本文根据《素问·至真要大论》关于经络间的内在实质联系的论述总结出十二经络阴阳二气盛衰和经脉交接的规律

认为经络阴气变阳气在于手

阳气变阴气在于足

故十二经中经络阴气始于足

汇于胸

上散于手 ;经络阳气始于手

汇于首 (头 )

下泻于足。阴阳二气交换转变形成大周天。In the present paper

the author makes a summary on the regularities of the prosperity and decline

handing over and taking over of yin qi and yang qi of the twelve regular meridians in accordance with the theory of traditional Chinese medicine. The head and the chest are the places where the twelve regular meridians hand over and take over. The location where the meridian yin qi transforms into yang qi is at the hand

and the yang qi transforming into yin qi is situated at the foot. The hand is located in the upper part of the body and belongs to yang and to heaven

while the foot is located in the lower portion and belongs to yin and to earth. Therefore

the yin qi of the twelve regular meridians originates from the foot

flows together in the chest and runs upward to spread to the hand. The yang qi of the twelve regular meridians starts from the hand

converges in the head and goes downward to distribute in the foot. Such handing over and taking over (transformation) and coursing of the yin qi and yang qi of the twelve regular meridians form the "Da Zhou Tian" (big circle

大周天). In clinic

the regulative effects of the acupoints at the hand and foot on the three yin and three yang meridians

those of the acupoints at the head on the six yang meridians

and those of acupoints at the chest on the six yin meridians are of a certain significance.