172 The Structure of Protoplasm 



few granules in it. I have not been able to see either the solation 

 at the posterior end or the gelation that extends the wall of the 

 body forward, yet from the manner in which it migrates, it seems 

 as though exactly the same fundamental events must occur as in 

 the ameba (Lewis, 1933, 1939) . 



The neutrophilic leucocytes are somewhat larger than the 

 lymphocytes and have the same sort of ameboid locomotion. The 

 anterior pseudopods are more changeable and the tail bud shorter. 

 A constriction ring develops at the base of the advancing pseudo- 

 pod which, like the one on the lymphocyte, does not move forward. 

 The endoplasm contains numerous granules which stream forward 

 into the advancing pseudopod. It is quite evident that contraction 

 and solation of the gel layer posterior to the constriction ring con- 

 tinues until all but the tail bud is carried forward in the endoplasm 

 and built up in front of the constriction ring. The granule-free 

 gel layer is very thin. It has not been possible to see either the 

 solation at the posterior end or the gelation anterior to the constric- 

 tion ring. The presence of the constriction ring, however, is the 

 key to the idea that they as well as other species of white blood 

 cells have the ameboid type of locomotion. 



Both the lymphocyte and the neutrophile move much more rap- 

 idly than a fibroblast and appear to have a less viscous endoplasm 

 than the latter. Fibroblasts and sarcoma cells move very slowly. 

 One cannot detect in the course of a few minutes any forward 

 movement. Such cells, however, occasionally develop a constriction 

 ring which indents and distorts the nucleus. These rings, like fixed 

 granules of the ameba and the constriction rings of the lymphocyte 

 do not move forward, yet the nucleus is slowly pushed through 

 them in the course of four or five hours, presumably by contraction 

 of the posterior part of the cell which pushes the nucleus and 

 rather viscous endoplasm very slowly forward. It seems quite 

 probable that fibroblasts, and sarcoma cells which are derived from 

 them, have a very slow ameboid locomotion because the endoplasm 

 is almost as viscous as the gel layer. 



Ruffle pseudopodia and undulating membrane common on white 

 blood cells, macrophages, connective tissue cells, and sarcoma cells 

 consist of exceedingly thin sheets of hyaline protoplasm. They often 

 extend into the fluid medium of cultures and are always slowly 

 bending back and forth like the ruffles on a dress in a slight breeze. 

 They probably have an outer thin gel layer and a central somewhat 

 less viscous endoplasm. Slight local changes in the viscosity of the 



