Thumb anatomy, 19th-century illustration. This vertical section passes through the centre of the thumb, with the nail and its nailbed and root at upper right, and the top two finger bones (distal and intermediate phalanges, white) down centre. The outer skin layer is the epidermis (grey), with the dermal papillae and nerves (red) below that. Some fat tissue (yellow) is present. The thumb's flexor tendon (blue) is at left, next to the bone. Cartilage is shown at the articulation between the two phalanx bones. The labels are in French. Published in 'La Vie Normale et la Sante' (Normal Life and Health, Paris, 1881) by Dr Jules Rengade.