WALLACE O. FENN 



383 



served behavior of leucocytes means either that the rigidity of the cell 

 prevents its reaching a true equilibrium on a flat surface, or that it 

 ingests, by its ameboid movement, a small particle of G which other- 

 wise would be merely stuck on the outside. Both alternatives seem 

 equally probable. Obviously such tests of the surface tension hypo- 

 thesis are worthless. 



TABLE I. 



Areas of Contact Surfaces during Ingestion of a Particle. 



y expresses the degree of ingestion as shown in Fig. 3. Ingestion is complete 

 at 0.5y, one-half complete at 0.22v. s is the area of the cell in contact with the 

 particle; Ax the change in the area of the cell plasma interface; A is the angle 

 of contact. 



Is it easier to ingest a small particle than a large particle, and if 

 so, why? Tait says: " If in the case of a given phagocytic cell we have 

 a certain volume of material which can just be ingested as a spherical 

 piece, that cell will ingest the same volume more readily when the 

 material is either sub-divided or distorted from the spherical form for 

 by this means s is increased without change in x [Ax in our terminol- 

 ogy]." It is true from principles of surface tension that a large 

 particle will be less completely ingested than a small one for the same 

 values of m and n, i.e., for the same contact angle, but the same limit- 



77% 



ing values of m and n (i.e., = 1) arc necessary for complete in- 



n 



gestion of any particle of any shape or size. It is true, however, 

 that a small particle could be more easily pulled inside against the force 

 of surface tension from some equilibrium position in the surface than 



