Visual pathways concerned in gonadal stimulation in ferrets

Anoestrous ferrets become reproductively active in winter if the number of hours of light to which they are exposed daily is prolonged by artificial illumination (Bissonnette 1932). This response, which has also been demonstrated in wild mice and various species of birds, cannot be elicited after hypophysectomy (Hill and Parkes 1933), while it is much impaired after division of the optic nerves (Bissonnette 1935a, b, 1936). It is therefore concluded by most worker that activation of the gonads in such experiments is primarily dependend on retinal stimulation (Marshall and Bowden 1934), and on the effects which such stimulation has upon the pituitary. The present paper is a record of a series of experiments which were designed to discover possible nervous pathways through which retinal stimulation may affect the pituitary.