Figure 3: Effect of melatonin-filled silastic implants on the free running rhythm of locomotor and feeding activity of an intact pigeon. On day 41, eleven 1.0 em melatonin filled silastic capsules were implanted intraperitoneally and the pigeon placed back in DD (arrows). Several weeks later, the capsules were removed (arrows) and the bird was maintained in DD for the remainder of the experiment.