One-week-old rats were killed at time intervals ranging from eighteen hours to fifty-four days after the administration of radio-active phosphorus. The specific activities of radio-active phosphorus were determined for various parts of the skeleton.
It was found that during these fifty-four days no equilibrium was reached as regards the distribution of radio-active phosphorus in the skeleton. It was further found that the redistribution of radio-active phosphorus in the skeleton varies with skeletal growth.
In the discussion of the importance of these findings, the following conclusions were drawn:
1. The redistribution of bone salt in different parts of the skeleton varies with the rate of growth of these parts.
2. Compared to skeletal growth, ionic exchange and recrystallization are of minor importance in this redistribution.
3. Parts of the skeleton which differ in rate of growth can thus never reach equilibrium with respect to the distribution of radio-active phosphorus or radio-active calcium after administration of these isotopes.