According to the 1863 General Regulations For the Military Forces issued by the Adjutant-General's Office, the Surgeon General was "charged with the administrative details of the Medical department and general oversight and charge of all the officers belonging to it." Furthermore, when appointing or promoting any person in the medical staff, the Surgeon-General was directed to "rigidly scan the pretensions of such person, taking into consideration his physical qualifications and moral habits, as well as his professional acquirements and education."
From the description of Incoming correspondence received from medical officers of New York State Volunteer units, 1861-1866. (New York State Archives). WorldCat record id: 122487252