I vectorized this with Inkscape from a public domain line drawing I found on Wikipedia by a user named "Rama". I also have posted this SVG file to the Wikimedia Commons:
http://commons.wikimedia.org/wiki/Image:Caduceus.svg

Original drawing:
http://commons.wikimedia.org/wiki/Image:Caduceus_large.jpg

Tags: media, clip_art, externalsource, how_i_did_it, public_domain, image, svg, caduceus, medical, doctor, symbol, greek, line_art, icon, caduceus, medical, doctor, symbol, greek, line_art, icon