WALLACE O. FENN 



453 



Substituting this value for K in the third column of Table II we have 

 the true values for the velocity in the last column. These were the 

 data used in calculating the chances of collision. 



TABLE II, 



Diameters and Velocities of the Three Groups of Leucocytes. 



From these data the density of the cells may be determined by 

 equation (3). 



5.1 X 1.64 



D - d = = 0.105 



8.92 



D = 1.007 + 0.105 = 1.11 



Comparison of the Rates of Phagocytosis of Quartz Particles of Three 



Different Sizes. 



Experiments 1 and 2. — The three quartz suspensions were washed once with 

 distilled water and were then allowed to settle at room temperature. After the 

 sharp boundary of the suspension had settled 3 or 4 cm. from the top of the 

 liquid, a definite amount, about 2 cm., was siphoned off the top of each suspension 

 as already described. From the minimum and maximum velocities so obtained, 

 the average velocity is calculated by equation (2) (Table III). The diameter is 

 then given by equation (3), and the chances of collision with the leucocytes by the 

 formula 



RaPa + RbPb + RcPc 



^total = 



100 



(5) 



where Ra, Rb, and Re are the chances of collision with the three groups of cells 

 a, b, and c; and Pa, Pb, and Pc, the percentages of cells in these groups. The 

 velocity of the 2.55^ particles being most nearly equal to that of the cells, these 

 particles have the smallest chance of collision, as shown in Table III. Under the 

 microscope these suspensions appeared as absolutely uniform as any suspension 

 of irregular particles could be (Fig. 4). 



