《黄帝内经·灵枢·官能》
邪气伤害了人体，便会出现恶寒战栗，形体振动的症状；正邪伤害人体，先只是在气色上稍微有一些变化，身体上并没有什么特殊感觉，此时邪气似有似无，若存若亡，症状也不明显，病人的确切病情也不易知道。
邪气之中人也，洒淅动形；正邪之中人也，微先见于色，不知于其身，若有若无，若亡若存，有形无形，莫知其情。
When the evil qi damages the human body, the symptoms of chills and shivering and body vibration will appear. When the evil and righteous qi damage the human body, they will only cause slight changes in the complexion at first. The body will not have any special feelings. At this time, the evil qi seems to exist and not exist, to live and not to live. The symptoms are not obvious, and the patient's exact condition is not easy to know.