In old-time pregnancy tests, did the rabbit really die?
I just hit 40 and still have an unanswered question from my teens that has always bothered me. Aerosmith in "Sweet Emotion" sings about being accused of impregnating a girl. At the end of the verse they sing, "can't catch me 'cause the rabbit done died," referring to a pregnancy test. Arguments start over just what this test entails. Most say the bunny will die, but can't agree as to why. Some say the rabbit will always die because they kill it before they take its blood (which seems pretty dumb). Some say they inject it with some fluid taken from the woman and it dies a horrible, convulsive death. And some say they have to dissect the rabbit after it has been injected. This was before those home test kits, but wasn't there a better way?
The rabbit test isn't used much anymore, and feeling a need to conserve the neurons I hadn't studied the matter too closely. Frankly I had the idea that the death of the rabbit signified a positive result; i.e., you were pregnant. Always struck me as weird. What were you supposed to do, cheer for the rabbit to die?
Turns out I was misinformed. The bunny died regardless of the outcome of the test — not happy news, but at least we get away from the equation of one more human = one less rabbit. I learn this from my buddy Clark, an M.D. who heads the surgical division of the Straight Dope Science Advisory Board. Clark, by the way, scoffed at the idea that one could obtain accurate scientific knowledge from Aerosmith tunes. He preferred M*A*S*H (the TV show), which had a relevant episode.
Here's the background. In the rabbit test and other pregnancy "bioassays" (animal-based tests), you injected some of the woman's urine into the critter and observed what happened. During early pregnancy the urine contains an elevated level of hCG (human chorionic gonadotropin), which triggers "corpora hemorrhagica" (bulging masses) in the female rabbit's ovaries. Grim though these sound, the real problem for the rabbit was that you couldn't see them if the rabbit was in the way. The accepted procedure was to kill the animal and dissect it. The difference in the M*A*S*H episode — I believe they were trying to determine whether Hot Lips was pregnant — was that the sacrificial bunny belonged to Radar, so the softhearted doctors agreed to anesthetize it and later sew it up.
Other pregnancy bioassays didn't involve killing the test animal. But they all seemed to involve squeezing pee out of a frog, sticking a tube up a toad's behind, or performing some other grotty procedure that made you understand why doctors charge so much. When cheap, fast tests without animals were developed, it wasn't just pregnant women and rabbits who heaved a sigh of relief.