In the present paper the authors analyze the anatomical structure of the meridian running track by using the dialectical thought and comprehensive analysis of the integrated Chinese and western medicine. It has been observed that the "Qi-passages" of the 14 meridians of Chinese medicine are located in the connective tissue among the interspace of the muscles, etc. distributing longitudinally. The "Qi-passages" of the 15 Luomai (collaterals of the meridians) are located in the connective tissue among the interspace of the muscles, etc. distributing transversally, while those of the small branches of the meridian collaterals are located in the interspace mesenchyme of the muscle bundles distributing in the whole body. The "Qi-passages" of the tiny branches of the meridian collaterals are located in the mesenchyme of the intracellular space, such as the muscle fibers in the whole body. The authors hold that the so-called "Mai Qi" of the meridian-collaterals is the liquid-Qi flowing in the vertical and horizontal tissue interspaces. The "Qi-passage" of the meridian-collaterals of Chinese medicine is the pathway of the liquid-Qi of the tissue interspaces. The structure of the meridian-collaterals is the tissue interspace. The meridian-collateral system is a regulation-control system in the human body where the Qi-passages communicate with each other, and is, in fact, the protoplasm, the liquid-Qi circulating in the tissue interspaces.