My understanding of the morphine connection in the lyrics had to do with technology--the invention of the hypedermic needle--and the use of morphine as a painkiller during field surgery, vs using morphine as a "recreational drug." However, there were no laws at the time of the civil war against the use of morphine, and morphine, along with cocaine, were common ingredients in patent medicines sold at the time. This always created a sadness, for me, about the lyrics--addiction created unwittingly, along with the horror of the war itself.