DETERMINATION OF RED CORPUSCLE CONTENT 



527 



(of. Table 2). If the plasma activity would disappear with the same speed 

 in experiments in vitro as in experiments in vivo we would obtain the 

 figures seen in the 5th column of Table 2. 



The following example shows how column 5 of Table 2 was calculated. 

 Calculation of the value obtained after 2 min. The average activity of 

 1 gm plasma during the 3 first minutes can be estimated to be 500. As, 

 after 3 min, in the experiment in vitro 1 gm corpuscles was found to 

 contain 5.4% of the activity of 1 gm plasma, the figure registered in 

 column 5 works out to be 2.7. The average activity between 3 and 6, 

 and between 6 and 12 min, respectively, is estimated to be 200 and 130, 

 respectively. 



When comparing the activity of the corpuscles with the activity of 

 the plasma, we can calculate the increase in activity of the corpuscles 

 and compare this activity increase with the activity of the corpuscles 

 which we inject in our usual experiments in which blood is shaken with 

 active phosphate in the thermostat before the injection. 



Table 2. — Penetration of ^^P of the Plasma into 

 THE Corpuscles after Injecting Labelled Plasma into 



THE Rabbit 



Adhesion of Active Plasma to the Corpuscles 



The activity of the plasma may also influence the results obtained in 

 another way as mentioned above. Centrifuging of blood does not lead 

 to corpuscles entirely free of plasma. After centrifuging blood for 25 min, 

 in a centrifuge making 5000 revolutions per minute, we find the cor- 

 puscles to contain 2% plasma (cf. also Hahn and Hevesy, 1942). In 1 

 gm corpuscles prepared from the blood to be injected, we shall therefore 

 find only 0.98 gm corpuscles, the remainder being composed of plasma. 

 In the blood to be injected, the activity of 1 gm corpuscles is about equal 

 to the activity of 1 gm plasma, and the error due to the presence of plasma 

 in the blood injected can thus be disregarded. However, other conditions 

 prevail in the blood samples secured from the rabbits at different times. 

 In the last mentioned samples, the adhering plasma is much less active 



