MEDICAL USES OF THE CYCLOTRON — SPEAR 145 



hours. Perhaps the neatest way to manufacture "tagged" sugar, since 

 chemical synthesis of sugar is a difficult process, is by the action of 

 bacteria in reducing carbon dioxide made with radio carbon. 



Radio calcium and radio strontium are taken up selectively by bone, 

 especially in regions where active growth is taking place. Radio 

 strontium, with a half-life of 55 clays, is preferable to radio calcium 

 whose half -life is 180 days and cannot be prepared in the same high 

 concentration as radio strontium. The two elements belong to the 

 same group of the periodic table and have similar chemical and 

 physiological properties. A striking illustration of the deposition 

 of radio strontium in growing bone is shown in plate 3, figure 2. Five 

 hundred millicuries of the element were given to a child 2 days before 

 amputation of the leg for a cancerous growth. An autophotograph 

 of a longitudinal section of the leg, compared with an X-ray photo- 

 graph on the same scale, shows the deposition of the radioactive ele- 

 ment in the tumor cells (malignant growth) and in the epiphysial 

 line (normal bone growth). 



Radio phosphorus is taken up by bone, bone marrow, spleen, lymph 

 nodes, and liver as well as by certain cancerous growths (sarcomata). 

 Its use in the treatment of blood diseases is described in the next 

 section. 



Tracer substances are also being used to study the metabolism of 

 insects and in some interesting studies in comparative morphology. 

 Organs supposed to be homologous in different species can be tested 

 for their uptake of certain radio elements and their activity compared. 

 True homologues deal similarly with a given radio element. 



THERAPEUTIC ADMINISTRATION OF RADIOACTIVE SUBSTANCES 



Since it was known that some substances are selectively absorbed in 

 animals and man, the question arises whether this fact can be used for 

 therapeutic purposes. The idea of intracellular radiation opens up 

 quite a new field of radiation technique. X- or gamma radiation, as 

 normally applied, reaches the cells upon which it is directed by passing 

 through layers of normal cells whose resistance to the radiation consti- 

 tutes a limiting factor in the dosage attainable. The rays also have a 

 constitutional effect known as radiation sickness, which may assume 

 serious proportions. There is now a large range of artificially radio- 

 active substances which are absorbed by cells and emit their energy 

 from within the cell boundary (22<z) . They are all temporarily radio- 

 active with a wide range of radiation energy from soft beta rays to 

 high-energy gamma rays, and they can be administered with far less 

 danger of producing radiation sickness. 



Radio iodine has been used in a few cases of thyroid disease but is 

 unlikely to be of use for malignant growths in the gland. The heavy 



