The Wellcome Trust has made their collection of medical images available for use under a Creative Commons license. The Wellcome-images collection is huge. I’ve been poking around on their site and having a good old time.
I rather like this one. It is, however, unclear to me how syphilis and the lithograph relate. The image would seem to indicate that you can contract syphilis from a swimming pool (last time I checked, that’s not the case). More likely is the far more subtle implication of being cautious of picking up strange people in social settings for some sort of illicit affair.
In any case, I think this is a great lithograph.