Electron-microscopic identification of Marchi-positive bodies and argyrophilic granules in the spinal cord white matter of the guinea pig.

Sections from spinal cord white matter of normal and rhizotomized guinea pigs fixed by glutaraldehyde perfusion were stained with Marchi fluid or according to a suppressive silver technique. With the aid of the section-embedding method thin sections, cut from light-microscopically identified areas containing Marchi-positive bodies or argyrophilic granules, were examined in the electron microscope. The results show that the Marchi-positive bodies and argyrophilic granules, which are present in normal white matter, represent different histochemical expressions of the same entity--the myelinoid body. In view of the similarities between myelinoid bodies and myelin fragments formed during Wallerian degeneration it is suggested that this type of so called artifact staining of normal white matter inherent to both methods should instead be considered as an expression of a specificity of the two methods for degenerating nervous elements.