VI] OF THE BOUNDARY STATE 449 



even in our simplest interpretation thereof, as a mere increase of 

 surface due to the existence and the multiphcation of cells. In the 

 chemistry of the tissues there may be substances (catalysts and 

 others) which exhibit their proper reactions even though the cells 

 containing them be disintegrated or destroyed ; but other processes, 

 oxidation itself among them, are essentially surface-actions, based 

 on.adsorption at the vast cell-surface of the tissue*. The breaking- 

 down of the cell-walls, the disintegration of cellular structure in a 

 tissue, brings about "a biochemical chaos, a medley of reactions f." 

 Cells are not merely there because the tissue has grown by their 

 multiplication; there are physico-chemical reasons, even of an 

 elementary kind, which render the morphological phenomenon of 

 the cell indispensable to physiological action. 



The physiologist deals with the surface-phenomena of the cell in 

 ways undreamed of when I began to write this book. To begin 

 with, the concept of a surface (in the old mathematical or quasi- 

 mathematical sense) no longer suffices to describe the boundary 

 conditions of even a "naked" protoplasmic cell. As Rayleigh 

 foretold, and as Irving Langmuir has proved, the "boundary-state" 

 consists of a layer of complex molecules, each one a long array of 

 atoms, all set side by side in an orderly and uniform way. There 

 is not merely a boundary-surface between two phases (as the older 

 colloid chemistry supposed) but a boundary-layer, which itself 

 constitutes a third phase, or interphase, and which part of the 

 surface-energy has gone to the making of. 



Surface-energy plays a leading part in modern theories of muscular 

 contraction, and has indeed done so ever since FitzGerald and 

 d'Arsonval indicated a connection between them some sixty years 

 or more agof. It plays its part handsomely (we may be sure) in the 

 electric pile of the Torpedo, where two miUion tiny discs present a 



* Many surface-active substances are known to be among the most active 

 pharmacologically; cf. Michaelis and Rona, Physikal. Chemie, 1930. 



t A. V. Hill, Proc. R.S. (B), cm, p. 138^; cf. also M. Penrose and J. H. Quastel, 

 on Cell structure and cell activity, ibid, cvii, p. 168. 



X Cf. G. F. FitzGerald, On the theory of muscular contraction, Brit. Ass. Rep. 

 1878; also in Scientific Writings, ed. Larmor, 1902, pp. 34, 75. A. d'Arsonval, 

 Relations entre I'electricite animale et la tension superficielle, C.R. cvi, p. 1740, 

 1888; A. Imbert, Le mecanisme de la contraction musculaire, deduit de la 

 consideration des forces de tension superficielle. Arch, de Phys. (5), ix, pp. 289-301, 

 1897; A. J. Ewart, Protoplasmic Streami-ng in Plants, Oxford, 1903, pp. 112-119. 



