da Vinci's Seat of the Soul

Research:  The Involuntary Motion of the Sacrum Between the Ilia.

It is an anatomical fact that the sacrum (tail bone) moves between the ilia (bones of the pelvis). It simply would not be possible for humans to walk or run if the sacral-iliac joints did not allow for motion.

Yet for centuries it was believed by scientists that the pelvis was a solid array of bone and that there was no independent motion of the sacrum. This erroneous belief was still held by most of the medical community in the first part of the 20th century. History may in fact be repeating itself in the debate over cranial bone motion, just as the sacrum was once considered immobile.

According to the PRM model, the sacrum also moves involuntarily between the ilia, around a respiratory axis. What remains controversial about this type of sacral motion, is the driving force or cause.


It is now a well-established fact the sacrum moves between the ilia. Ambulatory and respiratory motions have each been demonstrated. Further research is required to understand the relationship between involuntary motion of the sacrum and motion of the cranial bones.


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