THE INNERVATION OF THE AVIAN HYPOPHYSIS

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Abstract
Considerable disagreement exists as to the question of whether nerve fibers of the hypothalamico-hypophyseal fasciculus innervate the pars distalis of any sp. The bird hypophysis is particularly suitable for such study in that the pars distalis is Completely separated from the processus infundibuli except for a small strand of the pars tuberalis which extends from the pars distalis to envelop the infundibular stalk. Ag preps. of the diencephalon and hypophysis reveal a prominent hypothalamico-hypophyseal fasciculus. Fibers of this fasciculus, as nearly as can be traced in pyridine-silver preparations, can be followed from a region dorsal to the optic chiasma and from a nucleus in the lower wall of the third ventricle. Fibers of other origins may be contained in the hypothalamico-hypophyseal system. The majority of the hypothalamico-hypophyseal fibers terminate in the processus infundibuli; however, some fibers pass into the pars tuberalis. Other fibers not contained in the hypothalamico-hypophyseal fasciculus and probably of autonomic origin accompany vascular channels into the pars tuberalis but do not pass into the pars distalis. No nerve, fibers could be traced from the hypothalamico-hypophyseal fasciculus, through the tuberalis into the pars distalis. Arteries adjacent to the hypophysis are accompanied by prominent nerve bundles which often possess small ganglionic masses along their course. Nerve fibers of this type could not be traced into the pars distalis.

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