'riivMis I'UNcnio.N a.nd LVMi'iiotivn: homeosiasis 



to multiplication if present for lonu, enf)Uiz:li, niiujht eventually induce neo- 

 plasia in the target cells, i.e., the 1\ niphoid tissues. 



The present evidence of elevated L.S.F. levels developing in mice subjected 

 to whole-body irradiation is of considerable interest in view of the leukaemo- 

 genic effect of whole-body irradiation in mice. 



It suggests that, in mice, irradiation-induced lymphoid leukaemia may 

 share a common ]-)atlu)genesis with the spontaneous disease. Ihis would fit 



X- rays 



Leukemogenesis 

 after whole -body 

 irradiation 



Thymus function 

 after whole-body 

 irradiation 



Figure 2. Comparison between the indirect mechanism of 

 leukaemogenesis following irradiation proposed by Kaplan^ 

 and the effect of irradiation on thymic L.S.F. production 



well the indirect mechanism by which Kaplan^ has conceived irradiation 

 induces lymphoid leukaemia in mice {Figure 2) and the paramount role 

 played by the thymus in this process. 



REFERENCES 



lAuBERTiN, C. Bull. Soc. Rudiol. med. Paris 40 (1931) 218 



^Krebs, C, Wagner, A. and Rask-Nielsen, H. C. Acta, radiol., Stockh. Supplement 



10 (1930) 1 

 3FURTH, J. and FuRTH, O. B. Amer. J. Cancer 28 (1936) 54 

 ^Kaplan, H. S. /. nat. Cancer Inst. 11 (1950) 83 

 ^Kaplan, H. S. Cancer Res. 14 (1954) 535 



6 Law, L. W. and Potter, M. Proc. nat. Acad. Sci., Wash. 42 (1956) 160 

 'Metcalf, D. Brit. J. Cancer 10 (1956) 442 

 ^Metcalf, D. and Buffett, R. F. Communication to the Seventh International Cancer 



Conference London, 1958 



^Metcalf, D. Radiation Res. 1958 — in the press 

 i^Metcalf, D. Proceedings of the Third Canadian Cancer Research Conference: Academic 



Press Inc., New York, 1959 — in the press 



28 



