WALLACE O. FENN 



579 



these experiments, shows that these carbon particles (4.7^) should 

 collide with the cells only ^ or 0.36 times as often as the quartz 

 (4.08/1). It may be concluded, therefore, that carbon is ingested 



1.06 



or 3 times as readily as quartz. 



Results of all the other available comparisons between quartz 

 and carbon are plotted in Figs. 2 to 8 and tabulated in Table II. 

 In each experiment the initial K only was used in comparison unless 

 K was constant throughout. The last column in Table II shows 

 the number of collisions necessary for ingestion of one quartz particle 

 if every collision with a carbon particle results in ingestion; i.e., the 



TABLE II. 



Comparison of Rates of Phagocytosis of Carbon and Quartz by "Suspension" Method. 



Average = 4.0 

 * The calculated ratios are the ratios of the chances of collision for the sizes 

 of particles used as given in Table I. The corrected ratio is the quotient obtained 

 by dividing the observed ratio by the calculated ratio. 



value of the ratio 



K carbon 



In five out of seven experiments carbon 



K quartz 



is taken up 2.8 to 11.5 times as readily as quartz. In two instances 

 only, due to some uncontrolled factor, quartz is taken up sKghtly 

 more readily than carbon. The average of all shows that carbon is 

 taken up 4 times as readily as quartz. 



It should be observed that it is assumed that a large particle is 

 taken up as easily as a small particle if the number of colUsions are 

 equal. That this is true, at least within limits of error of these experi- 

 ments, was shown in the two previous papers (4, 5). It would appear 



