ULTRASTRUCTURAL AND MORPHOMETRIC STUDIES ON THE PERIPHERAL COURSE OF THE VAGUS IN THE DOMESTIC-FOWL, WITH PARTICULAR REFERENCE TO THE CHOLINERGIC INNERVATION OF THE PANCREAS

Cytochemical and morphometric studies were carried out to ascertain th e peripheral course of the vagus nerve to the chicken pancreas. Nerve bundles accompanying the left gastric artery were named tentatively th e left gastric artery nerve which contained unmyelinated and myelinate d nerve fibers showing the acetylcholinesterase positive reaction. Aft er vagotomy various degenerating features were observed in both the un myelinated and myelinated nerve fibers of the left gastric artery nerv e. The ratio of unmyelinated nerve fibers to myelinated nerve fibers d ecreased significantly following vagotomy, whereas there was no signif icant difference in the total number of myelinated nerve fibers betwee n the control and vagotomized chickens. Thus, it is hypothesized that the total number of unmyelinated nerve fibers decreases significantly following vagotomy. Our studies yielded the evidence that the left gas tric artery nerve contains the unmyelinated nerve fibers derived from the vagus nerve. Moreover, the coeliac plexus showed no significant ch ange in the ratio of unmyelinated to myelinated nerve fibers nor signs of degeneration following vagotomy, although both were observed in th e nerve bundles accompanying the pancreatico-duodenal artery. It is, t herefore, concluded that a peripheral branch of the vagus nerve runs t ogether with the left gastric and the pancreatico-duodenal arteries, a nd must innervate the pancreas as the preganglionic nerve fiber.