Showing papers by "Robert M. Yerkes published in 1943"

Factors influencing the reproductive cycle in the chimpanzee; the period of adolescent sterility and related problems

Abstract: DURING a comparison of the reproductive cycles displayed by a group of ovariectomized chimpanzees with those shown prior to the operations (Young, Fish and Dorfman, 1942), our attention was attracted to certain changes and fluctuations in the character of the cycles which have occurred in every adult subject in the Orange Park colony. These changes and fluctuations were found to be associated most definitely and conspicuously with age, with pregnancy and with the season of the year. Counterparts are seen in other primates, including man, but almost without exception the effects which have been described are stated in terms of the entire reproductive cycle. With the chimpanzee it has been possible to go much farther since the sexual cycle in this species is divided into four easily identified parts corresponding to a) a short initial phase of follicular inactivity, b) a phase of follicular activity, c) a luteal phase and d) menstruation.