THE USE OF STABLE ISOTOPES IN BIOLOGICAL AND MEDICAL

During the past 15 years there has been a rapid and extensive development of the use of isotopes in biological and medical investigation. In 1923, Hevesy's pioneering studies, in which thorium B was used to investigate the absorption and locali-zation of lead by plants, revealed some of the pos-sibilities of the use of tracer technique for bio-chemical research. The exploitation of these pos-sibilities marked time, however, until isotopes of elements more widely associated with biochemical processes were made available. The discovery of deuterium by Urey in 1931 and the development of methods for production of heavy water were the first steps toward providing stable isotopes for tracer studies in biological systems