《黄帝内经·素问·阴阳应象大论》
北方应冬，冬天生寒，寒气与水气相应，水气能产生咸味，咸味能滋养肾气，肾气能滋长骨髓，骨髓充实，则又能养肝，肾气关联于耳。
北方生寒，寒生水，水生咸，咸生肾，肾生骨髓，髓生肝，肾主耳。
The northern element corresponds to winter; winter produces cold; cold qi corresponds to water qi; water qi produces salty flavors; salty flavors nourish kidney qi; kidney qi gives rise to bone marrow; full bone marrow nourishes the liver; kidney qi is related to the ears.