W. 0. FENN 863 



tures taken by Commandon' showing leukocytes being attracted toward starch 

 particles from distances many times their own diameter. The moving pictures were 

 speeded up so that the leukocytes seemed to move with great rapidity, pushing 

 erythrocytes violently aside but always moving directly toward the starch grain and 

 finally swarming over it in numbers and apparently "eagerly" devouring it. 



Another important complication is seen in studies of the effect of temperature on 

 phagocytosis. At low temperatures it has been observed that particles stick to the 

 cells but are not ingested.^ Here the difficulty seems to be that the cell is too rigid to 

 permit the penetration of the particle. As the temperature is raised there comes a 

 point when ameboid movement begins,^ spontaneous energy changes begin to occur 

 inside the leukocyte which result in alternate changes of the protoplasm from sol to 

 gel, and the general fluidity of the cell becomes such that large particles can enter. 

 At this transitional point the temperature coefficient of phagocytosis becomes very 

 high {Qio= 18), 4 a small change in temperature causing a large change in fluidity and 

 hence in phagocytosis. Similar changes in consistency have been invoked particularly 

 by Loeb'' in explanation of cell behavior and undoubtedly play an important part in 

 phagocytosis. 



There are, therefore, many factors other than surface tension which enter into 

 problems of phagocytosis. The cells have structure and show marked changes in their 

 consistency. Like all living matter, they are centers in which free energy is being made 

 available by oxidative reactions at a rate which might dwarf to insignificance the 

 energy changes due merely to transfer of an object from outside the cell to its interior. 

 Without losing sight of this fact, it is nevertheless clear that the cells are exposed to 

 these surface forces and that they are of sufficient magnitude to be of decisive im- 

 portance in the economy of the cell, at least under some conditions. In addition to 

 the example of the carbon and quartz which demonstrates this fact, two others 

 deserve mention. Thus Falk^ and his associates find a correlation between the viru- 

 lence of pneumococcus strains, their cataphoretic potentials, and their ingestibility 

 by phagocytes. Second, Mudd and Mudd^ have observed motile bacteria struggling, 

 mostly in vain, to escape from an oil-water interface in which they were held by sur- 

 face tension forces. And the higher the surface tension of the interface the more 

 firmly were they held. 



Such experiments point the way for future investigations and amply justify a 

 general and inclusive statement of the conditions necessary for equilibrium between 

 three immiscible phases, one of which may be solid. 



CONDITIONS NECESSARY IN PHAGOCYTOSIS FOR A MINIMUM OF FREE ENERGY 



The formula for the equilibrium is very simply explained in terms of the contact 

 angle. ^ When three fluids, or more commonly two fluids, and a gaseous phase are in 

 ' Commandon, J.: Compt. rend. Soc. de biol., 82, 11 71. 1919. 

 ^ Ledingham, J. C. G.: /. Hyg., 12, 320. 1912; Proc. Roy. Soc, B, 80, 188. 1908. 

 3 de Haan, J.: Arch, neerl. de physiol., 6, 388. 1921. -i Fenn, W. O.: op. cit., ^, 331. 1922. 

 5 Loeb, L.: "Washington University Studies," 8, 3. 1920. 



*FaIk, I. S., and Matsuda, T.: Proc. Soc. Exper. Biol. & Med., 23, 781. 1925-26. 

 'Mudd, S., and E. B. H.: /. Exper. Med., 40, 647. 1924. 

 * Maxwell, J. C: Encyc. Brit, (nth ed.), 5, 262. 1910-11. 



