584 



Hermaphroditism in the Monkey 



menstrual cycle of the rhesus monkey is normally about twenty-eight days 

 long and the duration of gestation six lunar months (168 days). In our labora- 

 tory the female animal is placed with the male for only forty-eight hours in a 

 given cycle, so that the day of conception can be reckoned without great error. 

 However, the early detection of pregnancy in the monkey presents greater 

 difficulty than in the human because there is neither a "missed menstruation" 

 to suggest that conception has taken place, nor a pregnancy test to confirm it. 

 A menstrual cycle slightly longer than usual and a more prolonged bleeding 



TABLE 1 

 Hormone Administration to Mother Monkeys and Description of Fetuses 



at the time of the expected menstruation (placental sign) are two bits of evi- 

 dence, neither one invariably present, which may indicate pregnancy. If rectal 

 palpation then discloses that the uterus is gradually changing in consistency 

 and shape, the diagnosis of pregnancy becomes possible sometime between the 

 twenty-fifth and thirty-fifth day after conception. 



Experimental. Nine monkeys as they became pregnant were selected from 

 the breeding colony. Most of these were parous animals which had delivered 

 living young the preceding year. Six of these received a series of hormone in- 

 jections beginning at various times after conception; the pregnancies of the 

 other three were allowed to continue without treatment. 



Because of the relatively great length of pregnancy in the monkey, it was 

 possible to save both time and the hormone by removing all fetuses as nearly 

 as possible on the one hundredth day of gestation. As control material, a nor- 

 mal female fetus was removed from monkey 72 on the one hundred second day, 

 and a normal male fetus from monkey 94 on the ninety-sixth day. For a com- 

 parative study, a younger stage in normal male development was sought and a 

 seventy-four-day fetus removed from monkey 29 completed the control series. 



