Yin and Yang is perhaps the most fundamental concept in Chinese Medicine, as it is the foundation of diagnosis and treatment.

Yin  female, passive, negative principle in nature  the moon. shaded orientation north or shady side of a hill south of a river.

Yang  positive, active, male principle in nature, south or sunny side of a hill , north of a river.

There are four things you can say about them:

1. Yin-Yang are opposites
   They are either on the opposite ends of a cycle, like winter and summer or midnight and high noon. This opposition is relative, and can only be spoken of in relationships. For example: Water is Yin relative to steam but Yang relative to ice. Yin and Yang are never static but in a constantly changing balance.
2. Interdependent: Can not exist without each other
   The Tai Ji (Supreme Ultimate) diagram shows the relationship of Yin & Yang and illustrates interdependence on Yin & Yang. Nothing is totally Yin or totally Yang. Just as a state of total Yin is reached, Yang begins to grow. Yin contains seed of Yang and vise versa. They constantly transform into each other. For Example: no energy without matter, no day without night.
   The classics state: “Yin creates Yang and Yang activates Yin”.
3. Mutual consumption of Yin and Yang
   Relative levels of Yin Yang are continuously changing. Normally this is a harmonious change, but when Yin or Yang are out of balance they affect each other, and too much of one can eventually weaken (consume) the other.Four (4) possible states of imbalance:
   1. Too much Yin
   2. Too much Yang
   3. Not enough Yin
   4. Not enough Yang
4. Inter-transformation of Yin and Yang.
   One can change into the other, but it is not a random event, happening only when the time is right. For example: Spring only comes when winter is finished.

 

Yin	Yang
Front (chest-abdomen)	Back
Body	Head
Interior (organs)	Exterior (skin, muscles)
Below waist	Above waist
Anterior-medial	Posterior-lateral
ventral surface of the trunk and limbs	back and dorsal surface of the limbs
Structure	Function
Blood/Body Fluids	Qi
Conservation/storage	Transformation/change
Yin Organs: Heart, Lung,	Small Intestine, Lg. Intestine
Liver, Spleen, Kidney,	Gall Bladder, Stomach, Bladder
Pericardium	San Jiao
“Solid Organs”	“Hollow Organs”

 

Structure and Function

Structure = something substantial, i.e. Matter (Yin)
Function = something insubstantial, action, energy (Yang)
All parts of the body have a structure (a physical form), and a function (their activity)
However, all is relative. Even within the Yang category of function, there are Yin functions (i.e. storage, conservation) and Yang functions, i.e. transformation, transportation, digestion, excretion.
Within the Yin category of form there are Yin forms (“solid”) and Yang forms (“hollow”)

Blood, Body Fluids, and Qi

Qi is Energy, more Yang.
Blood = denser and more material (therefore Yin).
But note that “Xue” (blood) not exactly like our concept of Blood. More like “thicker” form of Qi.

Note: there are several types of Qi. Each is relatively more Yin or Yang.
Ancestral QI (more Yin, more slow moving. Moves in long slow cycles).
Ying Qi (more Yang than Ancestral Qi, moves with Blood with which it is closely related). Ying is more Yin than Wei Qi.
Wei Qi the most Yang form of Qi. Circulates in the exterior in the daytime to protect us from pathogenic influences, and regulates opening/closing of pores.

Conservation/Store (Yin) and Transformation/Change (Yang)

Yin Organs store Blood, Body Fluids, Essence, etc.
Yang Organs constantly transform, transport and excrete the products of digestion.

Solid and Hollow Organs (Zang Fu)

Yin Organs are “Solid”: constantly active, involved in production and storage of the body’s vital Substances (Qi Blood, Body Fluids, Essence)

Yang Organs are “Hollow”: receive and circulate but do not store, involved in digestion, transformation, excretion.

Clinical signs and symptoms can be interpreted via Yin-Yang theory. When Yin Yang are in dynamic balance and relating harmoniously, there are no symptoms to observe. When Yin and Yang are out of balance, symptoms can arise.
For example if Yin does not cool and nourish Yang so Yang rises (headaches, red face, sore eyes, sore throats, nosebleeds, irritability, manic behavior. Or if Yang does not warm and activate Yin (cold limbs, hypo-activity, poor circulation of blood, pale face, low energy.

 

Yin	Yang
Deficiency	Excess
Hypoactivity	Hyperactivity
Chronic disease/gradual onset	Acute disease/rapid onset
Slowly changing symptoms	Rapid pathological changes
Quiet, lethargy, sleepiness	Restlessness, insomnia
Wants to be covered	Throws off bedclothes
Lies curled up	Lies stretched out
Cold limbs and body	Hot limbs and body
Pale face	Red face
Weak voice, no desire to talk	Loud voice, talkative
Shallow, weak breathing	Coarse breathing
No thirst/wants warm drinks	Thirst esp. for cold drinks
Copious, clear urine	Scanty, dark urine
Loose stools (fluids not transformed)	Constipation (damage to fluids by heat)
Clear, copious secretions	Thick, sticky white/yellow secretions
Excessive moisture	Excessive dryness (throat, skin, eyes etc.)
Degenerative disease	Inflammatory disease
Pale tongue, white coat	Red tongue, yellow coat
Empty pulse	Full pulse

In Practice:

Although Yin-Yang essential foundation for understanding symptoms and signs, the above list of signs is too general. We need to distinguish further to get exact diagnosis. i.e., which Organ is involved, which pathogen involved, which channel involved.

Structure and Function
Without structure, function could not occur. Without function, structure would be meaningless.

Mutual Consumption of Yin and Yang
Balance of Yin & Yang is constantly changing. Yin & Yang mutually consume each other.

Four different situations:

1) Excess of Yin	2) Excess of Yang
3) Deficiency of Yin	4) Deficiency of Yang

Excess of Yin: i.e., when excess Cold in the body consumes the Yang (heat). This is an Excess Cold (Full Cold) condition.

Excess of Yang: i.e., when excess Heat (from Exterior or Interior of body) consumes Body Fluids, leading to Dryness or even Heat. This is an Excess Heat (Full Heat) condition.

Deficiency of Yin (Consumption of Yin): i.e., when the body’s Yin energy is depleted, an apparent excess of Yang results, leading to feelings of “empty heat” (mild but very specific heat symptoms, i.e., flushed cheeks, afternoon fever, sweating at night, heat in extremities. This is Deficiency Heat (Empty Heat) condition (i.e., a condition of deficiency and heat), also called “False Fire”.

Deficiency of Yang (Consumption of Yang). When body’s Yang energy is spontaneously deficient – an apparent excess of Yin results, leading to various symptoms involving cold and hypo-activity Deficiency of Yang can also occur after an Excess Cold condition has damaged Yang. This is an Deficiency Cold (Empty Cold) condition (i.e., a condition of deficiency and cold).

Excess of Yin (Full Cold)	Excess of Yang (Full Heat)
Excess of Yin is primary aspect	Excess of Yang is primary aspect
Yin is in true excess	Can eventually cause deficiency of Yin
Can eventually cause deficiency of Yang
Deficiency of Yang (Consumption of Yang)	Deficiency of Yin (Consumption of Yin)
(Empty Cold)	(Empty Heat of “False Fire”)
Decrease of Yang energy is primary aspect	Deficiency of Yin is primary aspect
Yin only apparently in excess	Yang only apparently in excess