Lymph, lymph ducts and lymph glands together are called the lymphatic system. Because the lymphatic system circulates fluid throughout the body, it is sometimes called the secondary circulatory system. In 1960 Danish scientists Olus Rudbeck and Thomas Bartholin first described the human lymphatic system. Wuchereria bancrofti worm infestation causes abnormal swelling of lymph ducts and lymph glands. It is called milk disease or filaria or elephantiasis.