The channel syndrome and the fu-organ syndrome are further classifications of symptoms and signs of a particular channel in the six-meridian pattern identification. The channels are internally connected to the zang-fu organs. When pathogenic factors invade the qi of the channels and have not yet accumulated in the fu organs, the symptoms are referred to as "channel syndrome"; if they accumulate in the fu organs, it is called "fu-organ syndrome." Clinically, channel syndrome and fu-organ syndrome generally refer to diseases of the three yang channels. The division of channel syndrome and fu-organ syndrome was established by later commentators (on cold-damage disease). For example, in Taiyang disease, symptoms such as aversion to cold, headache, and fever; in Yangming disease, symptoms such as high fever, thirst, and spontaneous sweating; and in Shaoyang disease, symptoms such as alternating chills and fever, and restlessness in the chest are referred to as "channel syndrome."