440 PHAGOCYTOSIS OF SOLID PARTICLES. I 



Madsen and Watabiki (3) have avoided this difficulty, in measure- 

 ments of the rate of phagocytosis of bacteria at different temperatures, 

 by measuring the time curves of the number of bacteria taken up per 

 leucocyte at each temperature. By certain assumptions they suc- 

 ceeded in fitting their experimental curves to the formulas for mono- 

 molecular or bimolecular reactions, and thus determining a constant, 

 K, which represented the rate of the reaction. There seemed to be in 

 this case, however, no particular significance to the obedience of the 

 curves to the laws for chemical reactions. 



In the experiments on phagocytosis of soKd particles to be described 

 in this paper it was found possible to avoid the objections in former 

 methods and to analyze the reactions quantitatively in terms of the 

 number of collisions occurring between cells and particles. To 

 accomplish this, particles of carbon or quartz of uniform size were 

 incubated with leucocytes. At frequent intervals a sample was 

 removed to an ordinary blood-counting chamber and the number of 

 particles not taken up by the leucocytes was counted. 



If the number of cells present is large and remains constant through- 

 out the experiment, the number of collisions varies only with the num- 

 ber of particles, and it should be possible to calculate the rate of phago- 



1 



cytosis, K, from the equation for a monomolecular reaction, K = - 



A . ^ 



log ; where A is the number of particles originally present and 



A — X 



X is the number ingested by the leucocytes in the time, /. The fact 

 that K is usually found to be constant shows that we are dealing with 

 a process like a monomolecular reaction in which the collisions can 

 be watched under the microscope. The leucocytes can take up so 

 many particles that their capacity does not diminish sufficiently to 

 hmit the rate of the reaction. Certain uncontrollable complicating 

 factors which cause K to vary will be discussed with the experimental 

 results and in a subsequent paper. 



A constant K, calculated in this way, means that the same per 

 cent of the particles present is being ingested per unit of time; i.e., 

 K is independent of the actual number of particles present. In other 

 words, it is not the number of collisions but the chances of collision which 

 determine K, other things being equal. Since the chances of colHsion 



