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The *Dai* pulse (Intermittent Pulse) is observed during its beating, characterized by a slow rhythm with pauses that subsequently resume.
In healthy individuals, this pulse is generally unfavorable, except during pregnancy when it nourishes the fetus.
(The *Jie* pulse (Knotted Pulse) and *Cu* pulse (Rapid Intermittent Pulse) have irregular pauses; sometimes stopping after two beats, or after three to five beats before resuming. In contrast, the *Dai* pulse has regular pauses, strictly following a specific count before stopping. After the pause, the pulse qi returns to the *Chicun* position (radial artery at the wrist), taking a considerable time to resume beating.
Hua Boren stated: "If there is no disease but the body is emaciated, the appearance of a *Dai* pulse indicates a critical condition." If there is disease and the vital qi cannot continue, the *Dai* pulse is a pathological pulse. In *Shanghan* (Cold Damage) diseases, if palpitations occur with a *Dai* pulse, *Fumai Tang* (Decoction for Reviving the Pulse) should be administered. During pregnancy, if a *Dai* pulse appears, it indicates the fetus is one hundred days old. The distinction between life and death associated with the *Dai* pulse must not be overlooked.)

The *Du* vessel (Governing Vessel) and *Ren* vessel (Conception Vessel) run through the center of the body; seeking the source of immortality within them reveals a path.
By distinguishing the boundaries of the *Yangwei* (Yang Linking) and *Yinwei* (Yin Linking) vessels from the *Qiao* (Heel) vessels, one can regulate the *Chong* (Penetrating) and *Dai* (Girdle) vessels, akin to stoking the furnace fire until it glows red.
The Eight Extraordinary Vessels refer to the *Du* vessel, *Ren* vessel, *Yangwei* vessel, *Yinwei* vessel, *Yangqiao* vessel, *Yinqiao* vessel, *Chong* vessel, and *Dai* vessel. Because they do not adhere strictly to the twelve regular meridians, they are called "Extraordinary" (*Qi*). The *Du*, *Ren*, and *Chong* vessels all originate from the *Huiyin* acupoint (CV1, Confluence Point), branching out as three vessels from one source. The *Du* vessel passes through the *Changqiang* acupoint (GV1, Long Strong), ascends along the spine, crosses the vertex, and terminates at the *Yinjiao* acupoint (GV28, Gum Intersection); it serves as the commander of all Yang vessels, hence termed the "Sea of Yang Vessels." The *Ren* vessel ascends along the umbilical region and abdomen, passes through the throat, and terminates at the *Chengjiang* acupoint (CV24, Receiving Pool); it bears the Yin vessels, hence termed the "Sea of Yin Vessels." The *Yangwei* vessel originates from the convergence of all Yang meridians, starting from the *Jinmen* acupoint (BL63, Metal Gate) at the lateral malleolus, and ascends within the *Wei* (Defensive) level. The *Yinwei* vessel originates from the convergence of all Yin meridians, starting from the *Zhubin* acupoint (KI9, Building Guest) at the medial malleolus, and ascends within the *Ying* (Nutritive) level. The meridians and collaterals of the human body are dense and complex; these two vessels provide a binding constraint at the intersections of Yin and Yang, acting as the main rope that gathers the meshes, thereby maintaining the balance of Yin and Yang. The *Yangqiao* vessel originates from the heel, follows the lateral malleolus, and ascends on both sides of the body, enabling agile movement of the joints. The *Yinqiao* vessel originates from the heel, follows the medial malleolus, and ascends on both sides of the body, also facilitating joint agility. The *Chong* vessel runs forward in the abdomen, backward in the back, upward to the head, and downward to the feet, reaching every part of the tendons, bones, spleen, and flesh. It is the crucial passage for the ascending and descending of the twelve meridians, hence called the "Sea of the Twelve Meridians." The *Dai* vessel encircles the waist horizontally, resembling a belt, thereby girdling and controlling all other vessels. If physicians understand the Eight Extraordinary Vessels, they grasp the essence of the twelve meridians and fifteen collaterals; if cultivators understand them, they enter the door to the mysteries of the ascent and descent of Dragon and Tiger, and the opening of hidden portals. For health preservation, during leisure time, one may raise the Qi of the *Du* vessel, following the *Weilu* (Tailbone), *Jiaji* (Vertebral Process), and *Shuangguan* (Double Pass) points, ascending to the brain crown, then descending to connect with the *Ren* vessel. This cycle repeats endlessly, beginning and ending anew. With prolonged regulation of breathing, the two vessels merge into one. The primordial Yang Qi of the body arises from below and exhausts from below. Since the *Du* and *Ren* vessels are linked and their transport never ceases, given their source of generation, they are difficult to deplete, ensuring stability of lifespan! Deer looking back at their tails can unblock the *Du* vessel; turtles drawing breath through their noses can unblock the *Ren* vessel. These two animals achieve longevity, which is clear evidence. Raising the *Du* vessel causes the *Yangwei* and *Yinqiao* vessels to ascend with it; unblocking the *Ren* vessel causes the *Yinwei* and *Yangqiao* vessels to descend with it. Through this ascent and descent, the *Yangwei*, *Yinwei*, *Yangqiao*, and *Yinqiao* vessels also become smooth and unobstructed. Thus, starting from the *Huiyin* acupoint, moving up to heaven and down to the abyss, one operates the *Chong* vessel; starting from the *Jilei* (Costal Margin) area, turning left thirty-six times and right thirty-six times, one operates the *Dai* vessel. One observes that when Ying and Wei harmonize, the complexion becomes increasingly moist and lustrous; when joints function smoothly, hands and feet become increasingly light and agile. The 360 bone joints become bright and polished; the 84,000 hair pores become open and unobstructed. Blood flows without stagnation or obstruction; Qi circulates without stoppage. The Six Evils (Pathogenic Factors) cannot invade, and the Seven Emotions cannot harm. There is no method better than this for warding off disease and prolonging life. Why is it necessary to gather the lingzhi mushrooms of Shang Mountain or collect dew from bronze plates to achieve eternal life? From this, we know that the secret of longevity in the Purple Mansion lies entirely within the Eight Extraordinary Vessels.
(The *Cantong Qi* states: "The River Cart of the North refers to this method. Practicing it diligently unblocks meridians and smooths vessels, promoting health; pursuing it further retrieves essence and gathers Qi, extending years; illuminating it spiritually and applying the methods of 'advancing fire' and 'retreating lead,' one can refine the Elixir.")
All techniques transmitted in immortal classics—such as extracting Lead and adding Mercury, subduing the Dragon and taming the Tiger, capturing birds and catching rabbits, snow falling producing lotuses—are contained within this system. Those with shallow understanding gain shallow benefits; those with deep understanding gain profound benefits.