588 



ADVENTURES IN RADIOISOTOPE RESEARCH 



to be made on the registered counts. Since counter 2 starts and finishes 

 counting 10 minutes later than counter 1, and during this time 1.1 per 

 cent of the ThB has decayed, the counts registered by counter 2 must 

 be increased by 1.1 per cent of their value. Similarly the counts registered 



c 

 E 

 en 

 o 



^ 200- 



< 



—I 1 1 1 ' 1 1 1 r- 



10 20 30 40 50 60 2 3 4 



Minutes Hours 



Fig. 2. Change in the activity of blood with time after injection 

 of thorium B labelled whole blood. 



by counters 3, 4, 5 and 6 have to be increased by 2.2 per cent, 3.3 per 

 cent, 4.4 per cent and 5.5 per cent, respectively, of their value, to make 

 them comj)arable with the counts registered by counter 1. 



Fig. 3. Change in the activity of the blood with time in a case of 

 polycythemia after injection of thorium B labelled whole blood 



We found it very convenient to place five secured and one standard 

 sample in an automatic sample chamber which shifts the samples every 

 10 minutes and registers — on six separate telephone counters— the counts 

 produced during the night. Even blood samples of very restricted activity 

 could be measured with satisfactory accuracy by this procedure, as seen 

 in Table 2. 



