Distribution of Vagus and Sacral Nerves to the Large Intestine

Abstract

There still remains considerable disagreement regarding the distribution of vagus and sacral nerves to the large intestine. According to Klee 1 vagus fibers do not reach the large intestine. Carlson 2 has recently reported experiments in which stimulation of the sacral nerves in the dog caused contraction of the circular and longitudinal muscle of the entire colon.

The present experimental anatomical investigation was carried out on cats and dogs. The vagus and sacral nerves respectively were sectioned in 2 groups of animals. Three weeks after operation the animals were killed and the large intestines were removed and studied both macro- and microscopically. Pyridine silver sections were made from 3 levels; viz., the ascending colon, the distal half of the transverse colon, and the middle portion of the descending colon.

Pyridine silver sections from the corresponding levels of the normally innervated large intestine reveal longitudinal nerve fiber bundles in the serous layer, which increase in size and number toward the distal end.

Pyridine silver sections from the large intestine of animals in which the vagi were sectioned just below the diaphragm showed degenerated nerve fiber bundles in the ascending and transverse portions of the colon. These obviously are vagus fibers. They are less numerous in the transverse than in the ascending colon. No evidence of degenerated nerve fibers was observed in sections of the descending colon. These results indicate that vagus fibers are distributed to the large intestine at least as far as the distal portion of the transverse colon.

A study of the pyridine silver sections from the same levels of the large intestine of animals in which all the sacral nerves were sectioned, revealed degenerative changes throughout the entire large intestine.