GEOGRAPHIC DISTRIBUTION OF MULTIPLE SCLEROSIS 



131 



same team of observers for the two latitudes studied and similar diagnostic 

 criteria (Alter et al., 1960; Okinaka et al., 1960). Additional details for 

 these two surveys are shown in Table III, with prevalences relative to that 

 for Halifax. Plots for this table are reproduced in Fig. 4, and it is evident 

 that for these two surveys the geomagnetic coordinate provides a much better 

 parameter than does the geographic coordinate, a conclusion not appreciably 

 altered by assumption of a reference prevalence of 33.6 per 100,000 popula- 

 tion instead of the 48 per 100,000 of Fig. 3 or of 42 per 100,000 of Fig. 2. 

 Moreover, it is apparent that the sigmoid curve in the previous geomagnetic 

 plots is also a good fit for this plot in Fig. 4. 



Multiple Sclerosis in the Soviet Union 



Because of its considerable geographic extent, data on the occurrence of 

 multiple sclerosis in the Soviet Union would be of considerable interest. 

 Grashchenkov and his associates (1960) have recently investigated the mor- 

 bidity due to this disease in different regions of the Soviet Union by com- 

 parison of the percentages of cases of multiple sclerosis in relation to the 

 total number of patients of sei^vices of neurology during 1948-1957 (Table 

 IV) . Such data on the relative frequency of a disease are not directly com- 

 parable with mortality statistics or prevalence data for other areas of the 



1.2 



1.0 



k 



K 0.2 



0.8 



0.6 



0.4 



0.0 



X-K) 



X-*o 



30 40 50 60 70 



GEOGRAPHIC LATITUDE 'N 



20 30 40 50 60 70 



GEOMAGNETIC LATITUDE 'N 



Fig. 5. Relative number of hospital admissions for multiple sclerosis in selected 

 communities in the Soviet Union (see Table IV). 



