THERE IS much controversy over the proper treatment of acute and chronic spinal cord compression. Not everyone agrees, for instance, on the best time to operate in cases of acute compression of the spinal cord or cauda equina, or whether to operate at all. Some of the signs and symptoms accompanying these lesions, moreover, are perplexing, and even misleading. Kahn1has called attention to the primary lateral sclerosis syndrome resulting from anterior spinal cord compression. Only recently, indeed, several well-known neurologists made a diagnosis of primary lateral sclerosis in a quadriplegic woman. At operation, however, one of us (I. M. T.) removed a ventrally placed meningioma from the cervical portion of her spinal cord. On occasion, also, "neoplasms may simulate subacute combined degeneration of the spinal cord."2 In an effort to throw light on these problems, we have submitted them to experimental analysis in laboratory animals. The project