Objectives : Extra Meridians are important conception for the proper comprehension of the defensive Gi & the defensive Gi, and the principle of the Gi (氣)‘s flow or diffusion. Methods : Extra Meridians could be explained by an anatomical feature and a functional stage. We should analyze the principle of samhap (三合) to have application to meridians. The study of the relationship between Extra Meridians and regular meridians (12正經) is useful to understand origination of the defensive Gi & the nutritive Gi. Results : The origination of the nutritive Gi & the defensive Gi could be interpreted by the principle of samhap correctly. The energic patterns in the flow of Gi (氣) are changed by cooperation with Extra Meridians and regular meridians (12正經). Conclusions : We could inferred that growth, disease, health, etc are controlled in cooperation with Extra Meridians (寄經脈) and the nutritive Gi & the defensive Gi (營衛). Extra Meridians take many parts in origination of the nutritive Gi & the defensive Gi, in the flow or diffusion of them but various energies are controlled basically by regular meridians (12正經). The defensive Gi is originated by Penetration Vessel (衝脈)) and it seems to be made by the principle of samhap (三合) in the process of the nutritive Gi flow (瀯氣流注).