274 IXFLAMMATIOX, liEaEyEh'ATIOX, GROWTH 



fuse about an infected catgut ligature are the leucocytes, for they are 

 most abundant in such a place.) A good illustration, also, is the 

 giant-cell formed by fusing of leucocytes about blastomyces in minute 

 abscesses in the epithelium in blastomycetic dermatitis; the epithelial 

 cells cannot flow or coalesce well because of their abundance of stitf 

 keratin and their specialized cell-wall, and hence do not participate; 

 the leucocytes are individually too small to surround the fungus cells, 

 and hence they flow about them in the abscess exactly as they will do 

 experimentally in a test-tube or in a guinea-pig's abdomen (Hektoen). 

 The method of growing tissues in vitro permits of observation of the 

 process of giant-cell formation, and establishes that, for foreign body 

 giant-cells at least, they are formed by fusion of wandering cells 

 (Lambert).*'^ The formation of giant-cells is, on this ground, but an 

 amplifieation of ameboid movement and phagocytosis. The fusing of 

 the individual cells is due to the lowering of their surface-tension by 

 the materials diffusing from the body which is to be absorbed, until 

 the surface of each cell becomes alike, when the surface tension at 

 the point where each cell is in contact becomes zero and the cytoplasm 

 runs together. 



Objections to the above Hypothesis. — Phj^sieal explanations of 

 ameboid movement seem to fit very perfectly the known facts concern- 

 ing the actions of leucocytes. There arise but a few difficulties in ap- 

 plying these laws to leucocytic action; one is the phagocytosis of 

 chemically inert bodies, such as coal particles, tattooing materials, 

 stone dust, etc. We know that amebae also may take up such inert 

 materials, although they generally refuse them, and it is believed that 

 the particles exert some local injury to the cell wall that leads to an 

 alteration in its tension. Amebee seem also sometimes to excrete a 

 sticky substance over their surfaces or over the foreign matter that is 

 to be engulfed, which excretion seems to be the result of surface 

 stimulation. Possibly " leucocytes do the same. AYe must bear in 

 mind, however, that the protoplasmic cells have much greater possi- 

 bilities for action than the "artificial ameba," since within the pro- 

 toplasm countless chemical changes are going on which must cause 

 continual alteration in surface tension ; it is (juite possible that mere 

 mechanical action may alter chemical action at the point of contact, 

 so that the injuring particle may become surrounded through local 

 liquefaction of the protoplasm. 



With the ameba, unfortunately, the explanation of all its activities 

 by purely physical analogies is apparently not so successful. Al- 

 though simple pseudopodia may be produced experimentally, and their 

 formation explained readi'v 0:1 the surface tension basis, yet we find 

 many forms of pseudopodia in the great family of amaba\ Some of 

 them are brancliing, some are fixed in extension, some have a stiff 

 elastic axis. It would also be difficult to explain cilia as produced by 



61 Anatomical Record, 1012 (G), 91. 



