Abigail "Abby" Loraine Hensel and Brittany "Britty" Lee Hensel (born March 7, 1990) are dicephalic parapagus twins, meaning that they are conjoined twins of whom each has a separate head, but whose bodies are joined. They are highly symmetric, giving the appearance of having just a single body with little variation from normal proportion. In fact, several vital organs are doubled up, each twin having a separate heart, stomach, spine and spinal cord.
Each twin controls her half of their body, operating one of the arms and one of the legs. This means that as infants, the initial learning of physical processes that required bodily coordination, such as clapping, crawling, and walking required the cooperation of both children. While each is able to eat and write separately and simultaneously, activities such as running and swimming must be coordinated and alternate symmetrically. Other activities as diverse as brushing hair and driving a car require that each twin perform a sequence of quite separate actions that coordinate with the other.
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Each of the twins manages one side of their conjoined body. The sense of touch of each is restricted to her body half; this shades off at the midsagittal plane such that there is a small amount of overlap at the midline. They are effective in cooperatively using their limbs when both hands or both legs are required. By coordinating their efforts, they are able to walk, run, swim and ride a bicycle normally all tasks that they learned at a normal speed. Together, they can type on a computer keyboard at a normal speed and drive a car.