The incubation period of multiple sclerosis.

Movement of myelin through the spiral laminar arrangement of the myelin sheaths of neurones might act as a biological clock in determining the prolonged incubation period of multiple sclerosis. A defect incorporated peripherally in the myelin sheath as a result of neonatal virus infection might be revealed years later when the defective myelin reaches the axolemma and provokes an immunological reaction. This process could, directly or indirectly, be prevented by the effects of solar radiation, thus accounting for the geographical distribution of the disease.