Optimal Mating Time for Pregnancy in the Monkey

THE RHESUS MONKEY (Macaca mulatta) has become the laboratory animal of choice for study in the physiology of reproduction because of the twenty-eight day menstrual cycle, an extended pregnancy (circa 168 days), and the fact that the genital tract, anatomically, is so like a miniature replica of the human. The rhesus baby, too, is born a helpless suckling. It is the purpose of this paper first to present in summary the results of five years of monkey breeding during which period there was in use a rigorously standardized plan for mating at a particular time in the menstrual cycle and for a limited time only. Second, there will be contrasted with these results the outcome of the following year of breeding in which one change was made in the routine; viz., the time of mating was displaced six days later in the menstrual cycle.