Abstract
1. The distribution of isotope following a single injection of either Ca45 or C14-proline has been studied in young rats in which one tibia had previously been removed, killed and reimplanted.
2. The dead tibia took up about 25 per cent as much Ca45 or C14 as did the living tibia and the possible processes by which this occurred are discussed.
3. Determination of the "accretion rate " by kinetic analysis of the Ca45 data showed that this was much too high unless the physico-chemical process of uptake of isotope by bone was taken into account.
4. Under the conditions of the experiment it was not possible to estimate the rate of bone matrix formation using C14-proline as a tracer.