278 Cf. Pauli, Allgemeine physikalische Chemie d. Zellen u. Gewebe, in Asher-Spiroãs Ergebnisse der Physiologie, 1912; Przibram, VitalitûÊt, 1913, p. 6.
279 The surface-tension theory of protoplasmic movement has been denied by many. Cf. (e.g.), Jennings, H. S., Contributions to the Study of the Behaviour of the Lower Organisms, Carnegie Inst. 1904, pp. 130ã230; Dellinger, O. P., Locomotion of Amoebae, etc. Journ. Exp. Zool. III, pp. 337ã357, 1906; also various papers by Max Heidenhain, in Anatom. Hefte (Merkel und Bonnet), etc.
280 These various movements of a liquid surface, and other still more striking movements such as those of a piece of camphor floating on water, were at one time ascribed by certain physicists to a peculiar force, sui generis, the force ûˋpipolique of Dutrochet: until van der Mensbrugghe shewed that differences of surface tension were enough to account for this whole series of phenomena (Sur la tension superficielle des liquides considûˋrûˋe au point de vue de certains mouvements observûˋs û leur surface, Mûˋm. Cour. Acad. de Belgique, XXXIV, 1869; cf. Plateau, p. 283).
281 Cf. infra, p. 306.
282 Cf. p. 32.
283 Or, more strictly speaking, unless its thickness be less than twice the range of the molecular forces.
284 It follows that the tension, depending only on the surface-conditions, is independent of the thickness of the film.
285 This simple but immensely important formula is due to Laplace (Mûˋcanique Cûˋleste, Bk. x. suppl. Thûˋorie de lãaction capillaire, 1806).