《黄帝内经·素问·调经论》
黄帝说：医经上所说的阳虚则生外寒，阴虚则生内热，阳盛则生外热，阴盛则生内寒。我已听说过了，但不知是什么原因产生的。
帝曰：经言阳虚则外寒，阴虚则内热；阳盛则外热，阴盛则内寒，余已闻之矣，不知其所由然也。
The Yellow Emperor said: I have heard what medical books say that when Yang is deficient, there will be external cold; when Yin is deficient, there will be internal heat; when Yang is excessive, there will be external heat; when Yin is excessive, there will be internal cold. But I don't know the reasons.