Why can Gegen decoction treat three syndromes: strong neck, vomiting and benefit? What's the difference between Guizhi and Gegen Decoction?

It's Treatise on Febrile Diseases 3 1 cloud: "Sun disease, strength (? ), those who have no sweat and evil wind, pueraria decoction is the main one. " It can be seen that the strength of Gegen decoction syndrome is caused by exogenous cold evil, sun invasion, unfavorable menstruation and qi, and muscle and vein dystrophy. Radix Puerariae decoction is prepared from Guizhi decoction, Radix Puerariae and Herba Ephedrae. It has the functions of relieving muscle sweating, promoting fluid production and relaxing muscles and tendons, so it can treat neck and back. Pueraria lobata is used in the prescription, which is sweet and pungent in nature, can produce fluid, moisten tendons and dredge veins, relieve exterior symptoms and eliminate pathogens. Its syndrome is exterior but not sweating, so Guizhi Decoction plus Ephedra can not only reconcile camp and health, but also perspire and eliminate evil. However, there is no need to sweat a lot because of tendon dystrophy, so Paeonia lactiflora converges and nourishes yin, and ginger, jujube and licorice benefit the middle energizer and help the stomach. There are thirty-two clouds in Treatise on Febrile Diseases: "Those who suffer from diseases of the sun and Yangming will benefit their health, and Gegen decoction will treat them." 33 cloud: Sun and Yangming are combined with diseases, which are useless, while those who vomit are mainly Pueraria lobata and Banxia Decoction. "These two articles are forced by Sun's contempt for evil.