| Abstract
| - The walls of the digestive tract of mice were fixed in osmium tetroxide, embedded in styrene-methacrylate, and sectioned for electron microscopy. The examination of sections of Auerbach's plexus revealed the presence of two types of synaptic nerve processes. They are enclosed on the outer surface by delicate plasma membranes, typically contain varying quantities of synaptic vesicles and mitochondria, and lie in close apposition to the surface of perikarya or processes of the local neurons. In one type the synaptic nerve process contains numerous agranular vesicles, relatively uniform in size (about 450 Å in diameter), lying in clusters polarized toward the closely apposed dense area of the synaptic membranes. In the other type all the numerous vesicles in the nerve processes are granular and larger (about 830 Å in diameter) and each contains a dense central granule about 450 Å in diameter. At the synaptic junction, some of the vesiculated processes display a small protrusion which fits in a small pit of the postsynaptic area of the local neuron. Sometimes the large canalicular structure in the cytoplasm of local neurons has an opening in the synaptic cleft.
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