Richard Kremer, The Thermodynamics of Life and Physiology, 1770-1880, 1990 In his Ph.D. thesis, Richard Kremer examined the historical relationship between physiology and thermodynamics. He showed that thermodynamics in the mid-19th century was an integral part of physiology, especially in the investigations of heat and the transformation of energy on animals. In the 1850s, Liebig, Hermann Helmholtz, and Robert Mayer conceptually had transformed the static chemical methods of Dumas and Boussingault into a thermo-”dynamic” approach. The principle of the conservation of energy as conceived by these workers, essentially “black-boxed” the physiological processes they were investigating in living organisms--that is, they measured only input (food) and output (changes in amount of heat).