Dennis --

Before the war many Southern students attended medical school in Phildelphia PA.

According to the 1860 census of DeKalb County, John M (Newton?) Flowers was 13, so he's a bit young to have been a physician during the war. He should be on the 1864 militia census. However, the 1860 census lists G. H. Flowers (perhaps an older brother?) as a physician. He's 24 on the census, so this young man may be who you have in mind.