the Breath) chapter describes circulating breaths between the upper and lower dantians (丹田, "elixir fields"): Niwan dantian (泥丸丹田, "muddy pellet elixir-field", or naotian 腦宮 "brain palace") and Xia dantian (下丹田, "lower elixir-field", above the perineum). There are two points on the spine behind the lower [dantian]. They correspond through the ridge vein with the [niwan dantian] which is the brain palace (a point between the eyes above the root of the nose). The Original Breath [yuanqi] is obtained by storing (the breath of) every three consecutive swallowings in the lower [dantian]. Use the mind to take (the Original Breath) in and to make it enter the two points. (You should) imagine two columns of white breath going straight up on both sides of your spine and entering the [niwan] to becloud thickly the palace. Then the breath continues to your hair, your face, your neck, both arms and hands up and to your fingers. After a little time, it enters the chest and the middle [dantian] which is (by) the heart. It pours on into the five viscera, it passes the lower [dantian], and reaches [sanli 三里] (the Three Miles, i.e., the genitals) It goes through your hips, your knees, ankles and all the way to the [yongquan 涌泉] (acupuncture points) which are in the center of your feet soles. That is the so-called [謂分一氣而理] "to share one breath and manage it individually". (tr. Huang 1988: 18-19) The late 8th-century Taiwu xiansheng fuqi fa (太無先生氣服氣) explains how to circulate the yuanqi Original Breath. Tang Daoist practitioners fundamentally changed the nature and understanding of taixi Embryonic Breathing from the ancient theory of waiqi 外氣), "external qi of the air; external breathing") to the new theory of neiqi (內氣, "internal qi") of one's organs; internal breathing"). Instead of inhaling and holding waiqi breath, adepts would circulate and remold visceral neiqi energy, which was believed to recreate the yuanqi (元氣 "prenatal qi; primary vitality") received at birth and gradually depleted during human life. According to the Taiwu xiansheng fuqi fa, since it is the Original Breath and not external breath which must be kept circulating through the body, and since its natural place is within the body, there is no need to make it enter or hold it in by effort as the ancients did: no retention of the breath, which is exhausting and, in some cases, harmful. But it does not follow