Hi Cornell,
In case you can't find out who the cartoonist is, you can always add a disclaimer explaining that you'll be glad to give proper credit to the copyright if someone can help identify the cartoonist.
I've seen unknown copyright issues on a variety of writings etc. and that type of disclaimer helps protects the unknown content on your web site.
If it happens to be from a Cartoon episode...
You may be able to Find it...
Some Great Fun & Nostalgia.
Big Cartoon DataBase...
Huge Cartoon episode Search engine/resource...
http://www.bcdb.com/bcdb/page.cgi
http://www.bcdb.com/bcdb/search.cgi
Phil