In roentgen-ray therapy the interest in recent years has been directed almost entirely toward influencing the deeply lying organs. To a certain extent, this may explain why other branches were neglected, so that, for instance, the subject of superficial roentgen-ray therapy was considered more or less closed. In the last few years, interest has been focused more on the biologic problems than on the physical, which could be foreseen. One of the later questions is the fundamental point as to whether there is a different biologic action with different wave lengths, and this basic problem has to be considered as unsolved up to now, in spite of the fact that at present the majority of authors incline to the opinion that the biologic effect depends only on the absorbed ray energy.
But in discussing the topic under consideration, this problem is relatively unimportant. My Grenz-ray1 method, however, should be