Kidneys, historical anatomical artwork. This dorsal (back) view shows the kidneys and associated nerves lying outside the peritoneum (membrane lining the abdominal cavity). The kidneys (centre left and right) each have an adrenal gland on top. The nerves (white) form part of the body's autonomic nervous system, controlling the involuntary functions of the kidneys. Also seen are the renal arteries (red) supplying blood to the kidneys, and the vena cava (blue, vertical), the largest vein in the body. This illustration is taken from the 19th century French textbook The Atlas of Human Anatomy and Surgery by J. M. Bourgery and N. H. Jacob.