At a glance
The vessel running up the front of the body. In this chapter it ‘opens’ (通) when the heavenly water arrives and ’empties’ (虛) at seven sevens: the vessel is what carries the schedule, not what sets it.
任 is a verb before it is a name: to bear, to be charged with an office. As a vessel name it is usually rendered “conception vessel”, which is the sense the chapter leans on — this is the vessel that opens when the heavenly water arrives.
Its two states in this passage are 通 (open, flowing) and 虛 (empty). The chapter gives no mechanism; it gives a schedule and a vessel that follows it.
Passages where the term does real work, with the original, pinyin and English on the same line.
Every rendering below is a decision about which reader is being addressed. There is no neutral option.