1. A corrosion preparation of an organ (e.g., lung, liver, kidney) is obtained by injecting the system through a major artery with a coloured liquid plastic under pressure. The plastic is allowed to harden, and the soft tissue dissolved away with dilute acid. The result is an exact cast of the vascular tree of the organ.
2. Poiseuille’s law was discovered empirically, but can be derived from elementary hydrodynamic principles. See for instance G. Joos, Theoretical Physics (2nd edn), Hafner, New York, 1950, pp. 212–13.
3. Cf. D’Arcy W. Thompson, On Growth and Form (revised edition), Macmillan, New York, 1945, pp. 948–57, especially pp. 951–3.
4. See, for example, P. W. Bridgman, ‘Dimensional Analysis’ (revised edition), Yale University Press, 1956, For an attempt to apply dimensional methods directly to biological problems, the reader might consult W. R. Stahl, ‘Dimensional Analysis in Mathematical Biology I’, Bull. math. Biophys., 23 (1961) 355–76; II, ibid., 24 (1962) 81–108.
5. C. D. Murray, The Physiological Principle of Minimum Work F, Proc. nat. Acad. Sci., 12 (1926), 207–14; The Physiological Principle of Minimum Work Applied to the Angle of Branching of Arteries’, J. gen. Physiol., 9 (1926)835–41.