Scientists hold the most optimistic views concerning the possibilities which lie in the field of x-ray and related ray applications. This is true of workers in fields which are widely separated. H. J. Muller, of the University of Texas, for instance, stated of his field, genetics, that x-rays are means by which we may be able to regulate life itself. His statement has to do with the kinds of modifications which we may make in genes and chromosomes. A. H. Compton is quoted as stating that if the voltage of x-ray tubes can be raised to between ten and twenty million, the door to the release of atomic energy may be opened. It is the purpose of the following list to name the conditions which may be varied in either the tube, the ray, the surrounding spaces, or in the treated material itself during such fundamental investigations of ray effects. An attempt has been made to imagine all of the possible variables of possible significance, but no claim is made, of course, that it is complete. Nevertheless, it is believed that a great deal of the future sciences of genetics, ray chemistry, and ray physics, as well as future x-ray machine design, must be erected within the framework here indicated. At best, however, the aid will be merely such as the armchair philosopher can give the real investigator. The writer would be glad to hear of additions to the list which others may make, and suggests that some scientific librarian take the subject in hand to give the variables library index numbers in the same way that radio literature has been codified. An enormous ray effect literature already exists. The list, proceeding from the obvious variables to the obscure ones, is as follows: Vary the identity of the material rayed. Vary distance from ray source. Vary time of treatment. Vary number of treatments. Vary voltage of tube, i.e., hardness of ray. Vary milliamperage of tube, i.e., quantity of ray. Vary target temperature. Vary target material: (a) metals; (b) non-metals; (c) mixtures or compounds. Vary filament temperature. Vary filament area: Vary filament material. Feed tube alternating current: (a) vary wave shape. Feed tube direct current: (a) vary current, as pulsating. Control electron flow in tube with grid: (a) modulate ejected x-rays. Control character of radiation by magnetic field (Faraday effect). Control character of radiation by electrostatic field. Control character of radiation by filter: (a) liquids; (b) solids; (c) solutions; (d) thickness; (e) angle. Vary character of secondary radiation in subject by first injecting secondary x-ray generating material. Vary character of x-rays by mixing with other radiation, such as radium, ultra-violet, etc., of selected wave length.