Dual innervation of the pineal of the fowl, Gallus domesticus.

Abstract

THE occurrence of nerve fibres in the pineal of the fowl was once thought unlikely1, but it is now accepted that many fine neurites are present2,3. Although myelinated fibres have been observed4, most are unmyelinated and many of them contain the cored vesicles4,5 which are characteristic of adrenergic nerves. In mammals innervation is probably exclusively sympathetic from cells originating in the superior cervical ganglion3, but sympathectomy experiments have suggested that different mechanisms of stimulation may exist in the chicken6.