Antoine Laurent Bayle's medical thesis, entitled "Studies on mental diseases" and defended in Paris in 1822, represented an important advance in the history of biological conceptions in psychopathology. Based on a rigorous anatomic and clinical method, Bayle presented clinical observations on six patients with chronic and progressive histories of exalted behavior and ideas of grandeur, power and ambition, a condition that eventually evolved to maniac delusions with psychomotor agitation. Simultaneously, a situation of progressive paralysis of several muscle groups set in, leading to extreme physical incapacity. In the final stage the patients showed a typically demential condition with serious physical impairment which led to death. Post-mortem examinations showed the presence, in all cases, of chronic inflammation of the cerebral meninges (chronic arachnoiditis), which Bayle held to be the biological basis of the symptoms noted. Bayle thus provided a rigorous clinical description of a typical psychopathological entity with chronic and progressive evolution, and showed its relationship to specific and objectively demonstrable cerebral damage. This discovery, first received with considerable reservation, later served as a type of paradigm for research and for the theoretical and therapeutic project for biological psychiatry that began in France during the 19th century.
General paralysis; biological psychiatry; Bayle; chronic arachnoiditis