"The inferior accessory fissure of the lung, also known as Twining's line, divides the medial basal bronchopulmonary segment from the rest of the lower lobe 4."
"The line on CXR was described by British radiologist Edward Wing Twining (1887-1939), who also described Twining's line of the posterior cranial fossa 5."
"This accessory fissure is present in ~12% of people when examined with CT 3 and is visible on 8% of PA chest x-rays 4. It is approximately five times more common on the right than the left."