amount of overlap at the midline. Stomach aches, however, are felt by only the twin on the opposite side. They cooperatively use their limbs when both hands or both legs are required. By coordinating their efforts, they walk, run, swim, play volleyball and the piano, and ride a bicycle normally. Together, they can type on a computer keyboard and drive a car. However, Abby, at , is taller and longer of leg than Brittany, who is and their disparate heights caused difficulty in balancing a Segway, as shown in their 2012 reality series. Organ distribution The twins have individual organs in the upper part of their body, while most of those at and below the navel are shared, the exception being the spinal cord. 2 heads 2 spines merging at the coccyx and joined at the thorax by sections of ribs. Surgery corrected scoliosis. 2 completely separate spinal cords 2 arms (originally 3, but the rudimentary central arm was removed, leaving the central shoulder blade in place) 1 broad ribcage with 2 highly fused sternums and traces of bridging ribs. Surgery expanded the pleural cavities. 2 breasts 2 hearts in a shared circulatory system (nutrition, respiration, and medicine taken by either affects both) 4 lungs with the medial lungs moderately fused, not involving Brittany's upper right lobe; three pleural cavities 1 diaphragm with well coordinated involuntary breathing, slight central defect 2 stomachs 2 gallbladders 1 liver, enlarged and elongated right lobe Y-shaped small intestine, with slightly spastic double peristalsis at the juncture 1 large intestine (one colon, rectum, and anus) 3 kidneys: 2 left, 1 right 1 bladder 1 set of reproductive organs 2 separate half-sacrums, which converge distally 1 slightly broad pelvis 2 legs Separation Upon their birth, the twins' parents decided not to attempt surgical separation after hearing from doctors that it was unlikely that both would survive the operation. As the twins grew and learned to walk and develop other skills, their parents confirmed their decision against separation, arguing that the quality of life for the surviving twin or twins living separately would be less than their quality of life as conjoined people. Adulthood Dicephalic parapagus twins rarely survive into adulthood. As teenagers the twins both passed their written and practical driver's license exams separately because, although driving requires coordination between them, state law required that they each be licensed. Abby controls the devices on the right