The role of force or power in Liebig's physiological chemistry.

I IN THE last two decades historians of science have shown increasing interest in the emergence of the doctrine of the conservation of energy. A particular aspect of this topic has been the contribution made to nineteenth-century discussions on force and power by men working in physiology: Hermann Helmholtz (1821-1894) and Julius Robert Mayer (1814-1878) are probably the best known. The seminal paper for this topic among historians of science was T. S. Kuhn's 'Energy conservation as an example of simultaneous discovery',1 in which Kuhn identified about a dozen natural philosophers in Europe who, largely independent of one another, were developing views on forces and their interrelations which resembled and probably led up to the formal principles of the correlation of forces (as enunciated especially by William Robert Grove (1811-1896)2) and the conservation of energy (as enunciated by Hermann Helmholtz in 18473). Of those dozen natural philosophers, Kuhn identified three who were working in physiology Helmholtz, Mayer, and Liebig (1803-1873).4 This paper will examine Liebig's ideas on force or power in the light of Kuhn's and later scholars' studies. However, I wish to make three preliminary comments before examining Liebig's work in detail. First, although some scholars have discussed Liebig's interest in dynamics since Kuhn's paper and in greater detail than he did, they have usually addressed themselves