Foundations of Traditional Chinese Medicine (TCM) — Exterior Patterns (Biao Zheng), Interior Patterns (Li Zheng) and Their Relationship
Exterior and interior are a pair of concepts used to differentiate the location and severity of diseases. This is a relative concept. In terms of the body structure and internal organs, the body surface is considered exterior, while the internal organs are considered interior; in terms of the organs and bowels, the bowels are exterior, and the organs are interior; in terms of meridians and organs, the meridians are exterior, and the organs are interior, and so on. From the perspective of disease severity, for exterior pathogenic diseases, the pathogenic factor penetrates one layer into the interior, indicating a deeper disease; when it exits the exterior, it indicates a lighter disease. Understanding this relative concept is particularly important in the differentiation of the six meridians and the differentiation of defensive qi (Wei Qi), nutritive qi (Ying Qi), and blood (Xue). This is the broad concept of exterior and interior. The narrow concept refers to the skin, muscles, and meridians as exterior, where these areas are affected by pathogens, belonging to exterior patterns; while the internal organs, qi, blood, and bone marrow are considered interior, where diseases occur, collectively referred to as interior patterns. The differentiation of exterior and interior patterns is significant in the diagnosis of exterior pathogenic diseases. It allows for the assessment of the severity of the disease, clarifies the depth of the pathological changes, and predicts the trend of pathological changes. Exterior patterns are characterized by being superficial and light, while interior patterns are deep and severe. When exterior pathogens penetrate into the interior, it indicates disease progression; when interior pathogens exit to the exterior, it indicates disease regression. Understanding the severity and progression of the disease allows for grasping the evolution of the disease and taking appropriate treatment measures. Exterior patterns refer to the symptoms arising when the six excesses (Liu Yin) and epidemic pathogens invade the body through the skin and mucous membranes. They are commonly seen in the early stages of exterior pathogenic diseases, generally presenting with sudden onset and a short course. Exterior patterns have two distinct characteristics. First, they are caused by the invasion of pathogenic qi. Second, the disease is mild. The location of exterior patterns is in the skin, muscles, and meridians, making them easier to treat. Clinical manifestations: chills, fever, body aches, thin white tongue coating, floating pulse, along with symptoms such as nasal congestion, runny nose, cough, sneezing, and sore throat.
Pathological analysis: Due to the six excesses invading the muscle surface, they obstruct the normal dissemination of defensive qi, leading to heat. When defensive qi is obstructed, it loses its function of warming and nourishing the muscle surface, resulting in chills. The stagnation of pathogenic qi in the meridians causes poor circulation of qi and blood, leading to body aches. The lungs govern the skin and hair, and the nose is the orifice of the lungs; when pathogenic qi enters through the skin and nose, it affects the lungs, causing lung qi to fail to disperse, resulting in nasal congestion, runny nose, and cough. Symptoms such as sneezing and sore throat often accompany these. Since the pathogenic qi is still in the exterior and has not harmed the interior, the tongue coating may show no changes, remaining primarily thin and white. The righteous qi rises to resist the pathogenic qi, hence the pulse is floating.
Interior patterns are a type of syndrome where the disease is deep within the interior (organs, qi, blood, bone marrow). This is in contrast to exterior patterns. They are often seen in the middle or later stages of exterior pathogenic diseases or in internal injuries. The causes of interior patterns can generally be categorized into three situations: first, the transmission of exterior pathogens into the interior, invading the organs; second, direct invasion of the organs by external pathogens; third, emotional disturbances, irregular diet, and excessive work and rest leading to damage to the organs, causing dysfunction and resulting in disease. The scope of interior patterns is vast; aside from exterior patterns, other diseases can be classified as interior patterns. The characteristics of interior patterns can also be summarized in two points: first, the disease location is deep; second, the condition of interior patterns is generally more severe.
Clinical manifestations: The causes of interior patterns are complex, with a wide range of locations and numerous symptoms, often appearing in forms of either cold or heat, or deficiency or excess, thus detailed content can be found in each chapter of differentiation. Here are a few common symptom and pulse analyses: high fever with aversion to heat or slight fever with tidal heat, irritability and confusion, thirst with a desire to drink, or aversion to cold with cold limbs, fatigue and weakness, and a pale tongue with excessive saliva. Constipation, short and red urine, or loose stools, clear and long urine, abdominal pain and vomiting, thick tongue coating and deep pulse.
Syndrome analysis: The above-listed symptoms are merely some common symptoms and pulses that may appear in various interior patterns of cold, heat, deficiency, and excess. In terms of heat and cold, interior patterns can be either heat without cold or cold without heat; heat can manifest as high fever or aversion to heat. Slight fever and tidal heat are often seen in internal injuries with yin deficiency and empty fire rising. Cold symptoms manifest as aversion to cold, which can be alleviated by covering with clothing, resulting from insufficient yang qi or internal invasion of cold, damaging yang qi, leading to cold. Irritability and confusion are manifestations of excess heat disturbing the mind; thirst with a desire to drink and short red urine are due to excess heat consuming body fluids. Constipation occurs due to heat binding in the intestines, leading to depletion of fluids and loss of normal function. Those with insufficient yang qi often exhibit fatigue and weakness, while those with deficiency of cold may show a pale tongue with excessive saliva, and spleen deficiency may lead to loose stools. Abdominal symptoms, which are associated with the organs, include abdominal pain, vomiting, constipation, loose stools, short red urine, or clear long urine, all of which are signs of interior disease. Thick tongue coating and deep pulse are signs of disease being internal. When exterior pathogens penetrate into the interior, it has not yet entered the interior; or when interior pathogens surface, it has not yet reached the exterior, the conflict between the pathogenic and righteous qi at the interface of exterior and interior is termed half exterior and half interior patterns. This presents as alternating chills and fever, fullness in the chest and flanks, irritability with a preference for vomiting, lack of desire to eat or drink, bitter mouth, dry throat, dizziness, and wiry pulse. This understanding of half exterior and half interior patterns is fundamentally similar to the differentiation of the lesser yang disease in the six meridians. The differentiation between exterior patterns and interior patterns primarily involves examining changes in cold and heat, tongue appearance, and pulse characteristics. Generally speaking, in exterior pathogenic diseases, the simultaneous presence of fever and aversion to cold indicates exterior patterns, while heat without cold or cold without heat indicates interior patterns. The tongue coating in exterior patterns does not change, while in interior patterns, the tongue coating often shows changes; a floating pulse indicates exterior patterns, while a deep pulse indicates interior patterns. The skin and internal organs of the human body are interconnected through the meridians. During the progression of a disease, under certain conditions, there can be a mixture and transformation of exterior and interior patterns, such as simultaneous occurrence of exterior and interior diseases, exterior pathogens entering the interior, and interior pathogens exiting to the exterior.