Neuritic growth and neuroma formation by an isolated molluscan ganglion

The isolated, paired buccal ganglia of the snail Helisoma trivolvis were cultured in vivo (i.e., in host snails) for periods up to 377 days. Such ganglia typically become enveloped in a white mass of fibrous tissue which reaches a maximum plateau of size within four weeks. The scanning electron microscope revealed the newly formed tissue to be composed of fine fibers which also pervaded the neuropil. Injection of individual neurons with Lucifer Yellow CH filled many new neurites within the tissue mass. It is concluded that these masses are largely of neuronal origin and they are therefore designated as neuromas. The maximum size of neuromas may be limited by intrinsic mechanisms which limit neuronal volume.