Preface
Recently, the new semester has gotten on track, with outpatient, emergency, and elective classes rotating in turn. I still want to find time to study during night emergency shifts, and the pressure is gradually increasing. The update frequency of this account will drop significantly.
But! I have another account dedicated to writing fairy tales (which should count as fairy tales), serving as a channel to relieve stress. If anyone is interested, feel free to check it out.
Process
Recently, while preparing for the formula (prescription) exam, I came across a key point: Zuo Gui Wan (Left Return Pill) and You Gui Wan (Right Return Pill).
I learned the formula theory poorly back then and vaguely remembered that one of these pills mainly nourishes Yang, and the other mainly nourishes Yin.
Not clearly recalling, I checked my notes: Zuo Gui Wan nourishes kidney Yin, You Gui Wan nourishes kidney Yang. Wait, isn’t it supposed to be left rises and right descends, with the left mainly Yang and the right mainly Yin?
When encountering a confusing Traditional Chinese Medicine (TCM) question, I first asked a senior.
2023-09-15
: Senior, I have a question. Since left is Yang and right is Yin, why is Zuo Gui Wan nourishing Yin while You Gui Wan nourishes Yang?
: The left Yang right Yin comes from the concept of left rise right descent—Liver rises, Lung descends. The original text of Zuo Gui Wan says it replenishes the Yin of the left kidney, corresponding to the left Chi pulse (尺脉) on the pulse, representing kidney Yin.
Oh, so left rise right descent and left return right return are not the same thing. I get it (I think I got it)!
A few days later, I recalled the question again. Wait, then why is the left pulse presenting Yin and the right pulse showing Yang? I felt awkward to ask the senior again, so I checked the book directly. The original text is from Jingyue Quanshu (Complete Works of Jingyue); I searched the original text for Zuo Gui Wan and You Gui Wan and excerpted as follows:
Jingyue Quanshu Volume 51, Section De Ji, New Formulas, Eight Arrays, Supplement Array
Zuo Gui Wan 4: Treats true Yin deficiency and kidney water insufficiency, unable to nourish Ying and Wei, gradually leading to weakness; or virtual heat alternating chills and fever, spontaneous sweating or night sweating; or mind unsettled, blood not returning to the source; or hypofunction injuring Yin; or urinary incontinence; or qi deficiency causing dizziness; or blurred vision and tinnitus; or dry mouth and tongue; or soreness of the loins and weakness of the legs; all involved with marrow deficiency and fluid exhaustion, promptly use the ruler of water to strengthen the original Yin of the left kidney, which will replenish essence and blood automatically. This formula is the main prescription.
You Gui Wan 5: Treats original Yang deficiency, whether congenital insufficiency or excessive labor damage, causing Mingmen fire decline and inability to generate Earth, leading to spleen and stomach cold deficiency, poor appetite; or nausea and bloating; or reversing stomach Qi and food obstruction; or fear of cold; or pain in the umbilicus and abdomen; or loose stools; frequent diarrhea; or involuntary urination; cold urinary dribbling; cold hernia; or cold invading valleys causing pain and numbness in limbs and joints; or cold in the lower burner with water accumulation and edema. In general, those with true Yang deficiency experience fatigue and weakness of Qi; or palpitations; or limbs unable to retract; or sight of evil spirits; or Yang decline with no offspring. Promptly nourish the original fire to strengthen the original Yang of the right kidney so the spirit and Qi are strong. This formula is the main prescription.
This section only verifies that Zuo Gui Wan nourishes left kidney Yin and You Gui Wan nourishes right kidney Yang. Not enough, so I continued looking.
Jingyue Quanshu Volume 5, Pulse Spirit Chapter, Part Location Explanation II
Left Cun (寸) corresponds to the heart, sensing the heart and pericardium, receiving the southern sovereign fire Qi, nourished by spleen Earth, restrained by lung Metal, corresponding to clarity and turbidness of the spirit.
Right Cun corresponds to the lung, sensing the lung and mediastinum, receiving the western dry Metal Qi, nourished by kidney water, restrained by liver Wood, governing emotions such as good and evil.
The above two parts are considered upper sensing locations; thus, diseases of the head, face, throat, mouth, teeth, neck, shoulders, and back are sensed here.
Left Guan (关) corresponds to the liver, sensing liver and gallbladder, receiving eastern wind wood Qi, nourished by heart fire, restrained by spleen Earth, governing official rank and wealth.
