The test was developed in 1931 by Maurice Friedman and Maxwell Edward Lapham[1] at the University of Pennsylvania.
The hormone human chorionic gonadotropin (hCG) is produced during pregnancy and can be found in a pregnant woman's urine and blood; it indicates the presence of an implanted fertilized egg.
[2] When urine from a woman in the early months of pregnancy was injected into immature female mice, their ovaries would enlarge and show follicular maturation.
[3] Friedman and Lapham's test was essentially identical, but replaced the mouse with a rabbit.
A few days after the injection, the animal would be dissected and the size of her ovaries examined.