J. M. GARVAN, E. P. GEORGE, F. A. ROCKE, AND S. VINCE 



uptake in liver, bone marrow and spleen at various levels of specific dose. It 

 should be noted that the instrumental errors involved in the individual 

 assay figures which make up the means are negligible compared with the 

 standard deviations quoted. 



We have used as a measure of the concentration of ^^^Au in a given tissue 

 the ratio of the specific activity in the tissue to the specific dose administered. 

 This ratio is referred to as the 'concentration' and is measured in [j.C/g 

 tissue per mC/kg whole-body. It will be clear that the value of the concen- 

 tration in a given tissue is the ratio of the specific activity in that tissue to the 

 average specific activity over the whole body, and that the average concen- 

 tration must always be unity over the whole body, regardless of the specific 

 dose administered. 



Table 2 shows the range, mean and standard deviation of the concentration 

 for rabbits which died after receiving specific doses of 2 • 5 to 3-0 mC/kg. 



Table 2. Concentration of ^''^Au in liver, bone marrow and spleen 



The assay findings regarding relative concentration between rabbits were 

 confirmed by microscopic examination of tissue slides for the presence of 

 gold aggregates. 



No concentration comparable in value with those shown for liver, bone 

 marrow and spleen was observed in any other tissue. 



Except in the cases of two rabbits, assay specimens of liver were made up 

 by pooling several small pieces of mass of the order of 0-2 g. In the two 

 cases mentioned, separate assays were made of pieces of mass of the order of 

 1 g from different parts of the liver. The observed standard deviations 

 of the specific activity over these two sets were +0-5 per cent and +8-0 

 per cent of the mean values. 



Except in the cases of three rabbits, assay specimens of bone marrow were 

 obtained from the shaft of one femur only and were of mass of the order of 

 0-5 g. Table 3 shows, for the three exceptions mentioned, the sites of origin 

 of multiple specimens and the corresponding concentrations of ^^^Au. 



Roentgen doses 



Roentgen doses in REP to tissues due to /3 radiation have been computed 

 from specific activity of ^^^Au, using the formula of Mayneord^, and on 

 the assumption that the tissue dimensions are large compared to the range of 

 j3-particles, which is of the order of 1 mm. Doses due to y radiation might 

 be roughly estimated as of the order of 20 per cent of the corresponding 



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