30 ADVENTURES IN RADIOISOTOPE RESEARCH 



been fully corroborated by work carried out in our laboratory, and 

 especially by the beautiful work carried out in Oxford by Lajtha and his 

 associates. 



When we started with Paneth in the first days of 1913 to apply radium 

 D as a tracer of lead, the word "isotope" was not yet coined. Groups of 

 radioactive substances such as mesothorium and radium, or ionium and 

 thorium, w^ere denoted by Soddy as "chemically inseparable elements". 

 Much has happened since those days! 



