Techniques & Technologies

Frogs (Xenopus laevis)

Two Xenopus laevis in a tank.

In 1930, British zoologist Lancelot Hogben (1895-1975) discovered an extract from a sheep’s gland caused frogs of the species Xenopus laevis to produce eggs. The extract contained a hormone that stimulates this ovulation. A similar hormone is present in the urine of pregnant women, and South African researchers Hillel Abbe Shapiro and Harry Zwarenstein used this phenomenon to turn the frog into a pregnancy test. The test worked by injecting a Xenopus frog with a woman’s urine. The frog was then put in a jar with a little water. If eggs were in the water a day later it meant the woman was pregnant.

After ten years of tests, Shapiro and Zwarenstein reported the diagnosis was correct in over 98% of cases. A GP wrote to them to praise the new method: ‘Thank you for your report on the pregnancy test on Mrs. X. You may be interested to know that of one GP of many years’ standing, one specialist gynaecologist and one frog, only the frog was correct.’