WALLACE O. FENN 335 



sion. Since this formula was based on Stokes's law for falling bodies, 

 the chances of collision are inversely proportional to the viscosity of 

 the medium. In the previous experiments the viscosity could be 

 neglected because it did not vary. Where temperature is the variable, 

 however, it is obvious that the viscosity becomes a factor of some sig- 

 nificance because it decreased proportionally the number of meetings 

 between leucocytes and bacteria. The rates of phagocytosis cal- 

 culated by the improved method were, therefore, corrected by mul- 

 tiplying by the viscosity of water as given in Landolt and Born- 

 stein's tables before plotting. If the same correction had been applied 

 to the original values of K they would have given a temperature 

 coefficient less than the new values. The correction for viscosity 

 decreases the value of Qi^, as shown in Table I, but does not appreci- 

 ably affect the form of the curve. 



It is conceivable that the number of collisions between bacteria 

 and leucocytes might be so great that this would not be a limiting 

 factor. In experiments on the phagocytosis of solid particles this 

 certainly was not the case since the number of particles ingested in a 

 given time was always a constant percentage of the number present. 



The last column in Table I gives values for ^lo obtained when the 

 time is measured from the end of the latent period instead of the 

 beginning, the correction for viscosity also being made. This pro- 

 cedure gives a slightly lower value for (2io- 



We may take, then, for the temperature coefficient of phagocytosis, 

 as nearly as it may be obtained from these experiments, the value 

 2.0.3 



This figure is not thoroughly satisfactory, however, because the 

 curves in Figs. 1 and 2 are complicated by at least two reactions, each 

 with its own temperature coefficient, besides the phagocytic reaction 

 proper. 



The first of these reactions is represented by the latent period. 

 Madsen and Watabiki calculated its temperature coefficient from the 



' Ledingham, in studying the effect of temperature on phagocytosis of bacteria, 

 concluded that it was due to the different rates of adsorption of opsonin by the 

 bacteria. By previously incubating the bacteria with serum the accelerating 

 effect of temperature could be nearly excluded. (Ledingham, J. C. G., Proc. 

 Roy. Soc. Biol, B. 1907. Ix.xx, 188.) 



