Conservation and Innovation : Helmholtz's Struggle with Energy ...

"Bericht", despite the application of the principle to an analysis of some physicochemical
laws, is still largely dedicated to physiology. In the much longer
Erhaltung , instead, physiology is confined to a few lines at the end of the last
chapter. In the "Bericht" the equivalence principle based on the impossibility of
perpetual motion (but also on the opposite impossibility of destroying motion:
nothing can be created and nothing can be destroyed; a conservation of the
coefficients of correlation applies) is present together with a model for many
equivalents (the terms of the energy balance), but the equivalence principle, i.e.
the correlation principle applied in the "Bericht" is very different from the
mechanical principle of conservation of energy expressed in the Erhaltung. The
equivalence principle is much closer to the ideas of Mayer and Joule, despite the
fact that in 1846 Helmholtz did not know of their works (none of them was cited
in the "Bericht"). In fact it only asserts the numerical equivalence of the effects
involved and does not imply the assumption of central Newtonian forces and that
every effect must have a mechanical interpretation in terms of potential and
kinetic energy 62. A final relevant point is that in the "Bericht" Helmholtz did not
discuss the specific determinations of the mechanical equivalent of heat, despite
his acceptance of the mechanical theory.
In 1847 Helmholtz, while writing the Erhaltung, worked out a sixth
paper 63 again dedicated to physiological problems, later to be reprinted in the
"Physiologie" section of his collected papers..
Here Helmholtz finally tried to link the problem of animal heat with that
of the mechanical force produced by muscle action. Relevant to his purposes was
to demonstrate that heat is produced in the muscle itself. He devised a very
sensible thermocouple which, linked to an astatic galvanometer and a magnifying
coil, could detect differences of temperature in the range of one thousandth of a
degree centigrade. Through thorough experiments on frogs' legs Helmholtz was
able to find evidence that heat is generated directly in the muscle tissue, that its
origins are due to chemical processes and that production of heat in the nerves is
negligible (and thus vital force could be disposed of on empirical grounds). The
role of this experimental research on the sources of animal heat, carried forward
together with and immediately after the writing of the Erhaltung, is very
62Thus I cannot agree with Lenoir's assertion:"the physiology of muscle action laid
before Helmholtz all the elements of conservation of energy" Lenoir Strat of Life P.211.
63 Helmholtz "Wärmeentwicklung". A detailed analysis is given in Olesko & Holmes
"Experiment" Sect 6.