Answers are grounded in this paper and cite their sources.
The circadian rhythm of pineal serotonin and the influence of light on that rhythm have been confirmed. Removal of the Harderian gland abolishes the response to light in blinded animals, which suggests that this gland may act as the extraretinal transducer involved in the persistence of the pineal rhythm in blinded suckling rats.
No takes yet. Share an insight, caveat, or question.
Wetterberg et al. (1970) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: