Male British Toad as a Pregnancy Test Animal

The One‐hour Pregnancy Test, Using the Male British Toad

“…The technique of injection of toads, and of collection and examination of their cloacal urine has already been described (Frazer and Wohlzogen, 1950;Frazer, 1950). Toads were injected with 4 i.u.…”

“…It has been shown (Frazer and Wohlzogen, 1950) that the accuracy of the test may be as high as 99.9 per cent, while in only 16 per cent of toads given pregnancy urine was there a failure to respond in 4 hours or less. Many species of toads have now been used for this, including the British one (Bufo bufo).…”

The Comparative Sensitivity of the Male Toad Pregnancy Test and the Friedman Test

“…If a laboratory is considering replacing the Friedman by a toad test, the question must be considered of the comparative advantages of the Galli Mainini test, using the English male toad, and the-Hogben test with the female African toad, Xenopus laevis, which is used in the larger pregnancy diagnostic centres at Edinburgh and Watford (Schwabacher, 1950). In either case a concentration technique will be necessary in some cases, and, though the male Bufo is somewhat more sensitive than the female Xenopus, requiring according to Frazer and Wohlzogen (1950) about 8 i.u. chorionic gonadotrophin in 1 or 2 ml.…”

“…Schwabacher (1950) allows at least one month's interval between tests with Xenopus. Frazer and Wohlzogen (1950) allow an interval of one week with Bufo, and reject the animal after four injections. But it was found in this laboratory that, though a toad injected at weekly intervals with positive urine may give a weak or negative reaction after four or more weeks, yet, if the interval between injections be lengthened to a month, the same toad will regain the ability to give a strong positive reaction, so that with monthly injections Bufo can, like Xenopus, be used repeatedly throughout its life.…”

“…Bufo has the advantage of speed (two to six hours as against 18 hours), and this makes it a convenient animal if a preliminary examination is carried out before concentration methods are used. Frazer and Wohlzogen (1950) state that Bufo bufo is sensitive to about 8 i.u. chorionic gonadotrophin, and that this sensitivity does not vary significantly throughout the year in animals kept in a Warmed animal house.…”