6 dbaa toe Oeallbls Bld Local alle le 52 100 PLASMA 10 e \ e Ee > =om} 2 "HOT SPOT" i oR a WO € O Tl . A a QoQ \. ms 2 10 ay a WHOLE BONE oc oO = w 8 Al DIFFUSE A 0-1 1 5 DAYS. 10 50 100 Fig. 46—Diminution of Ca in rabbit vertebrae At long times, however, the high level Ra dogs con- tinued to show the samedifference, while the Ca rabbits showed a much higher loss of diffuse label from the vertebra than from the tibia, in parallel with the loss in activity from the individual bone, not from the skeleton as a whole. In the human radium cases, the quantitative auto- radiographie data on bones other than the cortex of the long bones, is insufficient to draw any conclusions re- garding any difference in either the diffuse or ho activity between different bones or the pattern 01 with time. A study along these lines is in progre our laboratory. However,since the concentration 11 cortex of the tibia bears a much more constant rat the average skeletal concentrations than any « bone studied (Figure 42), the use of the diffuse in this site as an index for total skeletal retention. 1 appear to be a good choice.