WALLACE O. FENN 



583 



tension by some long contracting pseudopod- which had suddenly suc- 

 ceeded in pulling the cell loose from its contact with the slide. Toward 

 the end of an experiment the cells are usually aggregated in groups, 

 mostly heavily laden with particles. This clumping is also found, 

 apparently to the same extent, in a control preparation from which 

 particles are omitted. Often cells are so full of particles that close 

 inspection is necessary to see protoplasm at all. 



Number parricles 

 free 



Number patTicle^ 

 free 



i z 5 hours 4 



Fig. 10. 



I 2 3 Hours 4. 



Fig. 11. 



Figs. 10 and 11. Comparison of phagocytosis of carbon and quartz by the 

 film method. The numbers of particles not yet taken up in a given area are 

 plotted as ordinates against time in hours as abscissae. Here no appreciable al- 

 lowance need be made for the chances of collision, and carbon is obviously 

 ingested more rapidly than quartz. See Table III for further analysis. 



The results of two typical experiments of this sort are plotted in 

 Figs. 10 and 11. Ordinates represent the number of particles of 

 quartz or carbon counted over a given area which are still outside 

 the cells. Time is plotted as abscissae. Inspection shows that the 

 carbon is taken up more readily than the quartz. The question is 

 how much more readily. Here the data can be analyzed with more 



^ Such pseudopods have been described by Kite (Kite, G. L., /. Infect. Dis., 

 1914, XV, 319). 



