If it moves through the skin, it causes itching; if it lingers for a long time without departing, it becomes Bi syndrome (obstruction syndrome). The Wei Qi (Defensive Qi) is thereby prevented from circulating freely, resulting in muscles that are numb and insensible.
When Xu Xie (Empty/False Pathogens) invades only half of the body and penetrates deeply, residing within Ying Qi (Nutritive Qi) and Wei Qi (Defensive Qi), as Ying and Wei Qi gradually decline, the Zhen Qi (True/Essential Qi) departs, leaving only the pathogenic factor to remain alone, leading to Pian Ku (hemiplegia). If the pathogenic factor is shallow, there is pain in the meridians on one side.
This passage discusses the injury caused by pathogens attacking one side: deep invasion results in Pian Ku (hemiplegia) or paralysis of half the body; shallow invasion results in pain in the meridians on one side, because the True Qi has been depleted while the pathogen occupies the space.
When Xu Xie enters the body deeply, Cold and Heat contend with each other. After lingering for a long time, they become fixed internally. If Cold overcomes Heat, it causes bone pain and muscle emaciation; if Heat overcomes Cold, it causes rotting flesh and腐 muscle forming pus, damaging the bones internally, leading to Gu Shi (bone erosion/necrosis). If a disease previously affected the sinews, causing them to contract and unable to extend, and the pathogen remains between them without returning/disappearing, it develops into Jin Liu (sinew lump); if there is an accumulation, Qi converges upon it, Wei Qi (Defensive Qi) stays there, unable to...