APPLICATIONS OF ISOTOPIC INDICATORS 



955 



dog. Radio-iron has a much longer half-Hfe period than has radio-phos- 

 phorus; such "iron-labelled" corpuscles remain labelled for a much 

 longer time than "phosphorus-labelled" corpuscles. While, however, the 

 latter can easily be obtained by shaking blood with labelled phosphate, 

 the former can be made only in the living organism, a fact which, together 

 with the relatively great difficulty of obtaining radio-iron, restricts 

 the applicability of iron-labelled corpuscles in the determination of the 

 erythrocyte volume. 



o" 



in 

 jO" 



o" 



to 

 o 



O oa 

 O 



^ 



6 



Percentage "P administered present in 1 nngm nucleic acid 

 extracted from thie corpuscles 



