It has been my privilege and pleasure during the past half century to
participate in the unfolding of present-day concepts of the mammalian
female reproductive cycles. When the studies recorded here began in the
late 1930s it was already established that cyclic ovarian function is
governed by gonadotropic secretions from the anterior pituitary gland,
the "conductor of the endrocrine orchestra," and that in turn this
activity is importantly dependent in some way upon secretion of estro-
gens and progesterone by the ovaries. Although a role of the nervous
system was recognized for the reflex-like induction of ovulation in
rabbits and cats and the in- duction of pseudopregnancy in rats and
mice, and although there was even some evidence of neural participation
in ovulation in rats, a major central neural role in the female cycle of
most species was not apparent. Gonadotropic fractions of pitui- tary
extracts having distinct follicle-stimulating and luteinizing activities
in test ani- mals had been obtained, and these respective effects had
been fairly well charac- terized. Prolactin was well known for its
lactogenic activity, but its luteotropic role in rats and mice had yet
to be revealed. The molecular structure of the several estro- gens and
progesterone was known, and they were readily available as synthetic
pro- ducts. The broad concept of ovarian-pituitary reciprocity appeared
to be an accept- able explanation of the female cycle, with the ovary in
control through the rhythmic rise and fall in secretion of follicular
estrogen.