A FUNDAMENTAL essential for any therapeutic prescription is the qualitative and quantitative evaluation of the physical means used and of the reactive effect which takes place from it in certain vital elements. Now, the physical and biologic study of these important problems is quite complete but is still inadequate to establish exact normals of therapeutic technic. Even if the physical definition of the quality and quantity of radiation used can be considered within limits sufficiently exact, the status of the study of their application according to which the energy submitted is transformed in the absorbing media, because the mass of living tissue submitted to radiation is very complex and unhomogeneous. There exists, in fact, in the computation of the factors inherent in the radiobiologic problem a quantity of extremely variable factors, as a result of which it is extremely difficult to establish a valid relationship between the quantity of radiant energy administered, and the reactive effect produced i...