Experiments on dogs with electromagnetic flow probes implanted around a coronary artery and the ascending aorta indicate that the entry of a person into the experimental chamber can cause a remarkable increase in coronary blood flow. Heart rate usually increases considerably, blood pressure increases only slightly, while aortic blood flow increases at variable times before and after coronary blood flow. It is not yet clear whether these cardiovascular effects are due purely to "effect of person" or to conditioning, with the person as the signal for the momentary coronary occlusion (which the person subsequently accomplishes by manually closing a snare).