146 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 5 



homologue of iodine, known as element 85, was first prepared at Berk- 

 eley and has similar properties. 



The administration of radio strontium is still in the early experi- 

 mental stage. It is selectively absorbed in bone. 



The furthest developments have been made with radio phosphorus 

 which has now been used therapeutically on a relatively large scale. 

 Radio phosphorus, i 5 P 32 , is prepared by the bombardment of red phos- 

 phorus with high-speed deuterons (heavy hydrogen nuclei). In the 

 reaction, the proton is repelled and the neutron captured, so that the 

 stable red phosphorus 15 P 31 becomes the unstable isotope i 5 P 32 which 

 breaks down spontaneously to stable sulfur i 6 S 32 with the emission of a 

 beta ray which can be detected physically. The half-life of radio 

 phosphorus, i. e., the time during which its energy is reduced to one- 

 half by the break-down of its unstable atoms, is 14.3 days. It is usu- 

 ally used as the compound Na 2 HP0 4 , disodium hydrogen phosphate, 

 in a dilution of 15 mg. per cc. or the equivalent of 0.4 millicurie of Ra 

 when freshly prepared. 



Ordinary phosphorus occurs in all living tissues. A phosphorus 

 atom spends, on an average, about 2 months in the body of a rat before 

 it is excreted. But its speed of movement in different organs of the 

 body varies widely. For example in muscle the uptake, "turn-over," 

 and elimination is rapid and the concentration of phosphorus at any 

 given time low. In bone, on the other hand, the turn-over is slow 

 and local concentration high. In growing tissues the uptake is more 

 rapid than in adult. Radio phosphorus is taken up selectively by 

 bone and bone marrow, spleen, lymph, and liver, and by proliferating 

 cells anywhere both normal and malignant. In the case of bone, the 

 rate at which radio phosphorus is deposited in normal, rapidly grow- 

 ing and cancerous tissue is a function of the activity of the enzyme 

 alkaline phosphatase (22 c) . But the results show an individual vari- 

 ation in the actual amount deposited, and a variation for different 

 parts of the same tumor in the case of malignant growths, i. e., when 

 autophotographs are made the fogging of the plates is uneven. 



There are certain human blood diseases characterized by the over- 

 production of blood cells, either the white (leukemia) or the red 

 (polycythemia), and since radio phosphorus is selectively absorbed 

 in the lymphatic tissues and bone marrow where the overproduction 

 occurs, this element has been tried therapeutically in the treatment of 

 these diseases with encouraging results. The uptake of radio phos- 

 phorus in leukemia is greatly in excess of that in a normal healthy 

 animal or person, and in a concentration which reduces, at least tem- 

 porarily, the great excess of white blood cells (fig. 1) . If the trouble is 

 an overproduction of red cells, their reduction is effected by a concen- 



