Time dependence of terminal degeneration in spino-cerebellar mossy fiber rosettes in the chicken and the application of terminal degeneration in successive degeneration experiments.

Mossy fiber rosettes in the granular layer of the cerebellar cortex were studied after sections of the lateral funiculus of the spinal cord of the chicken and silver impregnation with the Fink-Heimer ('67) method I. After a survival time of two or three days two types of degenerated rosettes were found. The first type is characterized by digitiform protrusions, the second type of rosette is spherical. Both types are covered by small argyrophilic particles which disappear when the degeneration proceeds. With longer survival times the rosettes become swollen and finally disintegrate and lose their argyrophilia. After a survival time of 30 days only debris of rosettes can be found. These observations were used to determine the cerebellar cortical projection mossy fibers originating from segments of the spinal cord isolated in "successive degeneration" experiments consisting of a chronic cordotomy followed by an acute cordotomy rostral to the first one.