The relative efficiency of the local irroration of tumors was tested with a novel approach. The tumor was grown to incorporate 3 thermistors and was supplied by a single artery and vein. The vein was cannulated and the blood flow of the whole tumor was continuously measured while a cold pulse of plasma was injected in the tumor artery. From the changes in temperature measured by the 3 thermistors it was calculated that areas of the tumors can be almost totally deprived of blood for several minutes while most of the blood is passing through another area. The intermittence of blood flow shields regions of the solid tumor from substances with pulse-type concentration in the blood stream.