INDIRECT EFFECT OF X-RAYS OX THE JENSEN-SARCOMA 



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in a sarcoma is depressed by the action of X-rays, and we have used this 

 method for studying the question of whether and to what extent a sar- 

 coma protected against the direct effect of radiation is affected by irra- 

 diating other parts of the body. For this purpose we inoculated rats with 

 two sarcomas, the one sarcoma being irradiated and the other being 

 protected against the effect of X-rays by a covering of lead. Radio- 

 active sodium phosphate was injected after irradiation. Two hours later 

 the rats were killed and the deoxyribonucleic acid was isolated from 

 both sarcomas. Comparison of the radioactivity of the two fractions 

 with each other and with the activity of nucleic acid samples which had 

 been obtained from the sarcomas of unirradiated controls permits answers 

 to be given to the questions formulated above. 



EXPERIMENTAL 



In the first series of experiments rats w^ere used in which both sarcomas 

 were growing on the left and right of the back. The shortest distance 

 between the sarcomas was about 4 cm. One sarcoma was protected 

 against the effect of irradiation with a lead sheet at least 5 mm thick. 



Table 1. — Formation of Nucleic Acid in Unirradiated Sarcomas. 

 The other Sarcoma Irradiated with 280 — 2000 r 



