54 healthy cats were studied. In almost all cases, two types of degenerative signs could be seen: in the primary optic pathways, but also in the posterior funiculi and the spinalcerebellar tracts, lesions of wide-diameter axons seen by their initial demyelination, accompanied by intense neurogJial reactions, and, on the other hand, a Wallerian degeneration of smaller axons situated in the axial part of the nerve. The percentage of these abnormalities must still be evaluated. Their eventual consequences and nature are discussed.