THE STRUCTURE OF THE SYNAPSE IN THE LATERAL GENICULATE BODY

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Abstract
An investigation into the synapses of the lateral geniculate body of the cat, with the aid of the Golgi method, neurofibrillar staining, secondary degeneration and electron microscope analysis, shows the main articulation in the optic pathway to be effected by a peculiar kind of axodendritic contact. These synapses resemble the glomerular synapse in the granular zone of the cerebellar cortex and consist of claw-shaped presynaptic endings of optic fibres in close contact with spheroid protrusions of peripheral parts of the nerve cell dendrites or their grape-like apical arborizations. The dendritic protrusions are often impressed, sometimes even invaginated into presynaptic endings. As terminal branches of different optic fibres may participate in the same geniculate "glomerular" synapse as well as the dendrites of several different nerve cells, this mode of linkage secures divergence as well as a considerable degree of convergence. With appropriate degeneration technique numerous nonoptic synapses are found in the geniculate body. They are partly axo-somatic end-feet (not very frequent), axo-dendritic contacts of a very small calibre terminal fibre system on the dendrites, generally localized more proximally than the parts involved in the glomeruli and some non optic elements involved in the glomeruli themselves.