526 ADVENTURES IN RADIOISOTOPE RESEARCH 



above data — after shaking the blood at 37° for 2 hours, the ^sp : 3ip 

 ratio of the plasma is still about 10 times the corresponding ratio in the 

 corpuscles. 



Errors due to the Activity of the Plasma 



We do not inject active corpuscles but active blood into the circulation 

 of the rabbit. The plasma of the rabbit becoming thus active, some active 

 phosphate will penetrate into the corpuscles in the course of the experi- 

 ment, increasing thus the ^^p content of the corpuscles. Such a process 

 may entail a source of error. If, besides the corpuscles injected, labelled 

 corpuscles are formed in the circulation, the value calculated for the 

 erythron from the dilution figures will clearly be found too low. In order 

 to estimate the error due to the above mentioned process the following 

 experiment was carried out. Active plasma is injected into the blood of 

 a rabbit and blood samples are secured at different times. The corpuscles 

 are separated and their activity is determined. The figures obtained 

 (cf. Table 2) show what percentage of the plasma activity enters the 

 corpuscles during the experiment (3 to 12 min), similar values being 

 obtained in further experiments. In our red corpuscle determination, the 

 activity of 1 gm corpuscles injected was about the same as the activity 

 of 1 gm plasma injected, i. e. in the relative units of Table 2 = 1000. 

 Therefore the figures of the 4th column of Table 2 give almost exactly 

 the percentage error of the red corpuscle determination due to the 

 penetration of ^^P from the plasma into the corpuscles in the circul- 

 ation of the rabbit. 



It is of interest to compare the rate of penetration of ^sp from the 

 plasma into the corpuscles in experiments in vitro with the figures 

 obtained in the above described experiment in vivo. 



Experiment in vitro 



Inactive blood was brought to 37° in the thermostat, active plasma 

 of negligible weight was then added and the activity of the corpuscles 

 was determined at different times. After the lapse of 3, 6 and 12 min, 

 respectively, the corpuscles were found to contain 5.4%, 8.8%, and 

 12.9%) of the activity of the plasma. These figures were corrected for 

 the activity due to adhesion of active plasma to the corpuscles which 

 was found to make out 2%, of the plasma activity. In experiments in 

 vitro in which the plasma activity does not much change during the 

 experiment the activity penetrating into the corpuscles during 3 to 12 

 min is thus quite appreciable. In experiments in vivo, however, the 

 plasma activity rapidly decreasing after the injection of the active 

 blood, the amount of ^sp penetrating into the corpuscles is much smaller 



