WALLACE O. FENN 



457 



the fact that the error assumed is in general no larger than the prob- 

 able error. Reference to Table III will show that the ratios between 

 the three experimental constants agree fairly well with the theoretical 

 ratios.^ 



Experiments 3 and 4. — Two more experiments were tried in which only the 

 largest and smallest particles were compared. New suspensions were prepared 

 from the same stock and in the same way as before. The sizes are accordingly 

 somewhat different. The rates of phagocytosis are compared with the chances 

 of collision in Table IV, and the experimental points are plotted in Figs. 7 and 8. 



TABLE IV. 



Comparison of Theoretical and Experimental Rates of Phagocytosis of Two Sizes 



of Quartz Particles. 



Average diameter of particles. 



f Maximum. 

 Minimum. 

 Average. . . 

 Chances of collision 



Experiment 3 (Fig. 7) I ^"^\'^f^- 



Experiment 4 (Fig. 8) Initial K. 



Ratios. 



1:0.18 (Theoretical.) 



1:0.35 (Experimental.) 

 1:0.21 ( " ) 



1:0.38 ( 



) 



In Experiment 3 the reaction starts very slowly and for some 

 unknown reason the cells become changed or the medium becomes 

 more favorable so that they can ingest particles more readily. Each 

 reaction is, therefore, made up apparently of two distinct parts. If 

 the change in the cells in the two tubes is comparable the ratio of the 

 X's should be the same for the later K's as for the initial K's. This 

 turns out to be true and both ratios agree well with the theoretical 

 ratio. The inclusion of the later X's is admittedly somewhat arbi- 

 trary and is given merely for what it is worth. 



The graphs in Fig. 7 for the 3.18 ^ particles show considerable 

 irregularities but the agreement of the initial K's is very good and the 

 ratio of the initial K's for the two sizes of particles agrees fairly well 

 with the theoretical. 



^ A discussion of the significance of a constant K in view of the gradual agglu- 

 tination of cells is postponed to the next paper of this series. 



