INDIRECT EFFECT OF X-RAYS ON THE JENSEN-SARCOMA 7o ( 



Summary 



Two Jenscu-sarcomas were injected into each rat. One sarcoma was irradiated 

 with about 2000 r and the other was protected from the effects of radiation by 

 means of lead. Control measurements with a Sievert's ionometer showed that 

 the dose received by the shielded sarcoma amounted at most to I per cent of 

 the dose received by the irradiated sarcoma (20 r or less). 



The determination of the foiination rate of deoxyribonucleic acid in the two 

 sarcomas, using radioactive phosphorus as a tracer, showed that in the fii-st 2 hr 

 after irradiation the formation rate in the shielded sarcoma fell only a httle short 

 (20 per cent) of the inhibition of the formation rate in the irradiated sarcoma. 



The volume increases of the irradiated and shielded sarcomas were also com- 

 pared. Three or four times 500 r were supphed in these experiments at 2-day 

 intervals. During the days of irradiation the daily percentage volume increase 

 scarcely differed, but in the subsequent 8 and 6 day periods the value for the 

 irradiated sarcoma was only about one-half that for the shielded sarcoma. 



Thus, there is also an indirect effect of X-rays on the sarcoma, but this effect 

 diminishes with time considerably more quickly than the effect obtained as a 

 icsult of direct irradiation. 



