28 FREDM. UBER 



based on makeshift or arbitrary units. As an example, the earher 

 investigators of the biological effects of X radiation could not measui-e 

 the radiation dose in unique fundamental terms but had to resort to 

 lengthy statements of conditions whose value in turn depended on the 

 particular commercial brand of X-ray tube employed. This un- 

 satisfactory procedure persisted for mamy years, although it was clear 

 that the available information was insufficient to permit an accurate 

 quantitative analysis of the data or to enable other workers to du- 

 plicate the experiments. Quantitative progress was thus curtailed 

 until a standard unit of measurement was adopted. For current re- 

 search to be published in this field without relating the measurements 

 in a knowTi way to the roentgen unit, however, would appear to be 

 inexcusable. Considering the great amount of time and effort de- 

 voted to the conduct of a scientific investigation , it is certainly foolish 

 not to take the additional steps that may be necessary in order to 

 record the measurements in a reproducible unit known or available to 

 all. Another pertinent illustration is the measurement of a liquid dose 

 or ration in terms of drops. Although rather accurately reproducible 

 by the original investigator, it becomes quite hopeless for others to 

 duplicate measurements satisfactorily unless they are specified also in 

 some absolute unit. 



Many investigations of a biophysical nature require the use of one 

 or more physical or chemical constants for the computation of the 

 data. Therefore, it should be realized that the accepted values of 

 these "constants" are subject to change. The atomic weights of the 

 elements are revised almost annually and other fundamental quan- 

 tities likewise must be periodically subjected to review. The ac- 

 cepted value of the electronic charge, for example, has changed by 

 nearly three-fourths of one per cent during the past twenty years. 

 Thus the data and computations of numerous studies which have been 

 based on the older values, should be altered by a similar amount. An 

 investigator not only must be alert to the best values of the moment 

 for a given constant but also must consider how the revised values 

 will influence the results of earlier investigations of similar problems 

 with which he may wish to make comparisons. 



Since present experimental research is very heavily indebted to 

 the existing scientific foundations built by others, it is obligatory on 

 all to make available the results of their work in an intelligible form. 

 Among other things, this demands a statement of the numerical values 

 of the physical constants that have entered into the calculations. 



