Law implies from the employment of a doctor contract that the doctor will diagnose and treat his patient with that degree of skill and learning which is possessed by the average member of his profession in the community in which he practices. A doctor licensed to practice is presumed to possess such skill and learning. He does not incur liability for his mistakes if he has used methods, in his diagnosis and treatment, recognized and approved by the average member of the medical profession practicing in his community. A doctor's negligence in departing from the standard of practice in his community must be established by medical testimony, except in those cases where the negligence is so grossly apparent that a layman would have no difficulty in recognizing it.
John J. Kennett, Preparation and Trial of a Medical Malpratice Case, 6 Clev.-Marshall L. Rev. 87 (1957)