2Q8 PHYSICAL EXPLANATION OF PHAGOCYTOSIS 



find their way to the top before coagulation occurs, though the 

 process appears to continue after that), and the only alternative is 

 a physical attraction between the glass and the leucocytes. This 

 is a perfectly feasible explanation, and if it is true the next stage 

 in the process would necessarily follow. This is the flattening 

 out of the leucocytes, so that they form thin plaques of very much 

 larger diameter than the same cells as seen in ordinary wet films. 

 This is very difficult to explain as any vital effect, but it is 

 exactly what we should expect to happen if the leucocyte (which, 

 like all, or almost all, forms of living protoplasm, is to be regarded 

 as a liquid) were pulled out under the influence of surface tension, 

 just as a drop of liquid paraffin is stretched out into an infinitesi- 

 mally thin film when dropped on the surface of water. 



The bizarre forms which the leucocytes assume in a preparation 

 made by Ponder's method, with long pseudopodia, are explicable 

 on the assumption that, owing to irregularities in the cover-glass, 

 the surface tension is not uniform in all directions, or that the 

 protoplasm of the leucocyte is not of the same degree of viscidity 

 throughout. Similar irregular protuberances can be produced in 

 globules of oil or water by purely physical means, and Pauli goes 

 so far as to say that " since the discovery of the amoeboid move- 

 ments of oil droplets, and the careful physical analysis of this 

 process by Quincke, the formation of pseudopodia has been 

 robbed of the characteristics of a specific life phenomenon, and 

 later investigations have shown that it is governed in all its 

 details by the laws of surface tension. The taking up of food and 

 the process of defalcation in rhizopods can also be explained in 

 the same way." The process of the ingestion of an opsonized 

 bacterium suspended in serum at the body temperature, in which 

 it is occasionally possible to see the protrusion and seizure of the 

 organism by a long, slender, and flexible pseudopodium, is 

 explicable as follows : Owing to the change of surface tension 

 induced by the action of the opsonin on the bacterium, there 

 is generated an attractive force which tends to draw the two 

 together. The leucocyte, being fixed to the cover-glass like a 

 sucker, does not move, but a small portion of its substance, being 

 liquid or semi-liquid in consistency, is drawn out until it meets 

 the bacterium, which is, of course, also attracted. The two meet, 

 and then it will be found that the organism is firmly held in 

 contact with the pseudopodium, so that it is not released even if 

 the latter be carried to and fro by currents in the fluid. 



