Poster for the 1978 film Rabbit Test, written and directed by Joan Rivers (subject of an early use of the phrase the rabbit died) and starring Billy Crystal. The poster has the image of a pregnant man (Crystal) with a woman (Rivers) pointing quizzically at his extended abdomen.
28 July 2021
You don’t hear rabbit test or the rabbit died much anymore, but if you watch old movies or television shows, you might hear the phrase the rabbit died. Simply, a rabbit test is any test that uses a rabbit as a subject animal, and more specifically it refers to a pregnancy test. The phrase the rabbit died is a slang expression meaning a positive result on a pregnancy test.
The use of rabbit test to mean a lab test using a rabbit dates to at least 1908, when it appears in and article in the Journal of Biological Chemistry in reference to a test for specific bacteria that cause putrefaction in tissue:
In ten cases where the reactions were positive, the rabbit test was made and in every instance but one (which probably failed on account of faulty manipulation) the striking phenomenon of gaseous distension of the animal was obtained.
The practice of using rabbits to test for pregnancy-related hormones in human urine was pioneered in 1931 by Maurice Friedman and Maxwell Lapham at the University of Pennsylvania. The application of rabbit test to refer specifically to a pregnancy test quickly followed. A succinct, if technical, description of the test can be found in the October 1931 issue of the American Journal of Obstetrics and Gynecology:
In describing our results with the rabbit ovulation test for pregnancy it will not be necessary to discuss the biologic basis upon which it rests, since the reader will find the subject well covered in a recent review by Aschheim (1930) dealing with the Aschheim-Zondek test, and in another by Friedman upon the rabbit test, of which he is the original proponent. It will suffice to say that the urine of pregnant human females, after about the third week, contains large quantities of substances resembling in their effects the gonad-stimulating hormones of the anterior lobe of the hypophysis. The Aschheim-Zondek test and the rabbit ovulation test are simply two different methods for obtaining evidence as to the presence or absence of the hormones in question, in a. given sample of urine. The former is performed by giving daily injections of the urine in question to immature mice; at autopsy after five days the ovaries are examined directly for signs of stimulated growth and function. The rabbit test of Friedman depends upon the fact, that rabbits, which (unlike most other mammals) do not normally mature and rupture their graafian follicles except after copulation, may be made to ovulate without copulation by giving them an intravenous injection of the gonad-stimulating hormones as found in the hypophysis and in the pregnant urine.
The phrase the rabbit died comes along much later and is based on a misconception that if the rabbit died, the pregnancy test was positive. In reality, the rabbit died either way, because the test required a necropsy to examine the animal’s ovaries. The earliest example of the slang phrase that I have found is from a syndicated gossip column of 3 July 1967 that discusses comedian Joan Rivers’s pregnancy:
JOAN RIVERS PLANS rolling right along comically until next Christmas or so th’ the baby’s due in Feb....Joan’s whole gag-bin has shifted since the rabbit died...Says her husband Edgar was a bachelor so long, when she informed him she was expecting he took the classical bachelor-attitude and shrugged, “Don’s look at me.”
The rabbit test for pregnancy is no longer performed. Present-day pregnancy tests, such as those which can be purchased over the counter at a pharmacy, operate on the same principle, testing for certain hormones, but the test is performed without using an animal, a much more humane process.
Sources:
Green’s Dictionary of Slang, 2021, s.v. rabbit, n.1.
O’Brian, Jack. “Jack O’Brian’s Voice of Broadway.” Jersey Journal (Jersey City, New Jersey), 3 July 1967, 18. Readex: America’s Historical Newspapers.
Oxford English Dictionary, third edition, June 2008 (updated June 2021), s.v. rabbit, n.1.
Rettger, Leo F. “Further Studies of Putrefaction.” Journal of Biological Chemistry, 4.1, 1908, 54. Elsevier Science Direct.
Wilson, Karl M. and George W. Corner. “The Results of the Rabbit Ovulation Test in the Diagnosis of Pregnancy.” American Journal of Obstetrics and Gynecology, 22.4, October 1931, 513. Elsevier Science Direct.
Image credit: AVCO Embassy Pictures, 1978. Fair use of a low-resolution image of a copyrighted word to illustrate the topic under discussion.