Julius Robert von Mayer (November 25, 1814 - March 20, 1878) was a German physician and physicist and one of the founders of thermodynamics. He is best known for enunciating in 1841 one of the original statements of the conservation of energy or what is now known as one of the first versions of the first law of thermodynamics, namely that "energy can be neither created nor destroyed". In 1842, Mayer described the vital chemical process now referred to as oxidation as the primary source of energy for any living creature. Mayer was aware of the importance of his discovery, but contemporary physicists rejected his principle of conservation of energy, and Hermann von Helmholtz and James Prescott Joule viewed his ideas with hostility. His achievements were overlooked and priority for the discovery of the mechanical equivalent of heat was attributed to James Joule in the following year. In 1848 two of his children died rapidly in succession, and Mayer's mental health deteriorated. He attempted suicide in 1850, was committed to a mental institution, but eventually released. His scientific fame had grown and he received a late appreciation of his achievements, although perhaps at a stage where he was no longer able to enjoy it. He continued to work vigorously as a physician until his death in 1878 at the age of 63.