340 TEMPERATURE COEFFICIENT OF PHAGOCYTOSIS 



more or less during the experiment and that it is impossible to be 

 sure whether the particles are actually inside the cells or merely stuck 

 on the outside. Hence, if the particles stick on the outside more 

 rapidly than they are ingested, it becomes impossible to measure the 

 actual rate of ingestion or to determine the true temperature co- 

 efficient of ingestion. This is undoubtedly the explanation of the 

 low temperature coefhcient, 1.4, obtained by this method between 

 30° and 37°C. 



The results of one experiment by the suspension method is shown 

 in Fig. 5, where the percentage of particles not ingested is plotted as 

 ordinates against time in minutes as abscissae. Determinations were 

 made at 37°, 27°, and 23°C. Inspection of these curves shows that the 

 temperature coefficient is very low above 30°C. compared to that 

 below 30°C. To obtain a quantitative comparison, the times, T, 

 necessary for ingestion of 25, 50, and 75 per cent of the particles have 

 been compared. Here, again, the rate of the reaction is conditioned 

 in part by the viscosity of the medium, collisions taking place between 

 cells and particles with proportionally less frequency in the more 

 viscous medium at 23°C. The rate of the reaction, K, when corrected 

 for viscosity is, then, the reciprocal of the time necessary for the 

 ingestion of a given percentage of particles multiplied by the viscosity. 



^ = ^ (1) 



T 



The temperature coefficient, Qio, is now calculated according to the 

 formula 



Log Ki — Log Ki , , 



Log Oio = ^-T 7^- X 10 (2) 



t\. — H 



where t is the temperature, as already explained. In this case 

 the graph of log K against temperature is not a straight line 

 as in the case of Madsen and Watabiki's results. In the experiment 

 plotted in Fig. 5, Qio is 1.26 between 23° and 27°C., and 5.6 between 

 27° and 37°C., when the figures for comparison are taken at the 

 stage in the reaction when 50 per cent of the particles are ingested. 

 The values obtained at other stages (25 and 75 per cent) in the reaction 

 are given in Table II together with the results of seven other similar 

 experiments. While the variations in the experimental figures are 



