RED CORPUSCLES OF THE HEN" 



689 



example, labelled phosphate to the hen, and after the lapse of a week 

 replace part of the corpuscles of a second hen by labelled corpuscles 

 of the first one. When taking blood samples at intervals, we can deter- 

 mine what percentage of the transfused corpuscles is still present in the 

 circulation of the hen. In a note to be published later, we shall commu- 

 nicate the results obtained in such experiments. In this note we shall 

 describe another method in which, by avoidance of blood transfusion, 

 the uncertainty about the equality of the life-time of the transfused 

 corpuscles and the endogenous corpuscles can be eliminated. 



100 

 80 

 60 

 40 

 20 



/ 



9 



/ 



10 



20 



30 



40 



Life-cycle of the red coipuscles of two hens. Abscissae : days after 

 start of experiment ; ordinates : specific activity of desoxyribose- 

 nucleic acid phosphorus extracted from the corpuscles secured at 



different dates. 



In the latter method, labelled phosphate is administered twice a day 

 to the hen in such quantities that the plasma phosphate is kept at a 

 constant or almost constant level of activity. The active phosphate 

 penetrates into the marrow and participates in the formation of the 

 nucleic acid of the corpuscles, which thus become labelled. The percentage 

 of labelled corpuscles will increase with time, and finally the circulation 

 will contain labelled corpuscles only; thus the activity of 1 mgm cor- 

 puscle desoxyribose nucleic acid phosphorus will be equal to the activity 

 of 1 mgm marrow phosphorus and I mgm plasma phosphorus re- 

 spectively. 



The results of such experiments are shown in the accompanying graph, 

 which makes it clear that in the first four days the nucleic acid present 

 in the corpuscles is inactive. This may be interpreted by assuming that. 



44 Hevesy 



