The recognition of multiple neuritis as a distinct morbid entity dates back only twenty years, when the clinical and anatomic characters of the disorder were first fully pointed out by Leyden. Previously the symptoms had been attributed to lesions of the spinal cord; but in the small number of cases in which post-mortem examination could be made these alterations were not found. It has since been learned that polyneuritis may result from traumatic influences, in the course of infectious diseases, and from the action of various poisons. Exposure to cold acts probably as a contributory factor, merely lowering vitality and thus favoring the invasion of micro-organisms.
Chronic alcoholism is probably the most important etiologic factor, and under such circumstances the disorder has been observed to appear in three forms, in which motor, sensory and ataxic symptoms have respectively predominated. The motor, or paralytic, or amyotrophic variety is by far the