Two French physicians have done a series of research experiments that make visible the acupuncture meridian system. Jean-Claude Darras, M.D. and Professor Pierre de Vernejoul, M.D. injected radioactive isotopes into the acupuncture points of human patients and traced isotope uptake by gamma-camera imaging. Their experiments found that the isotopes migrated 30 centimeters along the classical Chinese meridian system pathways during the course of 4 to 6 minutes. In contrast, injecting the isotopes into points at random on the body produced no such results. Further tests demonstrated that the migration was not through the vascular or lymphatic system.