JAMA. 1948;138(2):121-125. doi:10.1001/jama.1948.02900020017006.
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In March 1947 I1 published the first results of a new biologic pregnancy test, in which male toads, "Bufo arenarum Hensel," were used as the reacting animals.

One year has elapsed since the first experiments were made, in January 1947, and it is believed useful and desirable to summarize the information obtained since then from the accumulated statistics and the many papers published on the subject.

The basis of this reaction is the phenomenon which occurs in the testicle of the adult male toad as a direct result of gonadotropic stimulation. The positivity or negativity of the reaction to the test is produced by the presence or absence of spermatozoa in a drop of toad's urine, collected by means of a pipet and observed microscopically within a few hours following the subcutaneous injection of 10 cc. of urine from the woman suspected to be pregnant.



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