Persistent median artery may explain the transition from 11 to 12 meridians in ancient Chinese medicine.

Persistent median artery (PMA) has been recognized as a major arterial variant of the forearm in about 30% adults and it also shows a continuously increasing trend in the last two hundred years. This may explain well the mystery why a "new meridian" was added to the older 11-meridian system over two thousand years ago in Chinese medicine. The 12th meridian, Hand Jue Yin Meridian, happens to run along the same pathway as PMA.
(© 2021 Anatomical Society.)