146 JOHN S. BARLOW 



The early plaques of demyelination in multiple sclerosis appear pre- 

 ponderantly around small veins (Adams and Kubik, 1952), and a similar 

 localization appears for the demyelinative lesions of experimental allergic 

 encephalomyelitis in some animals (Mc Alpine et al., 1955; Waksman, 1960). 

 Further, induction of the lesions of the latter disease in predetermined loca- 

 tions in the brain by use of physical agents has been reported by Clark and 

 Bogdanove (1955). It might be of interest to determine whether lesions of 

 experimental allergic encephalomyelitis could also be induced in predeter- 

 mined locations by low doses of radiation from well focused beams of high 

 energy particles (for example, of appropriately filtered high energy protons). 

 Perivenous staining with trypan blue has been rep>orted in the demyelinative 

 plaques of multiple sclerosis (Broman, 1949) and in lesions of experimental 

 allergic encephalomyelitis in animals (Barlow, 1956; Waksman, 1960) ; a 

 similar focal staining might be looked for following focused irradiation at 

 low doses, since it is a known finding with much larger doses (Clemente and 

 Hoist, 1954) . Should positive results be found from either of these experi- 

 ments, a possible protective eflfort might be explored for some of the agents 

 (e.g., cysteine) which are known to lessen the biological effects of ionizing 

 radiation. 



If place of residence early in life is the imp>ortant factor, then possible 

 relationships (direct or indirect) might be explored between radiation and 

 immunochemical processes in early life which might underlie demyelinative 

 processes in adult life. 



In connection with the experiments outlined, it should be noted that if 

 cosmic radiation is at all related to multiple sclerosis, the mechanism of its 

 action is likely to be different from the biologic effects of cosmic rays at high 

 altitudes (Yagoda, 1957; Schaefer, 1958). 



Finally, the possibility should be kept in mind that some other factors 

 (for example, certain types of infections, perhaps not known) might act as 

 intermediaries between cosmic rays and multiple sclerosis. 



Summary and Conclusions 



Multiple sclerosis appears to exhibit a fairly well marked geographic dis- 

 tribution, being appreciably more frequent in northern than in southern 

 latitudes in certain areas of the world. It is generally agreed that this geo- 

 graphic distribution must be taken into account in any satisfactory theory 

 of etiology of the disease. Possible correlates of the geographic distribution 

 which previously have been advanced have not appeared entirely satisfactory; 

 certainly geographic latitude itself appears to be a poor correlate. Several 

 independent sets of statistics on the distribution of the disease were examined 

 from the standpoint of geomagnetic latitude, a parameter that is related to 



