706 



ADVEXTURES IX RADIOISOTOPE RESEARCH 



the extracellular P corresponds closely to the activity of the free plasma 

 phosphorus. The extracellular share of the free sarcoma phosphorus, 

 however, is small and, since the activity of the sarcoma phosphorus 

 does not differ considerably from that of the plasma phosphorus, the 

 error committed in disregarding the complex nature of the free sarcoma 

 phosphorus is not important. The rat 47 : 1, for example, contains 

 1.45 mgm % of extracehular P and 44.8 mgm % of intracellular P. These 

 figures are obtained by assuming that one-quarter of the sarcoma con- 

 sists of extracellular fluid in conjunction with the P content of the plasma 

 (5.8 mgm %) and of the sarcoma (46.3 mgm %). The specific activity of 

 the 1.45 mgin % of extracellular P is 5 per cent higher than that of the 

 44.8 mgm % of intracellular P (see Table 8) ; by neglecting the extracellular 

 quota, therefore, the specific activity of the intracellular P is overestim- 

 ated by 0.07/44.8 = 0.14 per cent. 



With regard to the sarcoma cells there is possibly a hmited effect of 

 irradiation on their permeability. Whereas the ratio of the activity of 

 1 mgm of sarcomaP to that of 1 mgm of plasma P in unirradiated sarco- 

 mas is on the average 1.07 (see Tables 8 and 9), the corresponding 

 ratio in irradiated sarcomas is 0.94; this difference, however, cannot 

 explain the major part of the observed effect. 



Nucleic Acid Metabolism and Phosphate Permeability of the Necrotic 

 Sarcoma Tissue 



It is shown in Table 8 that the nucleic acid formation in necrotic 

 sarcoma tissue is indeed considerably less than in fresh tissue but that 



Table S. — Nucleic Acid Formation in Unirradiated Sarcomas 



