In my extra-Mudcat searches yesterday, I discovered a scholarly site claiming that St James indeed is rooted in the The Unfortunate Rake. Likewise, Streets of Laredo - and others.
St James Infirmary certainly has a New Orleans bluesy style, it seems to me - lyrically and musically. It makes sense that the basic story line of The Unfortunate Rake could have evolved into St James.
Where can I find a midi with the melody of The Unfortunate Rake? Thanks all, for the input.