The Use of the Friedman Test for Pregnancy with Chimpanzees *

Since Friedman's discovery5 in 1929 that urine from pregnant women would induce ovulation when injected into young female rabbits, there have been several attempts to use the test with various other mammals. These are summarized by Snyder and Wislocki8 and by Schultz and Snyder.7 Reports of experimental and clinical observations on the use of the Friedman test for diagnosis of pregnancy are very numerous. Its reliability for human pregnancy is high, but until recently it was believed generally to be without value when used with other primates. Hamlett,' however, has shown that urine from the pregnant macaque will produce ovulation in the rabbit if the test specimen is obtained very early in pregnancy. On days 19 to 25 following ovulation Hamlett obtained positive reactions in eight of ten cases. Six years ago, with the number of pregnancies in the colony increasing, these laboratories sought to discover some objective test of diagnostic value which could be used with chimpanzees during early pregnancy. Zuckerman,10 using urine specimens from subjects in these laboratories, obtained results which led him to conclude that the Aschheim-Zondek reaction is a test of pregnancy in chimpanzees. The present series of observations with the Friedman test was started in 1935 with four subjects, two of which had passed the 150th day of pregnancy. Most of the results were negative. Some months later Dr. Carl G. Hartman gave us a suggestion, based upon results Hamlett was getting then with monkeys, which seemed to provide a good explanation for our early negative reactions. Since the Friedman test is positive for almost the entire period of gestation in man and for a few days only in the monkey, then perhaps the chimpanzee would complete a phylogenetic series by showing "positives" throughout some intermediate period-perhaps up to 100