This content is PDF only. Please click on the PDF icon to access.
Abstract
Albino rats were raised in cyclic lighting and subjected to either constant light inhibition of the shedding peak or a 10 hr phase advance in the lighting schedule, with lighting levels of varied intensity. All responses followed sigmoid curves of shedding vs. intensity. For constant light inhibition the curve had a shallow slope with a 50% peak at 0.85 ft-cd. Shedding after a phase shift showed a steep curve with a 50% peak at 0.3 ft-cd when animals were observed at 9:30 P. M. and a shallow slope with a 50% peak at 0.003 ft-cd when observed at 7:30 A. M. It is concluded that the mechanisms of shedding inhibition and phase shifts in the shedding rhythm differ with respect to the role of light.