GEOGRAPHIC DISTRIBUTION OF MULTIPLE SCLEROSIS 147 



the earth's magnetic axis in the same way that geographic latitude is related 

 to the earth's axis of rotation. That the distribution of multiple sclerosis 

 might be examined in this way was suggested by the fact that a variation 

 with geomagnetic latitude is well known for the intensity of cosmic rays. 

 The frequencies of the disease in widely separated areas were found to vary 

 in a systematic manner with geomagnetic latitude; therefore, the possibility 

 arises that cosmic rays in some way might be a factor in the occurrence of 

 the disease. The latitude distribution for the disease bears some resemblance 

 to that for a particular component of the primary cosmic radiation at the 

 top of the atmophere; no similarly good correlate is apparent, however, 

 among the various cosmic ray components at the surface of the earth, hence 

 the similarity may be entirely fortuitous. Some possible intermediary factors 

 examined appear to offer no great promise. A world map, on which is indi- 

 cated the expected geographic distribution of multiple sclerosis on the basis 

 of geomagnetic latitude, is presented for comparison with results of future 

 surveys on the disease so that the present results may be evaluated further. 



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