96 APPLIED RADIOACTIVITY 



wood of the plant rather than in the bark. They also found a moder- 

 ately rapid radial transfer from the wood to the bark. 



The considerable interest in the metabolism of calcium has been 

 stimulated because radiocalcium (half-life 180 days) has become avail- 

 able for studying this metabolic problem in bone, which is composed 

 largely of calcium in the form of tricalcium phosphate. 



Radioactive tracers provide a unique method for investigating a 

 normal animal or plant under equilibrium conditions. Many problems 

 in physiology and biochemistry are being re-examined with the aid of 

 radioactive tracers. The new results will probably provide valid evi- 

 dence for discarding many alternative or conflicting interpretations of 

 old observations. 



Radium Injuries and Radium Poisoning 



The earliest recorded radium injury was acquired by Becquerel, who, 

 in carrying a tube of radium salt in his vest pocket for several hours, 

 discovered several weeks later that he had developed a " radium burn," 

 an inflammation in that part of the skin located underneath the pocket 

 in which he had carried the radium salt. Curie then repeated the experi- 

 ment on his own person and conclusively proved that the radiation was 

 capable of effecting an inflammatory reaction in normal skin. Besnier 

 was probably the first to suggest the use of radium as a therapeutic 

 agent because of his familiarity with the results of roentgentherapy. 



Injury from radium may take place when a radioactive substance 

 enters the blood stream by ingestion or injection. Modes of entrance 

 of radium into the human body include breathing of radioactive gas, 

 drinking of radium water nostrums, and intravenous and other injec- 

 tions of radium salts. Technicians, chemists, and miners handling 

 radioactive materials are often injured by the radiations . and can be 

 poisoned by taking the material by mouth. 



As is generally true in any heavy-element poisoning, some radium 

 salts are deposited in the bony tissues. A small fraction of the total 

 amount of radium taken into the body becomes relatively fixed in the 

 bones, the fixation being considerably higher after intravenous injection 

 than after ingestion of radium. Retention is diminished by acidosis 

 while on low-calcium diet, as this tends to increase the rate of elimination 

 of calcium and heavy elements from the body. 



If radium is taken by mouth or by injection, a fraction of it remains 

 permanently in the body. According to the individual, from 2 to 35 per 

 cent of the radium received by mouth remains in the system more than 

 5 days after ingestion, and 55 to 65 per cent received by intravenous 

 injection remains more than 5 days. By the tenth day after taking 



