《龙虎真丹经》曰∶真龙真虎所在、所交之处，古今秘
而不说。唯《太一真书》，是太上亲着，又《真一元解入言玄言》二集，称“龙虎真诀”，一在昆仑五城
之内，一在北极大渊之内。藏之玉函，刻之金札，封之以金泥，印以玉章。猛兽列卫，神人在旁，尘世
无缘而知矣。
太白真人曰∶五行颠倒术，龙从火里出。五行不顺行，虎向水中生。少则少矣，妙则妙矣，乃所
以泄天地之机。
吕公曰∶因看崔公入药境，令人心地转分明。阳龙言向离中出，阴虎还于坎上生。二物会时为
道本，五方行尽得丹名。修真上士如知此，定跨赤龙归玉京。《入药镜》曰∶肾中生气，气中暗藏真
一之水，名曰阴虎。心中生液，液中暗藏正阳之气，名曰阳龙。龙虎非肝肺也，乃玄之又玄，知之修炼而
为圣。《传道集》曰∶肾气传心气，积气生液，液中有正阳之气，名曰阳龙，是谓出于离宫。心液传
肾液，积液生气，气中有真一之水，名曰阳虎，是谓生于坎位。二物会时，在人生人，在己生神龙虎。
古今有识者，或以多知广记，知其龙不在肝，而虎不在肺，如何得达交会之时，而悟采取之法。故少有
不长生与成仙者，良以此也。
《西山记》曰∶水火既济，龙虎相交，所用不一。如肾气传肝气，肝气方生，肾之余阴入脾，
其气过肝，为纯阳。气中有真一之水，以到于心，和气生液，颗颗如悬珠垂露，而还下田，更不随溺水以传
膀胱。若用火候无差，炼而为一气，气中生气，浩劫不死，而为陆地神仙。是虎交于龙，以肾气
合心气是也。及夫下火，加减有时，抽添有数，以心气合于肾气，是龙交于虎。若以下关透而起自尾闾穴，
左升者为龙，右起者为虎。气从夹脊双关而过，至分道岭而阳龙之气入内院，阴虎之气入天池。左
旋右盘，三十六数，而真水下降，如
甘露入心。此是龙虎相交于上宫，又不必于心肾而有上交、上合之别也。及夫胎完胎就，而真气既生，
防其大过，必济之以水，而玉液金液还丹。及夫还丹日久，行于经络，而变阳酥，凝于中府，而积
白雪，防其大过，必举以火，而有炼质焚身。是知还丹之时，乃阴虎单行，而不必交于龙也。焚质
之时，乃阳龙独举，而不必交于虎也。龙虎之功，不为小矣，所患乎不知龙虎之本也。若识龙虎之象，
又知交合之时，且得采取之法，三百日养成内丹，而命中有晶，乃得与天地齐其寿算矣。
According to the *True Dragon and Tiger True Elixir Scripture*: The location of the true dragon and true tiger, and the place where they intersect, have been kept secret by ancient and modern times without being revealed. Only the *Taiyi Zhen Shu* (Supreme One True Book) was personally written by Taishang Laojun (The Supreme Venerable One). Additionally, the two collections titled *Zhenyuan Yijie Ru Yan Xuan Yan* refer to the "True Secret of Dragon and Tiger." One is located within the Five Cities of Kunlun, and the other is within the Great Abyss of the North Pole. These texts are stored in jade caskets, inscribed on gold tablets, sealed with golden mud, and stamped with jade seals. They are guarded by rows of fierce beasts and attended by divine beings; those in the mundane world have no opportunity to know them.
Daibai Zhenren (Immortal White Venus) said: In the art of reversing the Five Phases (Wu Xing), the dragon emerges from fire. If the Five Phases do not proceed in their normal order, the tiger is born from water. Although these words are few, they are profoundly subtle; this is how the mechanism of heaven and earth is revealed.
