Neuro-insular complex type I in the mouse. Re-evaluation of the pancreatic islet as a modified ganglion

Autonomic ganglia in the pancreas may include islet cells; while islets sometimes contain a group of ganglion cells. Electron microscope observation in adult mice confirms occurrence of a structure called neuro-insular complex type I by Fujita (1959), in which islet cells are juxtaposed to nerve cells either directly or by intercalation of a thin glial cell cytoplasm. Islet cells are equivalent to neurons in their attitude towards neurons and towards glial elements in the neuro-insular complex. There seems to be every gradation between pure ganglia, mixed forms representing the neuro-insular complexes, and pure islets. Pancreatic islets may thus be regarded as modified ganglia.