What did Hermann von Helmholtz argue in his 1847 paper “On the Conservation of Force”?

In his 1847 paper, “On the Conservation of Force,” Hermann von Helmholtz argued that vital heat—the heat produced within a living organism—must be the product of mechanical forces rather than a mysterious "vital force".1

He reasoned that if vital heat were not the sum of chemical reactions within the body, it would imply the existence of a source not subject to physical laws, which would theoretically allow for the creation of a perpetual motion machine. Because physics had already rejected the possibility of such machines, Helmholtz concluded that vital heat must follow ordinary physical laws.1

By generalizing these results, he stated that all heat is related to ordinary forces and that force itself can never be destroyed. This work provided one of the first and clearest statements of the principle of the conservation of energy, marking a significant milestone in both the history of physics and physiology by allowing scientists to perform material and energy balances on organic systems.12