402 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946 
Already we have reached the point where a change of decided im- 
portance can be observed. The theoretical and technical means of this 
research are now available. ‘The interest in, and therefore the number 
of articles and books about, subjects in physical medicine, biophysics, 
and medical physics has considerably increased of late. The war has 
stimulated important research in physiology as related to physical 
phenomena. There is much evidence of the desire to make the results 
of recent physical and technological investigations available for the 
service of biology, medicine, or public health. This tendency is mani- 
fested in the fields of electronics and instrumentation, in transporta- 
tion engineering and air conditioning, in nuclear physics and, quite 
significantly, theoretical physics. 
The introduction of physical and technological research into the 
medical field is very promising. Formerly, medicine had been devel- 
cped on a highly empirical basis. Medical men were concerned 
merely with the over-all effects produced; a living organism such as a 
guinea pig would be treated in a specified manner, and the gross 
results of the treatment would be observed. ‘The newer approach in- 
volves a quantitative study of the effects of the various physical phe- 
nomena acting upon the living organism and investigates step by step 
the results of these actions. Even though accurate physical measure- 
ments cannot yet be made on each and every aspect of the phenomena, 
the value of the approach is beyond question. 
To illustrate this type of research, assume that we wish to study the 
medical effect of an X-ray treatment, applied to a given location of a 
tumor at a certain depth in the body. The treatment may be given 
under a great variety of conditions, using different X-ray generators, 
tubes, voltages, currents, filters, and distances between the generator 
and the subject. The biological results of such a treatment will be 
different in each case. But when we know enough about the absorp- 
tion and scattering of X-rays in tissues and the effect of wave lengths 
and other physical magnitudes, we shall be able to predict the dose 
distribution in the body. Experimental results then become com- 
parable, and the biological and medical results can be correlated with 
the physical phenomena causing them. At the same time, the number 
of variables involved diminishes greatly as will the number of opin- 
ions and contradictory reports so frequently encountered in medical 
literature. 
The result of any kind of therapy is to be measured by the clinical 
success and the cure of the disease, of course. The process of healing 
a disease is, however, a consequence of a given treatment in addition 
to a great number of physiological and psychological processes. So 
long as consideration is restricted merely to the treatment and the 
cure, one does not know whether the patient got better because of, or 
