[Different types of secondary degeneration of visual nerve endings in the midbrain tectum of the steppe turtle]

Along with the commonly known patterns of terminal destruction ("dark", "light", "neurofilamentous"), new types of changes have been revealed, referred to as "vesicular" and "glycogen" trasformation types. Vesicular transformation which may develop according to the dark or light type is characterized by a sharp deformation of synaptic vesicles; glycogen transformation is distinguished by agglutination and disappearance of synaptic vesicles, the inside of the terminal being filled up with glycogen granules. Ultrastructural differences of the terminal degeneration process in different groups of nerve fibers reflect the morpho-functional heterogeneity of the retina ganglion cells and of their axons.