WALLACE O. FENN 585 



/per cent Carbon\ 

 The ratio of these values I -j. — ) for carbon and quartz 



(last column) is then a measure of the greater speed of ingestion of 

 carbon. Strictly these figures should now be corrected by dividing 



{C + P) carbon^ 



by the ratio 777", jz: — which is a measure of the relative chances 



•' {C + P) quartz 



of collision. Since the value of this factor is small (1.07 and 1.2), 



this correction has not been applied, but the necessary factor for 



correction is given for each comparison. 



. .- . per cent Carbon 



It IS a very significant fact that this — 7-7; — ratio increases 



per cent Quartz 



after the 1st hour. This means that in comparison to carbon it is rela- 

 tively harder to ingest quartz toward the end of the experiment than 

 at the beginning. Thus, in Experiment 8 (Fig. 10), if every meeting 

 between a cell and a carbon particle results in ingestion throughout 

 the experiment, we may conclude that at the beginning of the experi- 

 ment two meetings with quartz are necessary for ingestion, and at the 

 end of the experiment, eight meetings. Eventually, carbon also is 



per cent Carbon 



refused and the ratio —7: ~ necessarily decreases again. 



per cent Quartz -^ *= 



This happens in Experiment 9 (Fig. 11). If the phagocytic activity 

 of the cells remained the same throughout an experiment, the per- 

 centage of carbon particles ingested during each hour would be con- 

 stant. The rate of decrease of this percentage may, therefore, be 

 taken as a measure of the rate at which the activity of the cells 

 decreases. Thus, in Experiment 8, the phagocytic activity of the 

 cells after 3 hours is only 54 or 24 per cent of the original. This may 

 be due to contact with the glass, agglutination of cells, decreased 

 capacity of cells, or other factors. 



Data from Experiments 10 and 11 are also included in Table 

 IV. The former is the only exception to the rule that the ratio 



per cent Carbon 



; — TT r increases after the 1st hour. In this experiment 



per cent Quartz 



both quartz and carbon (particularly quartz) were taken up more 



slowly even during the 1st hour than in the other three experiments, 



and it therefore seems probable that the decrease in the ratio in 



