Experimental setup. 3A- Holder placed on Pericardium meridian and control skin segments. Guide tubes indicate the location of needles on both segments. In this image, needles (a), (b), (c), and (d) are inserted along the control segment. Current is passed between electrodes (a) and (d) and voltage is measured between (b) and (c). 3B- Tissue impedance meter connected to laptop computer and to needle electrodes.