WALLACE O. FENN 



481 



In general it was found in these experiments that anything which 

 increased clumping also increased phagocytosis and vice versa. Thus, 

 the higher the concentration of sodium citrate, the less the phago- 

 cytosis and the less the clumping.^ With washed cells from which 

 all the fibrinogen has been removed, the number of free cells shows 

 only a gradual decrease during the experiment. 



% of Cells confaining' 

 Carbon 



1 



t 1 r 



2 3 Hours 4 



Fig. 8. Ordinates represent the per cent of the unclumped cells counted in 

 Fig. 7, which contained carbon. Curves show that serum which accelerates 

 clumping cells also accelerates phagocytosis. The similar effect of Ringer's solu- 

 tion shows that the calcium in serum is partly responsible for its effect. 



SUMMARY. 



1. By measurements of the diameter and velocity of leucocytes 

 and of the particles in two carbon suspensions, the relative rates of 

 ingestion of the two suspensions by the leucocytes are predicted and 

 the predictions verified experimentally. 



2. The results indicate that 4.7ju particles of carbon are ingested 

 as readily as S.l/x particles. The more rapid apparent rate of inges- 

 tion of the 4.7/x particles is due to their greater availability rather 

 than the greater capability of the leucocytes. 



^ Mcjunkin (Mcjunkin, F. A., Arch. Int. Med., 1918, xxi, 59) has used the 

 abihty of white blood corpuscles to ingest carbon in varying concentrations of 

 sodium citrate as a means of classification. 



