Morphological changes in the small intestine of the cat following transection of the vagal nerve.

An attempt was made to identify the vagal fibres of the small intestine and to investigate their course by secondary degeneration after transection of both vagus nerves just below the ganglion nodosum. Under the electron microscope, degenerated fibres could be observed in the myenteric and submucous plexuses, in the longitudinal and circular muscular coats of the duodenum and jejunum. No signs of degeneration were encountered in the wall of the ileum. Direct synaptic relationship between these degenerated fibres and the nerve cells and intact nerve processes could scarcely be found. The degenerated axons do not differ basically from other, intrinsic nerve processes containing round clear vesicles (30--60 nm in diameter) and granular vesicles (80--120 nm in diameter). The sporadic occurrence of the degenerated axons on the surface of cell somata and processes might indicate that the vagal nerve innervates only a few neurons in the small intestine and that the intrinsic neurons contact a large number of other neurons via processes in the intestinal wall. The vagal nerve fibres thus seem to have a modulatory effect on the activity of the intestinal wall.