690 ADVENTURES IN RADIOISOTOPE RESEARCH 



in the first phase of the experiment, corpuscles containing inactive 

 nucleic acid reach the circulation, and that it is about four days before 

 corpuscles containing labelled nucleic acid are given off by the sinusoids 

 to the circulation. The maturing of the corpuscles in the marrow thus 

 takes about four days. The graph also shows that, after the lapse of 

 about thirty-three days, the maximum value of the activity of the 

 desoxyribose nucleic acid is reached. Taking into account that in the 

 first four days no labelled corpuscles intrude into the circulation, the 

 life-time of the red corpuscles will be 29 days. It is of interest finally 

 to note that the results obtained indicate that all or almost all corpuscles 

 present in the circulation have a similar life-time. 



