What is the enlightenment and application of the twelve meridians in Huangdi Neijing?

In Huangdi Neijing, there is a passage in the spirit pivot, which clearly describes the direction of the twelve meridians:

"Three points Yin hand, since the dirty hand; The third yang of the hand, walk from the hand; The foot of three yang, the first line; Foot three yin, self-sufficient to the abdomen. "

"Dirty" in the original text refers to "chest". This article expounds four laws of the twelve meridians's walking direction:

(1) The Three Yin Meridian of the Hand starts from the chest, reaches the tip of the finger, and passes through the Three Yang Meridian of the Hand;

There are lungs, heart and pericardium in the chest, and the corresponding three yin meridians are the lung meridian of hand Taiyin, the heart meridian of hand Shaoyin and the pericardium meridian of hand Jueyin. The Sanyinjing of the hand circulates from the chest along the inside of the arm to the end of the finger.

(2) The three Yang meridians of the hand all start from the tip of the finger, reach the head and face, and intersect with the three Yang meridians of the foot;

The three yang meridians of the hand run from the ends of the fingers to the head and face. Because the three yin meridians of the hand extend from the chest to the tip of the finger, and then the three yang meridians of the hand, that is, the large intestine meridian of the hand Yangming, the small intestine meridian of the hand Taiyang, and the triple energizer meridian of the hand Shaoyang, all extend from the tip of the finger to the head and face, and the three yang meridians of the hand also terminate.

(3) The Foot Sanyang Meridian starts from the head and face, reaches the toe end, and meets the Foot Yin San Meridian;

Foot Sanyang Meridian is Foot Yangming Stomach Meridian, Foot Shaoyang Gallbladder Meridian and Foot Taiyang Bladder Meridian. These three yang meridians extend from the head to the toe, where the toe refers to the toe. After reaching the toe, the three Yang meridians of the foot also terminate, and the three Yin meridians of the foot intersect downward after termination.

(4) The Three Yin Meridian of the Foot starts from the toe, reaches the abdominal cavity and chest cavity, and intersects with the Three Yin Meridian of the Hand.

The three yin meridians of the foot are the spleen meridian of the foot Taiyin, the liver meridian of the foot Jueyin and the kidney meridian of the foot Shaoyin. The three yin meridians of the foot need to circulate from the foot to the abdomen, and finally the three yin meridians of the foot go up again, from the abdomen to the chest, until the chest intersects with the three yin meridians of the hand.

This constitutes a circular path of "the intersection of Yin and Yang, like endless rings" (Lingshu Nutrition Health Club).