Right Guan corresponds to the spleen, sensing spleen and stomach, receiving central damp Earth Qi, nourished by lung Metal, restrained by kidney water, governing wealth and fortune.
The above two parts are in the middle, sensing the middle burner, thus diseases of hypochondria, ribs, abdomen, and back.
Left Chi (尺) corresponds to kidney, sensing kidney, bladder, and large intestine, receiving northern cold water Qi, nourished by liver Wood, restrained by heart Fire, responsible for Yin Qi and longevity.
Right Chi corresponds to triple burner (San Jiao), sensing kidney, triple burner, Mingmen (Life Gate), and small intestine, receiving northern heavenly fire Qi, nourished by spleen Earth, restrained by lung Metal, responsible for Yang Qi and longevity.
The above two are the lower sensing locations; thus diseases related to waist, abdomen, genitals, and legs are sensed here.
This part verified that pulse diagnosis is indeed done this way: left representing kidney Yin, right representing kidney Yang. Still not enough, so I continued investigating. Luckily, the following text mentions:
Jingyue Quanshu Volume 5, Pulse Spirit Chapter, Part Location Explanation II
Someone asked: Why is the right chi Yang and belongs to Fire? It is said that the chi is the home of the Snake Warrior, located in the rigid northwest; thus, the right side of hand and foot is stronger than the left, which is the meaning of left Yin right Yang. This chapter has a detailed explanation in Leijing · Qiuzhenglu to be referenced.
I turned to Leijing, unfolded the explanation 
Leijing Tuyi Qiuzhenglu
Each of the five organs has one side, but the kidney has two. Because it has two, their images are different. Like the ears and eyes are one, but the left is clearer than the right; hands and feet are one, but right is stronger than left.
So the northern deity has a Snake Warrior; the snake represents Yang, and the warrior represents Yin. The two chi pulses are divided into left and right; left governs water, right governs fire.
The principle of left Yang right Yin is usual, but this text says left water right fire—why is that? The kidney belongs to the Rat (child) sign, Qi corresponds to the winter solstice, in a position dividing Yin and Yang evenly. From the winter solstice onward, the heavens rotate leftward and the time is spring; the Big Dipper belongs to the wood branch; the sun and moon move rightward and coincide with Hai; Chen next to Zi; as Yang advances one month, the meeting retreats one palace, and the sun gradually moves to the right, so humans correspond accordingly.
Thus water on the right turns to fire. Also, the four limbs of humans correspond to the earth; the rigidness of earth is in the northwest, so it is reasonable that the right chi is Yang.
emmm, the explanation I can understand and accept is that humans are right-handed, so the right side is stronger than the left; therefore right is Yang and left is Yin. I do not understand or accept the other reasons.
Senior: For the left liver to rise, it must have a source; that source is liver and kidney Yin—using Yin in substance and Yang in function. The right lung to descend must contract, which is called “Su,” matching the kidney’s sealing and containment function; if the kidney fails to receive Qi and Qi is short, it is extreme kidney Qi deficiency; thus kidney Yang is on the right.
I find the senior’s explanation more convincing. By now, I have spent a full hour (ignoring other unrelated literature I came across). I feel I am getting stuck in a loop; I will understand as much as I can and stop here for now. I will revisit this issue in the future.
Follow-up
Recently, the senior wrote an article to further explore “left rise right descent” 
“The Underlying Logic of ‘Left Rise Right Descent’”
We discussed this question again:
You want to thoroughly understand TCM physiology? Let me think. It should be related to the kidney’s reabsorption.
emmm, as you can see, we actually still do not fully understand.
Many issues are not easy to grasp quickly due to limited ability or biased thinking (maybe integrating Chinese and Western medicine is off track? Maybe internal evidence approach is more suitable?). Regardless, the process of thinking is the most important—constantly posing questions and reflecting. This way, the brain is continuously exercised, like sharpening a knife.
When you have to make quick decisions facing real problems, a sharp knife will cut neatly and efficiently compared to a dull one!
Sharing this process also aims to share one concept: TCM is everywhere to learn. Don’t consider review a waste of time. Without this opportunity, I might still not have systematically reviewed this part of Jingyue Quanshu until now.
Of course, research is research, exam preparation is exam preparation—don’t fail the exam 