EFFECT OF LIGHT ON SEXUAL MATURATION, ESTROUS CYCLES, AND ANTERIOR PITUITARY OF THE RAT1

THE FACT that light stimulates many vertebrates, hastening the onset of the breeding season or inducing precocious sexual maturity, has already been es-il_ tablished. It has also been shown that this stimulation of the gonads and accessories is mediated through the anterior pituitary. For a review of the subject see Bissonette (1). The effect of light on a polyestrous mammal was investigated by Hemmingsen and Krarup (2), who found that the normal diurnal variations associated with estrus in the rat were reversed when the day-night rhythm of light was artificially shifted. They further reported a prolonged cornification of the vagina in rats kept under continuous light. Browman (3), confirmed the effect of light on the vaginal smear and also found no significant change in the age at which vaginal introitus occurred.