchymal structure is native, being present at birth. The functional cells have all migrated there, some recently from the marrow, spleen, thymus or blood, others have resided since a few months after birth. Much of the antibody memory is stored in these nodes, and having only venous blood supply, lymph nodes are constantly shunting metabolised substances back into the blood, so the final lymph drainage from the thoracic duct into the left subclavian vein (or the right subclavian) contains fluid already screened and cleansed by many nodes.