| Popis: |
THE fact that lengthening the hours of light during the winter increases the egg production of fowls at that season has been known for many years. The literature has been fully covered by Dobie, Carver and Roberts (1946). The theory that the increase of gonadal activity may be caused by the effect of light on the endocrine system has been reviewed by Rowan (1938). Rider (1938) has shown that fowls need not have feed available during the hours when artificial light is provided; this was confirmed by Callenbach, Nichols and Murphy (1943). Fairbanks (1924) demonstrated that the intensity of light at the surface of the fowl need not exceed one foot-candle. That red rays of light were stimulating to egg production and blue rays depressing was shown by Rider (1938). In view of the evidence, there was every reason to believe that if fowls were exposed to a dim red . . . |
