WALLACE O. FENN 591 



optimum coagulation between 0.0003 and 0.005 m hydrochloric acid 

 (probably at 0.001 in the case of quartz). The results, therefore, 

 neither prove nor disprove the hypothesis although they do indicate 

 that carbon carries a negative charge contrary to the evidence from 

 the literature. Also, the greater stability of quartz as compared to 

 carbon in all concentrations of hydrochloric acid appears to prove 

 that stability (and hence probably phagocytosis) is conditioned by 

 some factor besides the electric charge, presumably the surface 

 tension. 



There are many valid objections (McClendon (18), Hyman (19), 

 and Loeb (20)) to the explanation of ameboid movement by surface 

 tension changes on account of the more or less rigid ectoplasm of the 

 cell. In so far as phagocytosis is Hmited by ameboid movement, 

 these objections also apply to the explanation of ingestion of particles 

 by surface tension. The ingestion of quartz in these experiments, 

 however, is not limited by the ameboid movement of the leucocytes 

 which is sufficiently vigorous to cause ingestion of carbon at a more 

 rapid rate. It is, therefore, a question of molecular attractions 

 between particle and cell, and these are best expressed in terms of 

 surface tension. 



The analogy between this hypothesis and the sometimes parallel 

 effects of opsonins and agglutinins has been suggested to the writer 

 by Dr. W. B. Cannon. Thus, Bull (21) in a series of papers has 

 brought out the fact that bacteria injected into the circulation are 

 removed more rapidly, apparently by phagocytosis, when agglutinated 

 by immune serum. Zinsser (22) quotes Ottenberg as authority for 

 the statement that phagocytosis of foreign red cells in the circulation 

 after blood transfusion occurs only when the patient's serum has an 

 agglutinative action on the donor's cells. Likewise, Ledingham (23) 

 has pointed out "that the opsonin-bacteria like the agglutinin-bac- 

 teria are probably in a more precipitable condition than non-sensitized 

 bacteria. They are, in fact, as I have frequently observed, in a con- 

 dition of extremely fine aggregation, and if the sensitizing fluid has 

 marked agglutinating powers the sensitized organisms are frankly 

 clumped." From this evidence it appears that bacteria as well as 

 solid particles are more readily ingested when easily agglutinated. 



