34. The Menstrual Cycle of the Primates.—Part IV. Observations on the Lactation Period



  • 1A Pig-tailed Macaque (Macaca nemestrina) gave birth to a female baby after 171 days' gestation. The first menstruation occurred 216 days after parturition. There had been no sexual-skin swelling in the interval.
  • 2A nursing Common Macaque (Macaca irus, M. 61) was killed approximately 114 days after parturition. She was wasted, and post-mortem examination revealed worm-infestation of the intestines. Her mammary glands, though they still showed marked lactation hypertrophy, were not secreting milk at the time of death. Her ovaries were inactive, and showed a large number of atretic follicles. Her uterine mucous membrane was low, with short and straight glands, and showed signs indicating that involution was still proceeding at the time of her death.
  • 3A nursing Langur (Pithecus cristata, M. 46) was shot in Borneo at a time that is estimated to have been at least two months after parturition. The ovaries, though small and contracted, contained medium-sized follicles, the largest having an average diameter of 2·2 mm. There was no sign of a corpus luteum. Each ovary contained a large corpus candicans. The condition of her uterus was much the same as that of the nursing Common Macaque.
  • 4Four nursing Chacma Baboons (Papio porcarius, M. 20, 21, 28, 37) were shot in South Africa, two at a time estimated to have been two months, a third four months, and the fourth at an unknown time, after parturition. The reproductive organs of all four were in practically the same condition, and showed no signs of recent cyclical activity. The ovaries were small, containing no signs of copora lutea, but only resting follicles. The uteri were small and inactive, with low endometria, and showed signs indicating that involution was still proceeding at the time of death.
  • 5These data, as well as sexual-skin observations recorded in Part I. of this series of papers, indicate that sub-human primates experience a period of uterine and ovarian inactivity after parturition. This fact is of importance in discussions relating to periods of reproductive inactivity in monkeys, e. g., alleged breeding-and non-breeding seasons.