John Perdue Gray (Aug 6, 1825 - Nov 29, 1886) was an American psychiatrist at the forefront of biological psychiatric theory during the 19th century. Gray was the superintendent of Utica State Hospital in New York and was also the editor of the American Journal of Insanity, the precursor to the American Journal of Psychology. Gray believed that insanity was always due to physical causes and that the mentally ill should be treated as physically ill.
Gray, John P. General Paresis, or Incomplete Progressive Paralysis. Albany, NY: Van Benthuysen, 1866.
Gray, John P. Insanity, its Dependence on Physical Disease. Utica, NY: Roberts, 1871. https://archive.org/details/insanityitsdepen00gray
Gray, John P. Insanity: its Frequency and Some of its Preventable Causes. Utica, NY, 1886.
Gray, John P. The United States vs. Charles J. Guiteau, Indicted for Murder of James A. Garfield, Twentieth President of the United States. Opinion of … on the Sanity of the Prisoner. Washington, 1882.