Originally published in Minerva Nucleare 1, 182 (1957), 

 Lecture delivered in 1956 at the international meeting of miclear medicine in Turin. 



100. HISTORICAL PROGRESS OF THE ISOTOPIC 



METHODOLOGY AND ITS INFLUENCES ON 



THE BIOLOGICAL SCIENCES 



G. Hevesy 



By adding a radioactive isotope to atoms or molecules we can label 

 these and follow their path. That the labelling device was bound to find 

 a very extended field of application was clear already in 1913 when it 

 was first apphed. With increasing time and increasing availability of 

 radioactive isotopes the field of application of radioactive indicators 

 immensely widened and is to be expected to expand further in the years 

 to come. 



For the first decade, radioactive indicators found application in the 

 realm of inorganic and physical chemistry only. But the introduction 

 of some of the leading principles applied in the later biological studies 

 goes back to these early times. The method of isotope dilution, for 

 example, which finds such an extended application in biochemical, 

 physiological and clinical studies goes back to these early days. The 

 first application of radioactive indicators in plant and animal physi- 

 ology was carried out in 1923. Both the uptake of with ThB or RaD 

 labelled lead by bean seedlings and its release by the plant when 

 placing it in a culture solution containing non-radioactive lead was 

 studied. This was soon followed by the study of the uptake of labelled 

 atoms by the animal organism. 



In the investigations carried out up to 1933 only the isotopes of lead, 

 bismuth, thallium, radium, thorium and actinium were applied as tracers, 

 thus isotopes of a very restricted number of elements and none of them 

 a main constituent of the living organism. But lead isotopes as tracers 

 found even in the recent times new useful applications in physiological 

 and clinical studies. The lead isotope ThB proved to be a useful label of 

 red corpuscles and RaD found application in the study of the conserva- 

 tion of lead by the all-through-labelled skeleton of mice obtained by 

 administering to the mother RaD and also to the offsprings until adult 

 age was reached. 



In 1932 and 1933 most fundamental discoveries were made Mhich were 

 bound to deeply impress the very few workers who at 1 hat date were 

 interested in the application of isotopic tracers. These discoveries were 