Master Lü said: By reading Cui Gong's *Ru Yao Jing* (Mirror for Entering the Medicine Realm), one's mind becomes clearer. The Yang Dragon is said to emerge from Li (the trigram for Fire/Heart), and the Yin Tiger is born from the upper part of Kan (the trigram for Water/Kidney). When these two substances meet, it constitutes the root of the Dao. When the energies of the five directions are fully circulated, the name of the Golden Elixir is obtained. If high-level cultivators understand this, they will surely ride a red dragon back to Yu Jing (Jade Capital). The *Ru Yao Jing* states: Qi is generated in the Kidneys; hidden within this qi is the True One Water, named the Yin Tiger. Fluids are generated in the Heart; hidden within these fluids is the True Yang Qi, named the Yang Dragon. Here, "Dragon" and "Tiger" do not refer to the Liver and Lungs, but to something profound and mysterious; knowing and cultivating this leads to sainthood. The *Chuandao Ji* (Collection of Transmission) states: Kidney Qi transmits to Heart Qi; accumulating Qi generates fluids. Within these fluids is True Yang Qi, named the Yang Dragon, which is said to originate from the Li Palace (Heart). Heart fluids transmit to Kidney fluids; accumulating fluids generates Qi. Within this Qi is the True One Water, named the Yin Tiger (Note: Original text says Yang Tiger here, but contextually refers to Yin Tiger in Kan position), which is said to be born at the Kan position (Kidney). When these two substances meet, in humans it produces a True Person, and in oneself it produces Divine Dragon and Tiger. Scholars throughout history, relying on extensive knowledge and memory, knew that the Dragon is not in the Liver and the Tiger is not in the Lungs. However, how could they reach the time of intersection and comprehend the method of extraction? Therefore, very few achieve immortality or become immortals, precisely for this reason.
The *Xishan Ji* (Record of Western Mountain) states: When Water and Fire are mutually accomplished (Ji Ji), Dragon and Tiger intersect, and the methods used vary. For instance, when Kidney Qi transmits to Liver Qi, as Liver Qi begins to generate, the residual Yin of the Kidney enters the Spleen. This Qi passes through the Liver, becoming Pure Yang Qi. It contains True One Water, which reaches the Heart. Harmonious Qi generates fluids, droplet-like hanging pearls and dripping dew, which then return to the Lower Dantian, no longer following the urine to transmit to the Bladder. If the firing methods (huohou) are error-free, refining into one Qi, generating Qi within Qi, one remains immortal through kalpas and becomes an Earthly Immortal. This is Tiger intersecting with Dragon, combining Kidney Qi with Heart Qi. When lowering the fire, there are times for addition and subtraction, and numbers for drawing and adding. Combining Heart Qi with Kidney Qi is Dragon intersecting with Tiger. If rising from the Xiaguan point through the Weilu acupoint, ascending to the left is Dragon, and rising to the right is Tiger. The Qi passes through the double Guan points of the Jiaji spine, and at Fendaoling, the Qi of Yang Dragon enters the Inner Courtyard, and the Qi of Yin Tiger enters Tianchi. Rotating left and coiling right, thirty-six times, True Water descends like sweet dew entering the Heart. This is Dragon and Tiger intersecting in the Upper Palace (Head/Niwang Palace), without needing to distinguish between upper intersection and upper combination regarding Heart and Kidney. When the fetal stage is complete and the fetus formed, and True Qi has arisen, to prevent excess, it must be balanced with Water, resulting in Jade Fluid and Golden Fluid returning elixir. After the returning elixir has been practiced for a long time, moving through the meridians, it transforms into Yang Su (Yang Butter); condensing in Zhongfu, it accumulates White Snow. To prevent excess, it must be raised by Fire, leading to the process of refining substance and burning the body. Thus, it is known that during the returning elixir stage, the Yin Tiger moves alone, without needing to intersect with the Dragon. During the substance-refining stage, the Yang Dragon rises alone, without needing to intersect with the Tiger. The merit of Dragon and Tiger is not small; the worry lies in not knowing the root of Dragon and Tiger. If one recognizes the image of Dragon and Tiger, knows the time of intersection, and obtains the method of extraction, cultivating the Internal Elixir over three hundred days, a crystal (elixir) forms in destiny, allowing one to share the lifespan of Heaven and Earth.