An experimental inquiry into the central source of preganglionic fibers to the chick ciliary ganglion

Degenerative changes in the entire third nerve nucleus were studied following selective removal of the ciliary ganglion, usually of the right side, in day-old chicks. The operated animals were allowed to survive three, six, nine, and twelve days after ciliary ganglionectomy. Retrogarde degenerative changes proceed rapidly between three and nine days post-operatively, and are strictly limited to the ipsilateral accessory oculomotor nucleus. The changes are at first observed in the medial division of the accessory oculomotor nucleus, followed by the lateral division of the accessory oculomotor nucleus. By nine days following the operation, both the divisions of the accessory oculomotor nucleus are virtually depleted of almost all neurons. The other components of the oculomotor complex were not affected at any stage by ciliary ganglionectomy. These observations provide conclusive evidence that the accessory oculomotor nucleus is indeed the avian homologue of the Edinger-Westphal nucleus.