RADIATION DEATH IN MAMMALS 



adrenalectomized animal restored the 3 • 5-day effect. The irradiation of 

 other organs (single and combined : liver, spleen, kidney, intestine) showed 

 a special role for the liver. The irradiation of the splenectomized animals 

 did not result in a change in the 3-5-day effect. Treatment with penicillin 

 and streptomycin also did not influence the 3 • 5-day effect. After in vitro 

 irradiation with high doses, examinations of blood ('prothrombin time') 

 and measurements of tissue respiration were carried out. 



To clarify the 3-5-day effect the irradiation intensity was changed or 

 the dose was fractionated. While change in dose rate showed no effect, a 

 significant difference was found if the same dose was divided in two parts. 



REFERENCES 



1 Rajewsky, B. ' Naturforschung und Medizin in Deutschland 1939-1946 (Fiat- 

 Review of German Science 1939-1946) ' Bd. 21 Biophjsik Teil I. .Dieterich'sche 

 Verlagsbuchhandlung, Wiesbaden, 1948. 



2 Heuse, O. Z- angew. Physik, 1953, 5 361. 



3 Ph. Miller, C, Hammond, C. W., Tompkins, M. and Shorter, G. J. Lab. din. 

 Med. 1951, 38 331, and 1952,39 462. 



* Rajewsky, B., Heuse, O. and Aurand, K. Z- Naturf. 1953, 8b 157. 



^ Rajewsky, B. and co-workers. Z- Natiirf., in press ; Strahlentherapie, in press. 



* WiLHELM, G. Strahlentherapie, in press. 



■^ ROMER, H. and Beller, F. K. 7. International Congress of Radiology, Copen- 

 hagen 1953. 



* Rajewsky, B. and Inouye, K. Naturwissemchaften, 1937, 25 540. 

 ^ Aurand, K. Strahlentherapie, in press. 



lOAuRAND, K. and Panly, H. Z- Naturf. 1954, 9b 506. 

 i^Panly, H. Strahlentherapie, in press. 



DISCUSSION 



M. V. Haigh : In work with Dr. Edith Paterson at the Christie Hospital, Man- 

 chester, on whole body irradiation of Rhesus monkeys, we also find evidence for a 

 so-called ' protective effect ' of an initial dose of X-ray followed by a second dose at 

 varying intervals later. In this time factor work, our L.D. 50 (30 days) is determined 

 by the probit method. For single session irradiation a series of animals were irradi- 

 ated at 450 r, 500 r, 550 r, 600 r, and 650 r respectively and the L.D. 50 was found to 

 lie between 500 r and 550 r, 20 animals being used in these latter two groups. 



In the 'time factor' experiments the initial dose of X-ray was fixed at 260 r 

 (approximately \ L.D. 50 for the single session). One group of monkeys then 

 received a second dose of X-rays seven days later and the total dose of X-rays was 

 then found to lie between 700 r and 750 r at L.D. 50 levels. Thus the comple- 

 mentary dose to the initial 260 r at 7-day interval is lower than the L.D. 50 dose for 

 single session. This shows that at 7 days the animals had not recovered from the 

 initial 260 r, and it has not shown a ' protective ' effect. A second group of monkeys 

 given an initial dose of 260 r were irradiated to L.D. 50 levels after an interval of 

 20 days. The L.D. 50 was found to lie between 850 r and 900 r (on the probit 

 graph at 880 r) and here the complementary dose of X-rays is 880 r — 260 r = 620 r 

 which exceeds the L.D. 50 level for single session. Here the animals have recovered 

 from their inidal 260 r and are apparently protected from a higher dose than they 

 would have survived in single session. This has also been shown to be true in mice* 

 The work has not been extended beyond the 20-day interval so that we have no 

 evidence as to whether after 30 days the protective effect of the initial dose is not 

 any longer apparent. 



* Paterson, Gilbert, Matthews. Brit. J. Rad. XXV No. 296, Aug. 1952. 



92 



