PHAGOCYTOSIS 257 



cles anclTsimilar substances because thc^ leucocytes are "sticky," 

 which presumably is correct, but what constitutes the "stickiness" and 

 why it varies under the influence of scrum is not indicated. Presuma- 

 bly it represents an altered viscosity, which is known to be increased 

 by increased acid content such as niiglit be produced by local asphyxia.^* 

 The nature of mechanical stimulation of cells is explained by Ostor- 

 hout*" as a chemical reaction to rupture of semipermeable cellular 

 surfaces, and there is evidence from plant cells supporting this hy- 

 pothesis, but its applicability to animal cells has not been investigated. 

 The experiments of Schaeffer*^" seem to show that amcba exhibit 

 positive chemotaxis towards such insoluble substances as carbon parti- 

 cles and glass fragments, even at a distance, although the mechanism 

 is unexplained. Similar investigations have not been made with 

 leucocytes. 



Not only leucocytes but tissue cells are capa})le of moving and per- 

 forming phagocytosis when properly stimulated, and apparently all or 

 nearly all fixed cells may act as phagocytes under some conditions. 

 Their power of independent movement is much less than their 

 phagocytic power. Endothelial cells are particularly active in pha- 

 gocytosis, as also are the new mesodermal cells produced in inflamma- 

 tion. Apparently they obey the same laws as the leucocytes, and 

 not only take up bacteria, but also fragments of cells and tissues, 

 red corpuscles, and even intact leucocytes and other cells. Brodie''^ 

 considers that phagocytosis by endothelial cells in lymph-glands is the 

 natural end of the leucocytes, and red corpuscles seem to have a similar 

 fate. 



Phagocytosis is usually accomphshed solely by the cytoplasm of the 

 cells, the nuclei maintaining a passive role; but, according to Detre 

 and Selli,^- the phagocytosis of particles of lecithin is accomphshed by 

 the nuclei, which seem to have a specific affinity for this substance. 



Giant-cell formation may also be considered as the result of chemo- 

 taxis, the cells moving toward the attracting particle, and when the 

 particle is larger than the cells they spread out upon its surface, their 

 cytoplasm flowing together because of altered surface tension. The 

 peripheral disposition of the nuclei probably depends on the fact 

 that in ameboid motion the nucleus of the cell plays an entirely passive 

 r61e, being dragged along by the cytoplasm, and hence it is located 

 most remotely from the attracting particle. Digestion of materials 

 taken into a giant-cell seems to go on as in the individual cells that 

 compose it.®^ 



^8 See Woolley, Jour. Amer. Med. Assoc, 1914 (63), 2279. 



*' Proc. Natl. Acad. Sci., 1916 (2), 237. 



«» Biol. Bull., 1916 (31), 303. 



6' Jour, of Anat. and Phvsiol., 1901 (35), 142. 



6- Berl. klin. Woch., 1905 (42), 940. 



«3 See Faber., Jour, of Path, and Bact., 1893 (1), 349. 



