Added to these 12 meridians are eight vessels that in acupuncture theory store up the excess of energy, to restore it to circulation when needed. They are as follows:
1. The governing vessel. This is the meridian Tu MO, of moral and intellectual energy. It is a Yang meridian.
2. The vessel of conception. This is the meridian Jenn MO, of the genitourinary organs, digestive functions, and respiratory functions. It is a Yin meridian.
These two meridians communicate between themselves, but are independent of the others. Finally there are six vessels called the Marvelous Vessels, Extraordinary Vessels, or Curious Meridians: three Yang ones—Yang Keo, Yang Oe, and Tae MO; three Yin ones—Yin Oe, Chong MO and In Keo.