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This is the back cover of Amazing Stories for January 1940, a painting by artist Paul Maxwell. The cover illustrates an article by Henry Gade. The ISFDB entry for the issue is here. I found the back cover itself at Pulp Covers. You can read and download the whole issue at the Internet Archive.
Unfortunately you’ll wake up in the year 2000 without nipples…
By 2000 science will have figured out how to regrow them.