The presence of vagus fibers in the splanchnic nerve of the cat.

Abstract

The recent announcement by Iwama 1 that a considerable number of medullated fibers from the vagus enter the sympathetic trunk near the inferior cervical ganglion, especially on the right side, and that some of these fibers run into the abdominal viscera via the splanchnic nerves, immediately brings into question considerable visceral neurology based upon experimental stimulation of the splanchnic and the vagus in the cat, at least. According to Iwama's observations it is impossible to stimulate the right splanchnic of the cat without also stimulating some vagus fibers.

It also occurred to us that there might be enough variability in number of vagus fibers that reach the gastric regions through the splanchnic nerves of different species of animals to be a factor in the results obtained by Carlson and others 2 following stimulation of the peripheral end of the splanchnic, such as only inhibition of the cardia in the rabbit and either contraction or inhibition in the cat depending on the state of tonus at the time of stimulation.

The preliminary work necessary to get this question upon a quantitative basis gave results at such variance with those expected that this note is deemed advisable although only four cats and two rabbits of our series bear directly on the subject.

Section of the right vagus in the mid-cervical region of the rabbits produced no Wallerian degeneration in the thoracic sympathetic trunk and hence none in the splanchnic nerves.

In three cats (right vagus cut in two and left vagus in one) results were similarly negative. In a fourth cat, however, with right vagus cut above the anastomosis with the inferior cervical sympathetic ganglion, two degenerated medullated fibers were clearly identified in the right thoracic sympathetic trunk above the origin of the splanchnic nerve.