Silver impregnation method for neurons and myelinated axons of acult central nervous system

A new method has been developed for silver impregnation of neurons and myelinated axons in the cerebral cortex of the adult dog. By this method principal types of neurons including pyramidal, stellate, fusiform, horizontal neurons of Layer I, and special auditory neurons are colored black with a clear background, while myelinated fibers in the same piece of tissue are colored yellow. The yellow hue appears limited to the myelin sheath. Meyelinated axons of all sizes in the molecular layer, radial bundles, and deep tangential strata accept the stain. Comparison with data from other experiments indicates that osmium tetroxide inhibits the yellow staining of the myelinated axons, and that formaldehyde promotes such staining in conjunction with ammonium ions and sucrose.