5G2 



ADVENTURES IN IIADIOISOTOIE EESEAECH 



If we wish to determine the amount of circulating corpuscles we have 

 to know (a) the amount of the injected labelled corpuscles, (b) the activity 

 of 1 gm of these corpuscles, and (c) the activity of 1 gm corpuscles secured 

 from the circulation after mixing, (a) The amount of injected corpuscles 

 is obtained from the volume of the injected blood, the specific weight 

 of the corpuscles (1.08), and the hematocrit value. (6) The activity of 

 1 gm of these corpuscles is found from measuring the activity of 1 gm 

 corpuscles of our standard preparation mentioned above, (c) The activity 

 of 1 gm corpuscles secured from the circulation after mixing is found 

 when measuring the activity of 1 gm corpuscles secured 5—10 minutes 

 after the injection. 



Let us denote the amount of corpuscles injected into the circulation 

 by A, the ratio of the activity of 1 gm corpuscles of the injected blood 

 and of the activity of 1 gm corpuscles secured from the circulation after 

 the injection by B, then the total amount of the corpuscles present in 

 the circulation (X) is given by 



X = A-B 



The blood sample is secured in the interval between 5 and 10 minutes, 

 preferably after the lapse of 5 minutes, following the injection. 3 minutes 

 after the injection, a mixing of the reinjected labelled blood with the 

 non-labelled one might possibly not have occurred. On the other hand, 

 the loss of activity by the corpuscles might become noticeable after the 

 lapse of 10 minutes. Table 1 illustrates the above statement. 



Table 1 



Sources of error 



Three main sources of error have to be considered. (A) The centrifuged 

 corpuscles are not free from plasma. (B) We do not inject active corpuscles, 

 but active blood, and some radio-phosphorus may enter the corpuscles 

 during the interval between the injection of labelled blood and the 



