142 K. SUNDARAM 



of animals in each group is relatively too smaU to warrant statistical evalua- 

 tion. Again the non-uniformity of distribution of ^°Sr in the bone, makes it 

 equally difficult to compute the dose-rate or the total dose received by the 

 cells under consideration. It would be worthwhile to undertake further 

 investigations to validate these conclusions, by determining the type of 

 neoplastic changes in amimals of identical age groups with different levels of 

 skeletal ^^Sr. 



ACKNOWLEDGMENT 



I wish to acknowledge my sincere thanks to Dr. George Casarett, Radia- 

 tion Biology, Atomic Energy Project, University of Rochester, Rochester, 

 N.Y. for makmg available to me the histological material and other facilities 

 for this report, 



REFERENCES 



Casakett, G. W., Tuttle, L. W., and Baxter, R. C. (1961). University of Rochester, 



AEC Document UR-597. 

 FiNKEL, M, P., Bergstrand, B. S., and Biskis, B. 0. (1960). Radiology 74, 458. 



DISCUSSION 



ALEXANDER: Do you think that these conclusions have any significance from the statis- 

 tical point of view? Bj' rough arithmetic you get in 80 rats by fifty weeks two to tliree 

 cases of leukaemia in the whole experiment. Is two to three significantly different from 

 zero? 



gopal-ayengar: Perhaps Dr. Casarett might be able to answer the question of actual 

 number of cases. 



ALEXANDER: Well, the numbers involved must have been so small that none of the figures 

 can be significant. Is there any difference between 0-0017 and 0-0007? 

 CASARETT: As I recall there were between five and ten cases of leukaemias spread 

 between the B and C groups and leukaemia is a very rare disease in rats more so than in 

 man. Our experience is that there is a significant increase in the incidence of rat 

 leukaemia. 



MOLE: One ought to pursue this point because even if there were five to ten cases of 

 leukaemia you still cannot say that there is a bigger incidence in one group or another, 

 because it can stiU occur by chance. 



CASARETT: I am sure that you are correct Dr, Mole in the statistical sense, unless one takes 

 into account the rarity in the larger number of control animals studied in these experi- 

 ments, A, B, C and D are the groups in each of the treated and control groups. For 

 osteogenic sarcoma both in the treated and controls in A and B groups it was 0%, 27-5% 

 in the treated C group with a body burden of 11 ^c and 17-9% in the D group. Skin 

 carcinomas of the face occurred at the same dose level as that which produced an 

 increased incidence of leukaemia — 7-5% in the B group and 11-25% in the C group and 

 none in the A and D groups. The incidence of leukaemia was 0% in both the treated and 



