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The Renying pulse (Renying, Human Welcome), located one fen anterior to the Guan position on the left hand, is used to observe injuries caused by external pathogens such as cold, summerheat, dryness, dampness, wind, and heat. These pathogens all enter through the collaterals and are received/nurtured there, hence the name Renying. Ancient medical theories state that the Taiyang (Greater Yang) channel governs the Qi of all Yang channels, and generally, when affected by external pathogens, it begins with Taiyang. However, upon examining the original meaning of the classics, this view seems not entirely correct. Wind tends to injure the Liver; Cold tends to injure the Kidney; Summerheat tends to injure the Pericardium; Dampness tends to injure the Spleen; Heat tends to injure the Heart; Dryness tends to injure the Lung. Since Summerheat and Heat belong to the same Qi, and Dryness and Dampness share the same origin, they are not discussed separately. By analogy, Wind should enter via Shaoyang (Lesser Yang); Dampness should enter via Yangming (Bright Yang); Summerheat should enter via the Sanjiao (Triple Burner); whereas Cold enters via Taiyang. Thus, the *Classic* states: "Yin serves as the master, Yang provides the rectification; distinguishing from Yang allows one to know the origin of the disease." This refers to this principle.

For Taiyang injury by Cold, the primary manifestation is a floating, tight, and vigorous pulse at both the Chi position of the left hand and the Renying pulse. Floating indicates the Foot-Taiyang channel; Tight indicates Cold injury; Vigorous indicates disease progression. Symptoms include stiffness and pain in the head and neck, pain in the lower back and spine, absence of sweating, aversion to cold, but no aversion to wind.

Yangming injury by Dampness presents with a choppy, fine, and long pulse at the Guan position of the right hand and the Renying pulse. Choppy indicates the Foot-Yangming channel; Fine indicates Dampness injury; Long indicates disease invasion. Symptoms include joint pain, heavy bi-syndrome (painful obstruction) with weakness, scanty or difficult urination, and undigested food in stool (sun-xie).

Shaoyang injury by Wind presents with a wiry, floating, and scattered pulse at the Guan position of the left hand and the Renying pulse. Wiry indicates the Foot-Shaoyang channel; Floating indicates Wind injury; Scattered indicates the arrival of disease. Symptoms include feverish body, aversion to wind, spontaneous sweating, neck stiffness, and fullness/tightness of the sinews.

Hand-Shaoyang injury by Summerheat presents with a surging, empty, and rapid pulse at the Chi position of the right hand and the Renying pulse. Surging indicates the Hand-Shaoyang channel; Empty indicates Summerheat injury; Rapid indicates disease increase. Symptoms include feverish body, aversion to cold, headache, symptoms resembling Cold injury, irritability, and thirst.

Foot-Taiyin injury by Dampness presents with a soggy, fine, and deep pulse at the Guan position of the right hand and the Renying pulse. Soggy indicates the Foot-Taiyin channel; Fine indicates Dampness; Deep indicates disease adherence/stagnation. Symptoms include heavy body, weak legs, vexing joint pain, cold bi-syndrome, and distension/fullness.

Foot-Shaoyin injury by Cold presents with a deep, tight, and rapid pulse at the Chi position of the left hand and the Renying pulse. Deep indicates the Foot-Shaoyin channel; Tight indicates Cold; Rapid indicates disease transmission. Symptoms include dry mouth and tongue with thirst, aversion to cold in the back, yet paradoxical fever and fatigue.

Foot-Jueyin injury by Wind presents with a wiry, weak, and urgent pulse at the Guan position of the left hand and the Renying pulse. Wiry indicates the Jueyin channel; Weak indicates Wind; Urgent indicates pathological change. Symptoms include spontaneous sweating, aversion to wind, fatigue, and acute pain in the lower abdomen.

Hand-Jueyin Pericardium injury by Summerheat presents with a deep, weak, and slow pulse at the Chi position of the right hand and the Renying pulse. Deep indicates the Pericardium channel; Weak indicates Summerheat injury; Slow indicates disease-induced fatigue. Symptoms include alternating chills and fever, resembling malaria, irritability, thirst, dizziness, coldness in the back, and greasy complexion.

These describe the distribution across the Six Channels regarding external pathogen injuries. Excluding Dryness-Heat, these four climatic factors (Wind, Cold, Summerheat, Dampness) are narrated as the main framework. If transmission occurs, treatment should follow the specific injuries described in the separate discussions of the Six Channels, addressing symptoms according to the channel involved. If Dryness-Heat injures the Heart and Lungs, treatment should also follow classical principles for regulation. If the four climatic factors combine and the Six Channels intersect, one must carefully examine the pulse and symptoms to distinguish clearly, treating either first or later, combined or separately, whether in the collaterals or channels, exterior or interior. The movements of the four seasons correspond to the pulse; climatic conditions vary with time and naturally align with pulse periods. The subtlety lies in the pulse, which must not be neglected; examination has its discipline, starting from Yin and Yang; initiation has its channels, generated from Yin and Yang. This is what is meant.