192 



ADVENTURES IN RADIOISOTOPE RESEARCH 



Table 1. Labelled P Contents 

 OF Plasma and Tibia of a Frog 



Wt. 45 gm: temperature 22°; 



Determinations o min after the start 



of the experiment 



Friiclion 



^^1' content per 



mgm P (specific 



activity) 



Plasma ' 100 



Epiphysis | 0.020 



Diaphysis 0.013 



Epiphysis 



Fig. 1. Extent of replacement of frog's bone P by 



labelled P 



<'onstituents of the tibia contained some labelled phosphate, as shown in 

 Table 1. 



With increasing time, the ^-P content of the mineral constituents of the tibia 

 increases (Fig. 1). .After the lapse of 1 hr., the specific activity- of the epiphysis 

 P amounts onh- to 1/600 of the corresponding magnitude of the inorganic P of the 

 j)lasma. Thus only l/tiOO or less of the epiphysial P was replaced by plasma P within 

 1 hr. In the next 3 hr. a further 1/900 part of the epiphysis P exchanged. The 

 first point in the curve was obtained by anal\sing the right, the second point b>- 

 analysing the left tibia. For the diaphysis, the corresponding figures were found 

 to be 1/900 and 1/1200, respectively. In the course of 4 hr., therefore, only a minute 

 part of the tibia P is replaced by plasma P. A still smaller replacement is fovuid 

 when the frog is kept at 0°. 



