Subacute combined degeneration of the cord and amyotrophic lateral sclerosis are distinct morbid entities, each possessing a pathologic picture of its own. In the former, the histologic changes are represented by degeneration of the posterolateral columns; in the latter, by that of the corticomuscular system of nerve fibers, extending from the motor cortex through the spinal cord and peripheral nerves to the muscles. In subacute degeneration of the cord the process is a so-called primary degeneration, originating in the nerve fibers themselves; in amyotrophic lateral sclerosis the degeneration is secondary, originating in the motor ganglion cells of the cortex, medulla and anterior horns of the spinal cord. While either condition in its typical and uncomplicated form offers no diagnostic difficulties, it is not so in cases that, like the one presented here, are atypical and complicated. REPORT OF CASE Clinical History. —An Italian man, aged 48, with a good personal