GEOGRAPHIC DISTRIBUTION OF MULTIPLE SCLEROSIS 



141 



0.8 



0.4 



20 30 40 



Geomagnetic latitude 



Fig. 10. Vertical flux of cosmic ray particles near the top of the atmosphere. (After 

 Curtis, 1956, and from Puppi and Dallaporta, 1952.) 



e48.3 



100^==* 



Fig. 11. Dependence of primary cosmic ray intensity on magnetic latitude (\). 

 The ordinate represents the relative intensity for each of the various energies {p = 

 energy of protons in billions of electron-volts; other parameters shown on the cur\'es 

 are not relevant to the present discussion), expressed as the per cent of the maximum 

 possible intensity for that particular energy. (From Richtmyer et al., 1955, and adapted 

 from Lemaitre and Vallarta. 1933.) 



protons appears just before the end of their trajectory (Malis et al., 1957). 

 However, the number of protons of a similar terminal energy at the surface 

 of the earth which have been produced by the complex interaction of 

 primary cosmic rays with the atmosphere is far greater than the number of 



