The practical value of the frog test in the diagnosis of normal and pathological pregnancy.

The laboratory diagnosis of pregnancy, initiated by the discovery of the Aschheim-Zondek reaction, remained for a long time a comparatively seldom used procedure, performed only on selected cases. The original method and its later modifications (the Friedman test, the quick hyperaemia test) need comparatively expensive test animals. Moreover, the performance of the test and reading of the results is by no means always easy and requires a highly skilled laboratory staff. One of the simpler procedures, the female Xenopus Lewis frog test, although much advocated for some time, was found to lack sensitivity and the animals were difficult to breed and maintain outside their native land. The various chemical procedures proposed lacked both sensitivity and specificity and therefore have been disappointing. A new era in this field was initiated by GalliMainini, who described the use of several species of South American male frogs for the diagnosis of pregnancy (Galli-Mainini, 1948). The procedure became universally known as the " frog test " and very favourable reports about its use were soon published in the medical press of many countries (Wiltberger and Miller, 1948; Haines, 1948; Hinglais and Hinglais, 1948; Nobili, 1948; Rabau and Szejnberg, 1949). The following is a summary of experience with this procedure during nearly 10 years of its routine use. In nature the male frogs and toads release spermatozoa after a prolonged contact with the female, which stimulates the secretion of the gonadotrophic hormone from the hypophysis. A similar effect may be obtained by injecting human chorionic gonadotrophin excreted in urine during pregnancy, or in cases of hormone-secreting neoplasms (chorionic epithelioma, hydatid mole).