Page 125 - Visions of the Future Chemistry and Life Science

114 M. C. H. VAN DER MEULEN AND P. J. PRENDERGAST

(a)
(b) (c)

Figure 7.1. Early diagrams showing the relationship between stresses created by
forces on bones and the internal architecture of the skeleton: (a) Culmann’s
calculation of the stress trajectories in a crane, (b) Wolff’s drawing of the trabecular
orientation in the upper part of the femur, and (c) a photograph of the cross-section
of the upper part of the femur.

strength. In discussing heritable and acquired traits in On the origin of
species, Charles Darwin noted that flying wild ducks have proportionally
larger wing bones and smaller leg bones than their nonflying domestic rel-
atives. Many natural philosophers of the nineteenth century used mechan-
ical principles to explain bone geometry. In 1892 Julius Wolff studied many
pathologically healed bones and concluded that bone tissue is distributed
within the organ in ways to best resist mechanical forces. A famous
exchange between the Swiss engineer Karl Culmann and his colleague
Hermann von Meyer is considered the defining ‘eureka’ episode of modern
biomechanics. The internal architecture of a femur was being demon-
strated by von Meyer, and Culmann, who developed the methods of
graphic statics, exclaimed, ‘That’s my crane’ (Figure 7.1). These concepts
were further developed and generalised by D’Arcy Thompson in his
influential work On growth and form in 1917. The mechanism of bone
adaptation was first addressed by the German embryologist Wilhelm Roux
in 1895, who proposed the controversial hypothesis that bone cells
compete for a functional stimulus, à la Darwin, and engage in a struggle
for survival that leads to Selbstgestaltung (self-organisation).
Roux and his contemporaries were not able to advance much beyond