As difined in the first part of these papers, the distribution of MS does not really correlate well with broad geoclimatic factors. Specifically there is little evidence for a direct correlation with latitude, and such correlations, to be meaningful, need to consider longitude as well. At latitude 40 degrees north, for example, MS is high frequency in America, medium in Europe, and low in Asia. Accordingly the world-wide distribution of MS is best regarded as comprising three bands or zones of high medium, and low risk or frequency as delineated here. All the high and medium regions are at present found in Europe or in areas colonized by Europeans. It seems likely then that MS originated in western Europe and has spread from there to the United States and Canada as well as to New Zealand and Australia. The disorder may well have "taken" also in South Africa and Hawaii, but at considerably lower levels. Further attention to the character and timing of the depresion of this disease may well provide clues vital to determining its cause.