Among so many etiological factors, it is impossible to discriminate which are responsible for the complications which took place in our experiments. An attempt to explain the occurrence of nephritis, cedema or calcification of the arterial system, for instance, will not be made, but the technique of the operations will be modified in order to suppress as much as possible the causes which may originate these secondary changes. The purpose of this article was not to analyze minutely the physiological or pathological character of the functions of transplanted kidneys, but merely to ascertain whether these functions are efficiently reëstablished. It is to be concluded that an animal which has undergone a double nephrectomy and the grafting of both kidneys from another animal can secrete almost normal urine with his new organs, and live in good health at least for a few weeks. This demonstrates that it is possible to reëstablish efficiently the functions of transplanted kidneys.