Note 18 — Chapter I · INTRODUCTORY
Reading edition
In a famous lecture (Conservation of Forces applied to Organic Nature, Proc. Roy. Instit., April 12, 1861), Helmholtz laid it down, as “the fundamental principle of physiology,” that “There may be other agents acting in the living body than those agents which act in the inorganic world; but those forces, as far as they cause chemical and mechanical influence in the body, must be quite of the same character as inorganic forces: in this at least, that their effects must be ruled by necessity, and must always be the same when acting in the same conditions; and so there cannot exist any arbitrary choice in the direction of their actions.” It would follow from this, that, like the other “physical” forces, they must be subject to mathematical analysis and deduction. Cf. also Dr T. Young’s Croonian Lecture On the Heart and Arteries, Phil. Trans. 1809, p. 1; Coll. Works, I, 511.