Apple #107: The Rabbit Done Died

Lots of excellent requests have been submitted so far. Keep 'em coming!

Jim F. wanted to know the origin of the phrase "the rabbit died" (or as Aerosmith put it, "the rabbit DONE died"). He knew it was related to erstwhile pregnancy tests, but wanted to know more. I had never heard this phrase but was very curious, and it turns out, the answer is quite interesting:

• In the 1920s, medical researchers discovered that, shortly after a fertilized egg implants itself in her uterine wall, a woman's body starts producing a hormone called human chorionic gonadotropin, or hCG for short. This hormone actually tells the placenta to start making progesterone so that the body doesn't reject the fertilized egg.
• In an effort to develop a test so that people could know for sure whether a woman was producing hCG, and therefore pregnant, medical researchers discovered in 1927 that if they injected female rabbits with an extract of a woman's urine that contained hCG, the rabbit's ovaries would swell within a matter of days. Basically, the rabbit's body would assume that it was pregnant, because of the woman's hCG, and start making the phantom fertilized egg feel more comfortable.
• Huzzah, researchers had a pregnancy test, a.k.a. "the rabbit test." The problem was, though, that scientists couldn't say for certain whether the rabbit's ovaries had swollen until they'd killed the rabbit and done an autopsy (this makes me regard Elmer Fudd's "Kill the wabbit" refrain in a new light).
  
• So the test rabbit always died. The proper phrase would have been something like "the rabbit's ovaries swelled up," but "the rabbit died" was more fun to say. Thus people went around saying that if the rabbit died, it meant that you were pregnant.
  
• A few years later, clinicians figured out a way to examine a rabbit's ovaries without killing the rabbit, but it was too late, people were having too much fun saying "the rabbit died."
• Pregnancy tests have continued to evolve from this basic idea of testing for hCG in a woman's urine. This is how the home test kits work today, though there's no rabbit involved.
  

Image from Wiseacre Gardens' Elmer Fudd page

Thanks, Jim F, for a great question!

Sources
Snopes urban legends reference pages, The Rabbit Test
About.com, Pregnancy/Birth, The Rabbit Died
Etymologies & Word Origins: Letter R
Am I Right - Nonsensical Song Lyrics, Aerosmith
Ricki Lewis, Ph.D, "Biotech Devices: Replacing Test Animals, Improving Diagnoses," FDA Consumer, outdated issue
The Phrase Finder, Re: The rabbit died (this site offers a slightly different explanation, citing the FDA as its source. But I can find no confirmation of this scenario at the FDA, and I found no other source that offers a similar explanation.)
"Kill the wabbit" from Looney Toones at Wavsource.com Check this site out if you can because there's lots of great stuff here.