If you look in the links bar off to the right, you’ll find a new link to a gallery of mad science pulp art at Silverghost, which contains some very fine examples of the genre.

Like this, for instance.  Mad scientist, pretty girl apparently dissolving in a vat.  Could this be an early example of the Apsinthion Protocol meme?

Chasing the provenance on this one was a little tricky.  It seems to have been the cover art for a pulp magazine called Fantastic Adventures, which according to Wikipedia was published between 1939 and 1953.

I was able to find a scan of the cover online, but it’s a thumbnail so unfortunately I can’s read the date.  However cross-checking the novel The Involuntary Immortals on Rog Phillips’s entry in the Internet Science Fiction Database would seem to place the publication date in 1949.  I would welcome additional provenance in the comments.