V] OF SURFACE ACTION 359 



tions, but we find ample room to trace the operation of the same 

 cause in producing, under conditions of rest and equiUbrium, certain 

 definite and inevitable forms. 



It is of great importance to observe that the living cell is one 

 of those cases where the phenomena of surface-tension are by no 

 means limited to the outer surface; for within the heterogeneous 

 emulsion of the cell, between the protoplasm and its nuclear and 

 other contents, and in the "alveolar network" of the cytoplasm 

 itself (so far as that alveolar structure is actually present in life), 

 we have a multitude of interior surfaces; and, especially among 

 plants, we may have large internal "interfacial contacts" between 

 the protoplasm and its included granules, or its vacuoles filled with 

 the "cell-sap." Here we have a great field for surface-action; and 

 so long ago as 1865, Nageli and Schwendener shewed that the 

 streaming currents of plant cells might be plausibly explained by 

 this phenomenon. Even ten years earlier, Weber had remarked 

 upon the resemblance between the protoplasmic streamings and 

 the currents to be observed in certain inanimate drops for which 

 no cause but capillarity could be assigned*. What sort of chemical 

 changes lead up to, or go hand in hand with, the variations of 

 surface-tension in a hving cell, is a vastly important question. It 

 is hardly one for us to deal with ; but this at least is clear, that the 

 phenomenon is more complicated than its first investigators, such 

 as BUtschli and Quincke, ever took it to be. For the lowered 

 surface-tension which leads, say, to the throwing out of a pseudo- 

 podium, is accompanied first by local acidity, then by local 

 adsorption of proteins, lastly and consequently by gelation; and 

 this last is tantamount to the formation of "ectoplasm" — a step 

 in the direction of encystmentf. 



The elementary case of Amoeba is none the less a complicated one. 

 The "amoeboid" form is the very negation of rest or of equihbrium; 



* Poggendorff's Annalen, xciv, pp. 447-459, 1855. Cf. Strethill Wright, Phil. 

 Mag. Feb. 1860; Journ.Anat. and Physiol, i, p. 337, 1867. 



t Cf. C, J. Pantin, Journ. Mar. Biol. Assoc, xiii, p. 24, 1923; Journ. Exp. Biol. 

 1923 and 1926; S. 0. Mast, Jo^lrn. Morph. xli, p. 347, 1926; and 0. W. Tiegs, 

 Surface tension and the theory of protoplasmic movement, Protoplasma, iv, 

 pp. 88-139, 1928. See also (int. al.) N. K. Adam, Physics and Chemistry of Surfaces, 

 1930; also Discussion on colloid science applied to biology (passim), Trans. Faraday 

 Soc. XXVI, pp. 663 seq., 1930. 



