Am doing some medical department study and am aware that surgeons held miltary ranks. How was the rank of the Surgeon determined? Was the Rank according to the experience he had, or was it relative to the level of his responcibilities?

For example was a surgeon given the rank of Lieutenant? or Captain? if he was a Regimental Surgeon? Would he have been a Captain? or a Major? if he were in command of a hospital, or a Brigade surgeon? I know that the Trans-Mississippi Department chief medical Officer was a Colonel.

Does anyone have any insight as to how the military rank of Surgeons was structured.