Light and Sexual Cycles in Starlings and Ferrets

Abstract
Experimental studies on relation of daily light periods to seasonal sexual cycles indicate that these cycles, in some birds and mammals at least, are definitely conditioned by seasonal changes in duration and intensity of daily periods of exposure to light of the long-wave visible sort. In starlings, red light is more stimulating than shorter wave light. In birds the sexes appear to be about equally dependent on light changes for their sexual periodism; in the mammals investigated, [female][female] are much more completely controlled in this way than [male][male], under the experimental conditions used. Diet affects the degree of sexual reaction to light and may even act as a limiting factor, probably by deficiency of vitamins and proteins, essential for normal reproductive capacity and rhythm. Stimulation of the anterior pituitary hormone secretion via the eyes, leading to stimulation of the sex-glands and accessory organs, is suggested by the results,[long dash]possibly a neuro-humeral reaction.

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