Flying yang vessel starts from Feiyang acupoint which is at bladder meridian and it should be the second branch of collateral of main meridian. It runs obliquely upward along medial aspect of lower limps and passes kidney meridian then connects with yin link vessel and runs together. If it causes disease, it will be lumbago and appear sorrow and fear when pain. It can be treated by acupuncture.

Flying yang vessel starts from which meridian? According to the original context it joins yin link vessel before foot-shao yin, so it proves flying yang vessel is neither foot-shao yin meridian nor yin link vessel. Dan poyuan thinks it is collateral that Ligou acupoint of liver meridian diverges. But the acupoint is on anterior aspect of bladder meridian, kidney meridian and yin link vessel and is inconsistent with the original context. It is reasonable that flying yang vessel is collateral of branch of bladder meridian. "Feiyang" is adjective word in ancient and it describes walking quickly with dust behind, so Feiyang is named on gastrocnemius which is related with speed of walking. Because the Feiyang acupoint is at bladder meridian so changes the name Feiyang into flying yang and Feiyang is not only name of acupoint but also name of position. "Flying yang" and "Feiyang" are in common use. Starting from Feiyang so called flying yang is general rule of designate of meridians and collaterals.

Distribution of flying yang vessel: Feiyang is distribution area of bladder meridian and collateral of bladder meridian diverges from Feiyang. There is record in Miraculous Pivot. Meridians and collaterals, that collateral of bladder meridian is at Feiyang acupoint. It diverges only one branch and communicates with meridians in internal and external relation, and there is no second branch which connects with other position, so flying yang vessel should be the second branch of collateral of bladder meridian. Diverging from Feiyang, each medial aspect runs obliquely upward then joins yin link vessel at anterior aspect of kidney meridian and runs together. Kidney meridian is at anterior aspect of bladder meridian and yin link vessel is at anterior aspect of kidney meridian, so it runs to anterior aspect of kidney meridian and joins yin link vessel.