Deep-seated cold lurking within the body may be triggered by a recent contraction of wind-cold; it may also be triggered by the rising of seasonal yang in spring; or it may be triggered by improper diet and overexertion. The external manifestations of cases triggered by recent wind-cold contraction are similar to those of Shanghan (Cold Damage), but differ in that: when the Upper Jiao is affected by Shanghan pathogen, there is aversion to cold and fever, stiffness and pain throughout the meridians and collaterals of the body, most severe in the head and neck; the pulse is deep, tight, and rapid; respiration is slightly accelerated but not coarse; the patient often desires to lie supine with limbs extended.

In cases triggered by latent cold, although fever has already appeared, the heart often feels piercingly cold; the bones, muscles, and joints ache and distend, most severely below the thighs, specifically at the knees and shins; the pulse is floating, wiry, and large, but becomes smaller upon heavy pressure, with a trembling sensation against the fingers during its rise and fall; respiration is panting and coarse; the body is hot while the feet are cold; although the chest is irritable, the feet constantly desire to curl up and cannot extend.

Cases triggered by seasonal yang, improper diet, and overexertion present externally similarly to Dongwen (Winter Warmth) and Chunwen (Spring Warmth), but differ in that: Shiwarm presents with high fever and coarse breath; prolonged palpation of the skin reveals burning heat; the pulse is surging, slow, and rapid, coming swiftly and departing slowly; the tongue coating is entirely yellow; thirst drives the desire for frozen beverages; nausea occurs intermittently; the bones and muscles feel slightly distended but not painful; mental clarity is impaired; appetite is lost even before chest fullness appears.

Latent cold triggers mild fever; exertion immediately induces panting; alternating chills and fever occur; prolonged palpation of the skin reveals no heat, or even coldness like ice; the pulse is surging, slow, and delayed, lacking vigor on arrival but swift on departure, becoming tight upon deep palpation and at the Chi position posteriorly; the anterior tongue coating is yellow and the posterior is white, indicating exterior yellow and interior white; thirst exists without desire to drink, or desire for hot drinks; Qi rushes from the lower abdomen, causing sudden violent vomiting; bones and muscles ache and distend; mental clarity remains intact; appetite is slightly reduced but hunger arises easily. These are all initial manifestations. At this stage, Qi and Blood have not yet become turbid and chaotic; pathogenic factors and healthy Qi have not yet confused each other. This is the critical juncture for distinguishing between Shanghan, Wenbing (Warm Diseases), and latent cold. If syndrome differentiation is accurate and treatment is administered correctly at this point, recovery can be expected promptly. If this opportunity is missed and treatment is neglected, complications will swarm forth, upper and lower regions influencing each other, exterior and interior attacking each other, resulting in hidden macules and papules, frequent phlegm and cough, oral ulcers and gum erosion, umbilical pain, and diarrhea. The truth and falsehood of cold and heat become difficult to clarify; the depth and superficiality of deficiency and excess become impossible to distinguish. Physicians may panic and act hastily, attending to one aspect while neglecting another, rarely avoiding failure.

Old theories on distinguishing Shanghan and Wenbing state: Wenbing originates from the interior, Shanghan from the exterior; furthermore, Wenbing is differentiated by the Three Jiao, while Shanghan is differentiated by the Six Channels. I add to this: In severe cases of Shanghan, the pathology moves upward from below; in severe cases of Wenbing, the pathology moves downward from above. In fatal cases of Shanghan, the pathology moves downward from above; in fatal cases of Wenbing, the pathology moves upward from below. When Shanghan pathology remains below and does not move upward, it is a mild case; when it remains above and does not move downward, it is the mildest case. When Wenbing pathology remains above and does not move downward, it is a mild case; when it remains below and does not move upward, it lies between mild and severe, uncertain.

Wenbing arising from latent Qi enters through the nose and mouth, lurks in the Diaphragm and Mo Yuan (Membrane Source), and infiltrates the Blood level of the Three Jiao. If it manifests immediately, it spreads via the nose and mouth to the Lung and Stomach, consuming fluids and causing turbidity in the Blood level. Shanghan arising from latent Qi enters through immersion of the lower legs, lurks in the sinews, collaterals, and bone joints, and infiltrates the Qi level of the muscle membranes. If it manifests immediately, it spreads from the Cou Li (Pores) to the Upper Jiao, obstructing Yang Qi and causing agitation in the Qi level.

When latent Shanghan transforms into Wenbing, it is not that cold transforms into warmth, but rather that the individual's constitution possesses abundant Heat in Qi and Blood. Cold lurks below, preventing Yang Qi from descending and communicating. The Three Jiao accumulates stagnant heat, growing day by day and month by month. Upon manifestation, only Heat syndromes of the Three Jiao are seen, with no signs of Cold in the Lower Jiao. Moreover, clearing and draining the Heat in the Upper Jiao naturally aids in expelling the Cold in the Lower Jiao. Therefore, despite symptoms such as thigh and shin distension and pain, predecessors often forcibly attribute these to Wenbing and dare not discuss them as caused by Cold. If the Cold in the Lower Jiao is too severe for the Heat in the Upper Jiao to assist in expulsion, one should wait until the Heat intensity reduces by half, then add medications to treat separately. One must follow the principle in the Neijing (Inner Canon): "When the disease site is distant, utilize the flavor and qi of food to reach it." Otherwise, the removal of Warmth leaves Cold behind, leading to vomiting above and diarrhea below, with obstruction in the Middle Jiao, fitting the description of a person with "partial death and Lower Deficiency." In reality, this is not Lower Deficiency, but rather Lower Cold due to mismanagement.