388 



ADVENTURES IX RADIOISOTOPE RESEARCH 



Table 3. — Frog I, Kept at 2°, Killed after 12 Days 

 Ash weight: 3.235 gm 



1 mgm bone P had the same chance to be replaced by labelled P as 

 1 mgm muscle P. 1 gm bone tissue contains about 30 times as much 

 P as 1 gm muscle tissue. The comparatively low activity of the ])one P 

 is due to the fact that those phosphorus ions which are located on the 



Table 4. — Frog II, Kept at 2°, Killed after 12 Days 

 Ash weight: 3.014 gm 



Weiglit of fash tissue 



Weight iif ash 



Per cent of labelled 

 P administered found 

 in 1 gm fresh tissue 



Right femur 

 Left femur . 

 Right tibia . 

 Left tibia . . 



Right thigh . 

 Left thigh . . 

 Right calf . . 

 Left calf . . . 



gm 



5.461 

 4.635 

 1.670 

 1.679 



0.24 

 0.23 

 0.28 

 0.31 



surface of the apatite crystallites containing the mineral constituents 

 of the bone can be replaced by a physical exchange process with the 

 labelled phosphate in the plasma or the lymph, while the phosphate 

 ions present inside these crystals cannot be replaced. Labelled phosphate 

 ions can only be incorporalerl into the inside of the apatite crystalHtes 



