956 ADVENTURES IjS" RADIOISOTOPE RESEARCH 



The determination of the total corpuscle volume of the organism 

 demands only that the labelled corpuscles retain their labelling for some 

 minutes; the determination of the life-cycle of the corpuscles requires, 

 however, the use of marked corpuscles which conserve their labelling 

 for weeks. No worker has yet succeeded in achieving a labelling of mam- 

 malian red corpuscles that fulfils this condition. Iron-labelled corpuscles, 

 although remaining labelled for a sufficient time, were found by Hahn 

 and his colleagues^^^^ not to be suited to the purpose in hand. The life of 

 the red corpuscles of the hen, however, was determined,^^^^ making use 

 of phosphorus-labelled corpuscles. In contradistinction to mammalian 

 corpuscles, avian corpuscles contain large amounts of desoxyribose 

 nucleic acid, and the nucleic acid molecules were found to remain un- 

 changed throughout the life of the corpuscles. The newly formed corpusc- 

 les of a hen to which labelled phosphate is administered contain label- 

 led desoxyribose nucleic acid. 



By daily injection of labelled phosphate, the activity of the plasma 

 phosphate is kept at a constant level, and at suitable intervals the spe- 

 cific activity of the nucleic acid P extracted from the corpuscles is deter- 

 mined. Figure 9 illustrates the results obtained, including the fact that, 

 after the lapse of about 33 days, the specific activity of the nucleic acid 

 P became constant. This indicates that all corpuscles present in the 

 circulation of the hen were formed during the experiment. In the cor- 

 puscle samples taken in the course of the four first days, only minute 

 amounts of labelled nucleic acid were found to be present. This may 

 be interpreted by supposing that the formation of the corpuscles in the 

 marrow, up to the point of their release into the circulation, requires 

 four days. 3.5 per cent of the corpuscle content of the hen is thus built 

 up daily. 



I have attempted to give a short review of the earliest applications 

 of isotopic indicators and to discuss a few examples of their earlier and 

 more recent employment. Their use may be much extended in the time 

 to come. 



References 



1. G. Hevesy and F. Paneth, Z. anorg. Chem. 82, 322 (1913). 

 G. Hevesy and E. R6na, Z. phys. Chem. 89, 294, 303 (1915). 



2. F. Paneth and G. Hevesy, Monatshefte 36, 75 (1915). 



3. G. Hevesy, Phys. Z. 16, 59 (1915). Comp. also O. Ebbacheb, Z. phys. Chem. 

 A 163, 196 (1933). 



4. G. Hevesy and M. Biltz, Z. phys. Chem. B 3, 271 (1929). 



5. F. Paneth, Z. Elektrochem. 28, 113 (1922). 



6. F. Paneth, Radio Elements as Indicators. New York (1928). 



7. F. Paneth and E. Winternitz, Ber. 51, 1728 (1918). 



8. F. Paneth and O. Nobbing, Ber. 53, 1693 (1920). 



